1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
  24  * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
  25  */
  26 
  27 #include <sys/zfs_context.h>
  28 #include <sys/fm/fs/zfs.h>
  29 #include <sys/spa.h>
  30 #include <sys/txg.h>
  31 #include <sys/spa_impl.h>
  32 #include <sys/vdev_impl.h>
  33 #include <sys/zio_impl.h>
  34 #include <sys/zio_compress.h>
  35 #include <sys/zio_checksum.h>
  36 #include <sys/dmu_objset.h>
  37 #include <sys/arc.h>
  38 #include <sys/ddt.h>
  39 #include <sys/blkptr.h>
  40 #include <sys/zfeature.h>
  41 
  42 /*
  43  * ==========================================================================
  44  * I/O type descriptions
  45  * ==========================================================================
  46  */
  47 const char *zio_type_name[ZIO_TYPES] = {
  48         "zio_null", "zio_read", "zio_write", "zio_free", "zio_claim",
  49         "zio_ioctl"
  50 };
  51 
  52 /*
  53  * ==========================================================================
  54  * I/O kmem caches
  55  * ==========================================================================
  56  */
  57 kmem_cache_t *zio_cache;
  58 kmem_cache_t *zio_link_cache;
  59 kmem_cache_t *zio_buf_cache[SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT];
  60 kmem_cache_t *zio_data_buf_cache[SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT];
  61 
  62 #ifdef _KERNEL
  63 extern vmem_t *zio_alloc_arena;
  64 #endif
  65 
  66 #define ZIO_PIPELINE_CONTINUE           0x100
  67 #define ZIO_PIPELINE_STOP               0x101
  68 
  69 /*
  70  * The following actions directly effect the spa's sync-to-convergence logic.
  71  * The values below define the sync pass when we start performing the action.
  72  * Care should be taken when changing these values as they directly impact
  73  * spa_sync() performance. Tuning these values may introduce subtle performance
  74  * pathologies and should only be done in the context of performance analysis.
  75  * These tunables will eventually be removed and replaced with #defines once
  76  * enough analysis has been done to determine optimal values.
  77  *
  78  * The 'zfs_sync_pass_deferred_free' pass must be greater than 1 to ensure that
  79  * regular blocks are not deferred.
  80  */
  81 int zfs_sync_pass_deferred_free = 2; /* defer frees starting in this pass */
  82 int zfs_sync_pass_dont_compress = 5; /* don't compress starting in this pass */
  83 int zfs_sync_pass_rewrite = 2; /* rewrite new bps starting in this pass */
  84 
  85 /*
  86  * An allocating zio is one that either currently has the DVA allocate
  87  * stage set or will have it later in its lifetime.
  88  */
  89 #define IO_IS_ALLOCATING(zio) ((zio)->io_orig_pipeline & ZIO_STAGE_DVA_ALLOCATE)
  90 
  91 boolean_t       zio_requeue_io_start_cut_in_line = B_TRUE;
  92 
  93 #ifdef ZFS_DEBUG
  94 int zio_buf_debug_limit = 16384;
  95 #else
  96 int zio_buf_debug_limit = 0;
  97 #endif
  98 
  99 void
 100 zio_init(void)
 101 {
 102         size_t c;
 103         vmem_t *data_alloc_arena = NULL;
 104 
 105 #ifdef _KERNEL
 106         data_alloc_arena = zio_alloc_arena;
 107 #endif
 108         zio_cache = kmem_cache_create("zio_cache",
 109             sizeof (zio_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
 110         zio_link_cache = kmem_cache_create("zio_link_cache",
 111             sizeof (zio_link_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
 112 
 113         /*
 114          * For small buffers, we want a cache for each multiple of
 115          * SPA_MINBLOCKSIZE.  For larger buffers, we want a cache
 116          * for each quarter-power of 2.
 117          */
 118         for (c = 0; c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; c++) {
 119                 size_t size = (c + 1) << SPA_MINBLOCKSHIFT;
 120                 size_t p2 = size;
 121                 size_t align = 0;
 122                 size_t cflags = (size > zio_buf_debug_limit) ? KMC_NODEBUG : 0;
 123 
 124                 while (p2 & (p2 - 1))
 125                         p2 &= p2 - 1;
 126 
 127 #ifndef _KERNEL
 128                 /*
 129                  * If we are using watchpoints, put each buffer on its own page,
 130                  * to eliminate the performance overhead of trapping to the
 131                  * kernel when modifying a non-watched buffer that shares the
 132                  * page with a watched buffer.
 133                  */
 134                 if (arc_watch && !IS_P2ALIGNED(size, PAGESIZE))
 135                         continue;
 136 #endif
 137                 if (size <= 4 * SPA_MINBLOCKSIZE) {
 138                         align = SPA_MINBLOCKSIZE;
 139                 } else if (IS_P2ALIGNED(size, p2 >> 2)) {
 140                         align = MIN(p2 >> 2, PAGESIZE);
 141                 }
 142 
 143                 if (align != 0) {
 144                         char name[36];
 145                         (void) sprintf(name, "zio_buf_%lu", (ulong_t)size);
 146                         zio_buf_cache[c] = kmem_cache_create(name, size,
 147                             align, NULL, NULL, NULL, NULL, NULL, cflags);
 148 
 149                         /*
 150                          * Since zio_data bufs do not appear in crash dumps, we
 151                          * pass KMC_NOTOUCH so that no allocator metadata is
 152                          * stored with the buffers.
 153                          */
 154                         (void) sprintf(name, "zio_data_buf_%lu", (ulong_t)size);
 155                         zio_data_buf_cache[c] = kmem_cache_create(name, size,
 156                             align, NULL, NULL, NULL, NULL, data_alloc_arena,
 157                             cflags | KMC_NOTOUCH);
 158                 }
 159         }
 160 
 161         while (--c != 0) {
 162                 ASSERT(zio_buf_cache[c] != NULL);
 163                 if (zio_buf_cache[c - 1] == NULL)
 164                         zio_buf_cache[c - 1] = zio_buf_cache[c];
 165 
 166                 ASSERT(zio_data_buf_cache[c] != NULL);
 167                 if (zio_data_buf_cache[c - 1] == NULL)
 168                         zio_data_buf_cache[c - 1] = zio_data_buf_cache[c];
 169         }
 170 
 171         zio_inject_init();
 172 }
 173 
 174 void
 175 zio_fini(void)
 176 {
 177         size_t c;
 178         kmem_cache_t *last_cache = NULL;
 179         kmem_cache_t *last_data_cache = NULL;
 180 
 181         for (c = 0; c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; c++) {
 182                 if (zio_buf_cache[c] != last_cache) {
 183                         last_cache = zio_buf_cache[c];
 184                         kmem_cache_destroy(zio_buf_cache[c]);
 185                 }
 186                 zio_buf_cache[c] = NULL;
 187 
 188                 if (zio_data_buf_cache[c] != last_data_cache) {
 189                         last_data_cache = zio_data_buf_cache[c];
 190                         kmem_cache_destroy(zio_data_buf_cache[c]);
 191                 }
 192                 zio_data_buf_cache[c] = NULL;
 193         }
 194 
 195         kmem_cache_destroy(zio_link_cache);
 196         kmem_cache_destroy(zio_cache);
 197 
 198         zio_inject_fini();
 199 }
 200 
 201 /*
 202  * ==========================================================================
 203  * Allocate and free I/O buffers
 204  * ==========================================================================
 205  */
 206 
 207 /*
 208  * Use zio_buf_alloc to allocate ZFS metadata.  This data will appear in a
 209  * crashdump if the kernel panics, so use it judiciously.  Obviously, it's
 210  * useful to inspect ZFS metadata, but if possible, we should avoid keeping
 211  * excess / transient data in-core during a crashdump.
 212  */
 213 void *
 214 zio_buf_alloc(size_t size)
 215 {
 216         size_t c = (size - 1) >> SPA_MINBLOCKSHIFT;
 217 
 218         ASSERT3U(c, <, SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT);
 219 
 220         return (kmem_cache_alloc(zio_buf_cache[c], KM_PUSHPAGE));
 221 }
 222 
 223 /*
 224  * Use zio_data_buf_alloc to allocate data.  The data will not appear in a
 225  * crashdump if the kernel panics.  This exists so that we will limit the amount
 226  * of ZFS data that shows up in a kernel crashdump.  (Thus reducing the amount
 227  * of kernel heap dumped to disk when the kernel panics)
 228  */
 229 void *
 230 zio_data_buf_alloc(size_t size)
 231 {
 232         size_t c = (size - 1) >> SPA_MINBLOCKSHIFT;
 233 
 234         ASSERT(c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT);
 235 
 236         return (kmem_cache_alloc(zio_data_buf_cache[c], KM_PUSHPAGE));
 237 }
 238 
 239 void
 240 zio_buf_free(void *buf, size_t size)
 241 {
 242         size_t c = (size - 1) >> SPA_MINBLOCKSHIFT;
 243 
 244         ASSERT(c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT);
 245 
 246         kmem_cache_free(zio_buf_cache[c], buf);
 247 }
 248 
 249 void
 250 zio_data_buf_free(void *buf, size_t size)
 251 {
 252         size_t c = (size - 1) >> SPA_MINBLOCKSHIFT;
 253 
 254         ASSERT(c < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT);
 255 
 256         kmem_cache_free(zio_data_buf_cache[c], buf);
 257 }
 258 
 259 /*
 260  * ==========================================================================
 261  * Push and pop I/O transform buffers
 262  * ==========================================================================
 263  */
 264 static void
 265 zio_push_transform(zio_t *zio, void *data, uint64_t size, uint64_t bufsize,
 266         zio_transform_func_t *transform)
 267 {
 268         zio_transform_t *zt = kmem_alloc(sizeof (zio_transform_t), KM_SLEEP);
 269 
 270         zt->zt_orig_data = zio->io_data;
 271         zt->zt_orig_size = zio->io_size;
 272         zt->zt_bufsize = bufsize;
 273         zt->zt_transform = transform;
 274 
 275         zt->zt_next = zio->io_transform_stack;
 276         zio->io_transform_stack = zt;
 277 
 278         zio->io_data = data;
 279         zio->io_size = size;
 280 }
 281 
 282 static void
 283 zio_pop_transforms(zio_t *zio)
 284 {
 285         zio_transform_t *zt;
 286 
 287         while ((zt = zio->io_transform_stack) != NULL) {
 288                 if (zt->zt_transform != NULL)
 289                         zt->zt_transform(zio,
 290                             zt->zt_orig_data, zt->zt_orig_size);
 291 
 292                 if (zt->zt_bufsize != 0)
 293                         zio_buf_free(zio->io_data, zt->zt_bufsize);
 294 
 295                 zio->io_data = zt->zt_orig_data;
 296                 zio->io_size = zt->zt_orig_size;
 297                 zio->io_transform_stack = zt->zt_next;
 298 
 299                 kmem_free(zt, sizeof (zio_transform_t));
 300         }
 301 }
 302 
 303 /*
 304  * ==========================================================================
 305  * I/O transform callbacks for subblocks and decompression
 306  * ==========================================================================
 307  */
 308 static void
 309 zio_subblock(zio_t *zio, void *data, uint64_t size)
 310 {
 311         ASSERT(zio->io_size > size);
 312 
 313         if (zio->io_type == ZIO_TYPE_READ)
 314                 bcopy(zio->io_data, data, size);
 315 }
 316 
 317 static void
 318 zio_decompress(zio_t *zio, void *data, uint64_t size)
 319 {
 320         if (zio->io_error == 0 &&
 321             zio_decompress_data(BP_GET_COMPRESS(zio->io_bp),
 322             zio->io_data, data, zio->io_size, size) != 0)
 323                 zio->io_error = SET_ERROR(EIO);
 324 }
 325 
 326 /*
 327  * ==========================================================================
 328  * I/O parent/child relationships and pipeline interlocks
 329  * ==========================================================================
 330  */
 331 /*
 332  * NOTE - Callers to zio_walk_parents() and zio_walk_children must
 333  *        continue calling these functions until they return NULL.
 334  *        Otherwise, the next caller will pick up the list walk in
 335  *        some indeterminate state.  (Otherwise every caller would
 336  *        have to pass in a cookie to keep the state represented by
 337  *        io_walk_link, which gets annoying.)
 338  */
 339 zio_t *
 340 zio_walk_parents(zio_t *cio)
 341 {
 342         zio_link_t *zl = cio->io_walk_link;
 343         list_t *pl = &cio->io_parent_list;
 344 
 345         zl = (zl == NULL) ? list_head(pl) : list_next(pl, zl);
 346         cio->io_walk_link = zl;
 347 
 348         if (zl == NULL)
 349                 return (NULL);
 350 
 351         ASSERT(zl->zl_child == cio);
 352         return (zl->zl_parent);
 353 }
 354 
 355 zio_t *
 356 zio_walk_children(zio_t *pio)
 357 {
 358         zio_link_t *zl = pio->io_walk_link;
 359         list_t *cl = &pio->io_child_list;
 360 
 361         zl = (zl == NULL) ? list_head(cl) : list_next(cl, zl);
 362         pio->io_walk_link = zl;
 363 
 364         if (zl == NULL)
 365                 return (NULL);
 366 
 367         ASSERT(zl->zl_parent == pio);
 368         return (zl->zl_child);
 369 }
 370 
 371 zio_t *
 372 zio_unique_parent(zio_t *cio)
 373 {
 374         zio_t *pio = zio_walk_parents(cio);
 375 
 376         VERIFY(zio_walk_parents(cio) == NULL);
 377         return (pio);
 378 }
 379 
 380 void
 381 zio_add_child(zio_t *pio, zio_t *cio)
 382 {
 383         zio_link_t *zl = kmem_cache_alloc(zio_link_cache, KM_SLEEP);
 384 
 385         /*
 386          * Logical I/Os can have logical, gang, or vdev children.
 387          * Gang I/Os can have gang or vdev children.
 388          * Vdev I/Os can only have vdev children.
 389          * The following ASSERT captures all of these constraints.
 390          */
 391         ASSERT(cio->io_child_type <= pio->io_child_type);
 392 
 393         zl->zl_parent = pio;
 394         zl->zl_child = cio;
 395 
 396         mutex_enter(&cio->io_lock);
 397         mutex_enter(&pio->io_lock);
 398 
 399         ASSERT(pio->io_state[ZIO_WAIT_DONE] == 0);
 400 
 401         for (int w = 0; w < ZIO_WAIT_TYPES; w++)
 402                 pio->io_children[cio->io_child_type][w] += !cio->io_state[w];
 403 
 404         list_insert_head(&pio->io_child_list, zl);
 405         list_insert_head(&cio->io_parent_list, zl);
 406 
 407         pio->io_child_count++;
 408         cio->io_parent_count++;
 409 
 410         mutex_exit(&pio->io_lock);
 411         mutex_exit(&cio->io_lock);
 412 }
 413 
 414 static void
 415 zio_remove_child(zio_t *pio, zio_t *cio, zio_link_t *zl)
 416 {
 417         ASSERT(zl->zl_parent == pio);
 418         ASSERT(zl->zl_child == cio);
 419 
 420         mutex_enter(&cio->io_lock);
 421         mutex_enter(&pio->io_lock);
 422 
 423         list_remove(&pio->io_child_list, zl);
 424         list_remove(&cio->io_parent_list, zl);
 425 
 426         pio->io_child_count--;
 427         cio->io_parent_count--;
 428 
 429         mutex_exit(&pio->io_lock);
 430         mutex_exit(&cio->io_lock);
 431 
 432         kmem_cache_free(zio_link_cache, zl);
 433 }
 434 
 435 static boolean_t
 436 zio_wait_for_children(zio_t *zio, enum zio_child child, enum zio_wait_type wait)
 437 {
 438         uint64_t *countp = &zio->io_children[child][wait];
 439         boolean_t waiting = B_FALSE;
 440 
 441         mutex_enter(&zio->io_lock);
 442         ASSERT(zio->io_stall == NULL);
 443         if (*countp != 0) {
 444                 zio->io_stage >>= 1;
 445                 zio->io_stall = countp;
 446                 waiting = B_TRUE;
 447         }
 448         mutex_exit(&zio->io_lock);
 449 
 450         return (waiting);
 451 }
 452 
 453 static void
 454 zio_notify_parent(zio_t *pio, zio_t *zio, enum zio_wait_type wait)
 455 {
 456         uint64_t *countp = &pio->io_children[zio->io_child_type][wait];
 457         int *errorp = &pio->io_child_error[zio->io_child_type];
 458 
 459         mutex_enter(&pio->io_lock);
 460         if (zio->io_error && !(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE))
 461                 *errorp = zio_worst_error(*errorp, zio->io_error);
 462         pio->io_reexecute |= zio->io_reexecute;
 463         ASSERT3U(*countp, >, 0);
 464 
 465         (*countp)--;
 466 
 467         if (*countp == 0 && pio->io_stall == countp) {
 468                 pio->io_stall = NULL;
 469                 mutex_exit(&pio->io_lock);
 470                 zio_execute(pio);
 471         } else {
 472                 mutex_exit(&pio->io_lock);
 473         }
 474 }
 475 
 476 static void
 477 zio_inherit_child_errors(zio_t *zio, enum zio_child c)
 478 {
 479         if (zio->io_child_error[c] != 0 && zio->io_error == 0)
 480                 zio->io_error = zio->io_child_error[c];
 481 }
 482 
 483 /*
 484  * ==========================================================================
 485  * Create the various types of I/O (read, write, free, etc)
 486  * ==========================================================================
 487  */
 488 static zio_t *
 489 zio_create(zio_t *pio, spa_t *spa, uint64_t txg, const blkptr_t *bp,
 490     void *data, uint64_t size, zio_done_func_t *done, void *private,
 491     zio_type_t type, zio_priority_t priority, enum zio_flag flags,
 492     vdev_t *vd, uint64_t offset, const zbookmark_phys_t *zb,
 493     enum zio_stage stage, enum zio_stage pipeline)
 494 {
 495         zio_t *zio;
 496 
 497         ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
 498         ASSERT(P2PHASE(size, SPA_MINBLOCKSIZE) == 0);
 499         ASSERT(P2PHASE(offset, SPA_MINBLOCKSIZE) == 0);
 500 
 501         ASSERT(!vd || spa_config_held(spa, SCL_STATE_ALL, RW_READER));
 502         ASSERT(!bp || !(flags & ZIO_FLAG_CONFIG_WRITER));
 503         ASSERT(vd || stage == ZIO_STAGE_OPEN);
 504 
 505         zio = kmem_cache_alloc(zio_cache, KM_SLEEP);
 506         bzero(zio, sizeof (zio_t));
 507 
 508         mutex_init(&zio->io_lock, NULL, MUTEX_DEFAULT, NULL);
 509         cv_init(&zio->io_cv, NULL, CV_DEFAULT, NULL);
 510 
 511         list_create(&zio->io_parent_list, sizeof (zio_link_t),
 512             offsetof(zio_link_t, zl_parent_node));
 513         list_create(&zio->io_child_list, sizeof (zio_link_t),
 514             offsetof(zio_link_t, zl_child_node));
 515 
 516         if (vd != NULL)
 517                 zio->io_child_type = ZIO_CHILD_VDEV;
 518         else if (flags & ZIO_FLAG_GANG_CHILD)
 519                 zio->io_child_type = ZIO_CHILD_GANG;
 520         else if (flags & ZIO_FLAG_DDT_CHILD)
 521                 zio->io_child_type = ZIO_CHILD_DDT;
 522         else
 523                 zio->io_child_type = ZIO_CHILD_LOGICAL;
 524 
 525         if (bp != NULL) {
 526                 zio->io_bp = (blkptr_t *)bp;
 527                 zio->io_bp_copy = *bp;
 528                 zio->io_bp_orig = *bp;
 529                 if (type != ZIO_TYPE_WRITE ||
 530                     zio->io_child_type == ZIO_CHILD_DDT)
 531                         zio->io_bp = &zio->io_bp_copy;        /* so caller can free */
 532                 if (zio->io_child_type == ZIO_CHILD_LOGICAL)
 533                         zio->io_logical = zio;
 534                 if (zio->io_child_type > ZIO_CHILD_GANG && BP_IS_GANG(bp))
 535                         pipeline |= ZIO_GANG_STAGES;
 536         }
 537 
 538         zio->io_spa = spa;
 539         zio->io_txg = txg;
 540         zio->io_done = done;
 541         zio->io_private = private;
 542         zio->io_type = type;
 543         zio->io_priority = priority;
 544         zio->io_vd = vd;
 545         zio->io_offset = offset;
 546         zio->io_orig_data = zio->io_data = data;
 547         zio->io_orig_size = zio->io_size = size;
 548         zio->io_orig_flags = zio->io_flags = flags;
 549         zio->io_orig_stage = zio->io_stage = stage;
 550         zio->io_orig_pipeline = zio->io_pipeline = pipeline;
 551 
 552         zio->io_state[ZIO_WAIT_READY] = (stage >= ZIO_STAGE_READY);
 553         zio->io_state[ZIO_WAIT_DONE] = (stage >= ZIO_STAGE_DONE);
 554 
 555         if (zb != NULL)
 556                 zio->io_bookmark = *zb;
 557 
 558         if (pio != NULL) {
 559                 if (zio->io_logical == NULL)
 560                         zio->io_logical = pio->io_logical;
 561                 if (zio->io_child_type == ZIO_CHILD_GANG)
 562                         zio->io_gang_leader = pio->io_gang_leader;
 563                 zio_add_child(pio, zio);
 564         }
 565 
 566         return (zio);
 567 }
 568 
 569 static void
 570 zio_destroy(zio_t *zio)
 571 {
 572         list_destroy(&zio->io_parent_list);
 573         list_destroy(&zio->io_child_list);
 574         mutex_destroy(&zio->io_lock);
 575         cv_destroy(&zio->io_cv);
 576         kmem_cache_free(zio_cache, zio);
 577 }
 578 
 579 zio_t *
 580 zio_null(zio_t *pio, spa_t *spa, vdev_t *vd, zio_done_func_t *done,
 581     void *private, enum zio_flag flags)
 582 {
 583         zio_t *zio;
 584 
 585         zio = zio_create(pio, spa, 0, NULL, NULL, 0, done, private,
 586             ZIO_TYPE_NULL, ZIO_PRIORITY_NOW, flags, vd, 0, NULL,
 587             ZIO_STAGE_OPEN, ZIO_INTERLOCK_PIPELINE);
 588 
 589         return (zio);
 590 }
 591 
 592 zio_t *
 593 zio_root(spa_t *spa, zio_done_func_t *done, void *private, enum zio_flag flags)
 594 {
 595         return (zio_null(NULL, spa, NULL, done, private, flags));
 596 }
 597 
 598 zio_t *
 599 zio_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
 600     void *data, uint64_t size, zio_done_func_t *done, void *private,
 601     zio_priority_t priority, enum zio_flag flags, const zbookmark_phys_t *zb)
 602 {
 603         zio_t *zio;
 604 
 605         zio = zio_create(pio, spa, BP_PHYSICAL_BIRTH(bp), bp,
 606             data, size, done, private,
 607             ZIO_TYPE_READ, priority, flags, NULL, 0, zb,
 608             ZIO_STAGE_OPEN, (flags & ZIO_FLAG_DDT_CHILD) ?
 609             ZIO_DDT_CHILD_READ_PIPELINE : ZIO_READ_PIPELINE);
 610 
 611         return (zio);
 612 }
 613 
 614 zio_t *
 615 zio_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp,
 616     void *data, uint64_t size, const zio_prop_t *zp,
 617     zio_done_func_t *ready, zio_done_func_t *physdone, zio_done_func_t *done,
 618     void *private,
 619     zio_priority_t priority, enum zio_flag flags, const zbookmark_phys_t *zb)
 620 {
 621         zio_t *zio;
 622 
 623         ASSERT(zp->zp_checksum >= ZIO_CHECKSUM_OFF &&
 624             zp->zp_checksum < ZIO_CHECKSUM_FUNCTIONS &&
 625             zp->zp_compress >= ZIO_COMPRESS_OFF &&
 626             zp->zp_compress < ZIO_COMPRESS_FUNCTIONS &&
 627             DMU_OT_IS_VALID(zp->zp_type) &&
 628             zp->zp_level < 32 &&
 629             zp->zp_copies > 0 &&
 630             zp->zp_copies <= spa_max_replication(spa));
 631 
 632         zio = zio_create(pio, spa, txg, bp, data, size, done, private,
 633             ZIO_TYPE_WRITE, priority, flags, NULL, 0, zb,
 634             ZIO_STAGE_OPEN, (flags & ZIO_FLAG_DDT_CHILD) ?
 635             ZIO_DDT_CHILD_WRITE_PIPELINE : ZIO_WRITE_PIPELINE);
 636 
 637         zio->io_ready = ready;
 638         zio->io_physdone = physdone;
 639         zio->io_prop = *zp;
 640 
 641         /*
 642          * Data can be NULL if we are going to call zio_write_override() to
 643          * provide the already-allocated BP.  But we may need the data to
 644          * verify a dedup hit (if requested).  In this case, don't try to
 645          * dedup (just take the already-allocated BP verbatim).
 646          */
 647         if (data == NULL && zio->io_prop.zp_dedup_verify) {
 648                 zio->io_prop.zp_dedup = zio->io_prop.zp_dedup_verify = B_FALSE;
 649         }
 650 
 651         return (zio);
 652 }
 653 
 654 zio_t *
 655 zio_rewrite(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, void *data,
 656     uint64_t size, zio_done_func_t *done, void *private,
 657     zio_priority_t priority, enum zio_flag flags, zbookmark_phys_t *zb)
 658 {
 659         zio_t *zio;
 660 
 661         zio = zio_create(pio, spa, txg, bp, data, size, done, private,
 662             ZIO_TYPE_WRITE, priority, flags, NULL, 0, zb,
 663             ZIO_STAGE_OPEN, ZIO_REWRITE_PIPELINE);
 664 
 665         return (zio);
 666 }
 667 
 668 void
 669 zio_write_override(zio_t *zio, blkptr_t *bp, int copies, boolean_t nopwrite)
 670 {
 671         ASSERT(zio->io_type == ZIO_TYPE_WRITE);
 672         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
 673         ASSERT(zio->io_stage == ZIO_STAGE_OPEN);
 674         ASSERT(zio->io_txg == spa_syncing_txg(zio->io_spa));
 675 
 676         /*
 677          * We must reset the io_prop to match the values that existed
 678          * when the bp was first written by dmu_sync() keeping in mind
 679          * that nopwrite and dedup are mutually exclusive.
 680          */
 681         zio->io_prop.zp_dedup = nopwrite ? B_FALSE : zio->io_prop.zp_dedup;
 682         zio->io_prop.zp_nopwrite = nopwrite;
 683         zio->io_prop.zp_copies = copies;
 684         zio->io_bp_override = bp;
 685 }
 686 
 687 void
 688 zio_free(spa_t *spa, uint64_t txg, const blkptr_t *bp)
 689 {
 690 
 691         /*
 692          * The check for EMBEDDED is a performance optimization.  We
 693          * process the free here (by ignoring it) rather than
 694          * putting it on the list and then processing it in zio_free_sync().
 695          */
 696         if (BP_IS_EMBEDDED(bp))
 697                 return;
 698         metaslab_check_free(spa, bp);
 699 
 700         /*
 701          * Frees that are for the currently-syncing txg, are not going to be
 702          * deferred, and which will not need to do a read (i.e. not GANG or
 703          * DEDUP), can be processed immediately.  Otherwise, put them on the
 704          * in-memory list for later processing.
 705          */
 706         if (BP_IS_GANG(bp) || BP_GET_DEDUP(bp) ||
 707             txg != spa->spa_syncing_txg ||
 708             spa_sync_pass(spa) >= zfs_sync_pass_deferred_free) {
 709                 bplist_append(&spa->spa_free_bplist[txg & TXG_MASK], bp);
 710         } else {
 711                 VERIFY0(zio_wait(zio_free_sync(NULL, spa, txg, bp, 0)));
 712         }
 713 }
 714 
 715 zio_t *
 716 zio_free_sync(zio_t *pio, spa_t *spa, uint64_t txg, const blkptr_t *bp,
 717     enum zio_flag flags)
 718 {
 719         zio_t *zio;
 720         enum zio_stage stage = ZIO_FREE_PIPELINE;
 721 
 722         ASSERT(!BP_IS_HOLE(bp));
 723         ASSERT(spa_syncing_txg(spa) == txg);
 724         ASSERT(spa_sync_pass(spa) < zfs_sync_pass_deferred_free);
 725 
 726         if (BP_IS_EMBEDDED(bp))
 727                 return (zio_null(pio, spa, NULL, NULL, NULL, 0));
 728 
 729         metaslab_check_free(spa, bp);
 730         arc_freed(spa, bp);
 731 
 732         /*
 733          * GANG and DEDUP blocks can induce a read (for the gang block header,
 734          * or the DDT), so issue them asynchronously so that this thread is
 735          * not tied up.
 736          */
 737         if (BP_IS_GANG(bp) || BP_GET_DEDUP(bp))
 738                 stage |= ZIO_STAGE_ISSUE_ASYNC;
 739 
 740         zio = zio_create(pio, spa, txg, bp, NULL, BP_GET_PSIZE(bp),
 741             NULL, NULL, ZIO_TYPE_FREE, ZIO_PRIORITY_NOW, flags,
 742             NULL, 0, NULL, ZIO_STAGE_OPEN, stage);
 743 
 744         return (zio);
 745 }
 746 
 747 zio_t *
 748 zio_claim(zio_t *pio, spa_t *spa, uint64_t txg, const blkptr_t *bp,
 749     zio_done_func_t *done, void *private, enum zio_flag flags)
 750 {
 751         zio_t *zio;
 752 
 753         dprintf_bp(bp, "claiming in txg %llu", txg);
 754 
 755         if (BP_IS_EMBEDDED(bp))
 756                 return (zio_null(pio, spa, NULL, NULL, NULL, 0));
 757 
 758         /*
 759          * A claim is an allocation of a specific block.  Claims are needed
 760          * to support immediate writes in the intent log.  The issue is that
 761          * immediate writes contain committed data, but in a txg that was
 762          * *not* committed.  Upon opening the pool after an unclean shutdown,
 763          * the intent log claims all blocks that contain immediate write data
 764          * so that the SPA knows they're in use.
 765          *
 766          * All claims *must* be resolved in the first txg -- before the SPA
 767          * starts allocating blocks -- so that nothing is allocated twice.
 768          * If txg == 0 we just verify that the block is claimable.
 769          */
 770         ASSERT3U(spa->spa_uberblock.ub_rootbp.blk_birth, <, spa_first_txg(spa));
 771         ASSERT(txg == spa_first_txg(spa) || txg == 0);
 772         ASSERT(!BP_GET_DEDUP(bp) || !spa_writeable(spa));       /* zdb(1M) */
 773 
 774         zio = zio_create(pio, spa, txg, bp, NULL, BP_GET_PSIZE(bp),
 775             done, private, ZIO_TYPE_CLAIM, ZIO_PRIORITY_NOW, flags,
 776             NULL, 0, NULL, ZIO_STAGE_OPEN, ZIO_CLAIM_PIPELINE);
 777 
 778         return (zio);
 779 }
 780 
 781 zio_t *
 782 zio_ioctl(zio_t *pio, spa_t *spa, vdev_t *vd, int cmd,
 783     zio_done_func_t *done, void *private, enum zio_flag flags)
 784 {
 785         zio_t *zio;
 786         int c;
 787 
 788         if (vd->vdev_children == 0) {
 789                 zio = zio_create(pio, spa, 0, NULL, NULL, 0, done, private,
 790                     ZIO_TYPE_IOCTL, ZIO_PRIORITY_NOW, flags, vd, 0, NULL,
 791                     ZIO_STAGE_OPEN, ZIO_IOCTL_PIPELINE);
 792 
 793                 zio->io_cmd = cmd;
 794         } else {
 795                 zio = zio_null(pio, spa, NULL, NULL, NULL, flags);
 796 
 797                 for (c = 0; c < vd->vdev_children; c++)
 798                         zio_nowait(zio_ioctl(zio, spa, vd->vdev_child[c], cmd,
 799                             done, private, flags));
 800         }
 801 
 802         return (zio);
 803 }
 804 
 805 zio_t *
 806 zio_read_phys(zio_t *pio, vdev_t *vd, uint64_t offset, uint64_t size,
 807     void *data, int checksum, zio_done_func_t *done, void *private,
 808     zio_priority_t priority, enum zio_flag flags, boolean_t labels)
 809 {
 810         zio_t *zio;
 811 
 812         ASSERT(vd->vdev_children == 0);
 813         ASSERT(!labels || offset + size <= VDEV_LABEL_START_SIZE ||
 814             offset >= vd->vdev_psize - VDEV_LABEL_END_SIZE);
 815         ASSERT3U(offset + size, <=, vd->vdev_psize);
 816 
 817         zio = zio_create(pio, vd->vdev_spa, 0, NULL, data, size, done, private,
 818             ZIO_TYPE_READ, priority, flags | ZIO_FLAG_PHYSICAL, vd, offset,
 819             NULL, ZIO_STAGE_OPEN, ZIO_READ_PHYS_PIPELINE);
 820 
 821         zio->io_prop.zp_checksum = checksum;
 822 
 823         return (zio);
 824 }
 825 
 826 zio_t *
 827 zio_write_phys(zio_t *pio, vdev_t *vd, uint64_t offset, uint64_t size,
 828     void *data, int checksum, zio_done_func_t *done, void *private,
 829     zio_priority_t priority, enum zio_flag flags, boolean_t labels)
 830 {
 831         zio_t *zio;
 832 
 833         ASSERT(vd->vdev_children == 0);
 834         ASSERT(!labels || offset + size <= VDEV_LABEL_START_SIZE ||
 835             offset >= vd->vdev_psize - VDEV_LABEL_END_SIZE);
 836         ASSERT3U(offset + size, <=, vd->vdev_psize);
 837 
 838         zio = zio_create(pio, vd->vdev_spa, 0, NULL, data, size, done, private,
 839             ZIO_TYPE_WRITE, priority, flags | ZIO_FLAG_PHYSICAL, vd, offset,
 840             NULL, ZIO_STAGE_OPEN, ZIO_WRITE_PHYS_PIPELINE);
 841 
 842         zio->io_prop.zp_checksum = checksum;
 843 
 844         if (zio_checksum_table[checksum].ci_eck) {
 845                 /*
 846                  * zec checksums are necessarily destructive -- they modify
 847                  * the end of the write buffer to hold the verifier/checksum.
 848                  * Therefore, we must make a local copy in case the data is
 849                  * being written to multiple places in parallel.
 850                  */
 851                 void *wbuf = zio_buf_alloc(size);
 852                 bcopy(data, wbuf, size);
 853                 zio_push_transform(zio, wbuf, size, size, NULL);
 854         }
 855 
 856         return (zio);
 857 }
 858 
 859 /*
 860  * Create a child I/O to do some work for us.
 861  */
 862 zio_t *
 863 zio_vdev_child_io(zio_t *pio, blkptr_t *bp, vdev_t *vd, uint64_t offset,
 864         void *data, uint64_t size, int type, zio_priority_t priority,
 865         enum zio_flag flags, zio_done_func_t *done, void *private)
 866 {
 867         enum zio_stage pipeline = ZIO_VDEV_CHILD_PIPELINE;
 868         zio_t *zio;
 869 
 870         ASSERT(vd->vdev_parent ==
 871             (pio->io_vd ? pio->io_vd : pio->io_spa->spa_root_vdev));
 872 
 873         if (type == ZIO_TYPE_READ && bp != NULL) {
 874                 /*
 875                  * If we have the bp, then the child should perform the
 876                  * checksum and the parent need not.  This pushes error
 877                  * detection as close to the leaves as possible and
 878                  * eliminates redundant checksums in the interior nodes.
 879                  */
 880                 pipeline |= ZIO_STAGE_CHECKSUM_VERIFY;
 881                 pio->io_pipeline &= ~ZIO_STAGE_CHECKSUM_VERIFY;
 882         }
 883 
 884         if (vd->vdev_children == 0)
 885                 offset += VDEV_LABEL_START_SIZE;
 886 
 887         flags |= ZIO_VDEV_CHILD_FLAGS(pio) | ZIO_FLAG_DONT_PROPAGATE;
 888 
 889         /*
 890          * If we've decided to do a repair, the write is not speculative --
 891          * even if the original read was.
 892          */
 893         if (flags & ZIO_FLAG_IO_REPAIR)
 894                 flags &= ~ZIO_FLAG_SPECULATIVE;
 895 
 896         zio = zio_create(pio, pio->io_spa, pio->io_txg, bp, data, size,
 897             done, private, type, priority, flags, vd, offset, &pio->io_bookmark,
 898             ZIO_STAGE_VDEV_IO_START >> 1, pipeline);
 899 
 900         zio->io_physdone = pio->io_physdone;
 901         if (vd->vdev_ops->vdev_op_leaf && zio->io_logical != NULL)
 902                 zio->io_logical->io_phys_children++;
 903 
 904         return (zio);
 905 }
 906 
 907 zio_t *
 908 zio_vdev_delegated_io(vdev_t *vd, uint64_t offset, void *data, uint64_t size,
 909         int type, zio_priority_t priority, enum zio_flag flags,
 910         zio_done_func_t *done, void *private)
 911 {
 912         zio_t *zio;
 913 
 914         ASSERT(vd->vdev_ops->vdev_op_leaf);
 915 
 916         zio = zio_create(NULL, vd->vdev_spa, 0, NULL,
 917             data, size, done, private, type, priority,
 918             flags | ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_RETRY | ZIO_FLAG_DELEGATED,
 919             vd, offset, NULL,
 920             ZIO_STAGE_VDEV_IO_START >> 1, ZIO_VDEV_CHILD_PIPELINE);
 921 
 922         return (zio);
 923 }
 924 
 925 void
 926 zio_flush(zio_t *zio, vdev_t *vd)
 927 {
 928         zio_nowait(zio_ioctl(zio, zio->io_spa, vd, DKIOCFLUSHWRITECACHE,
 929             NULL, NULL,
 930             ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY));
 931 }
 932 
 933 void
 934 zio_shrink(zio_t *zio, uint64_t size)
 935 {
 936         ASSERT(zio->io_executor == NULL);
 937         ASSERT(zio->io_orig_size == zio->io_size);
 938         ASSERT(size <= zio->io_size);
 939 
 940         /*
 941          * We don't shrink for raidz because of problems with the
 942          * reconstruction when reading back less than the block size.
 943          * Note, BP_IS_RAIDZ() assumes no compression.
 944          */
 945         ASSERT(BP_GET_COMPRESS(zio->io_bp) == ZIO_COMPRESS_OFF);
 946         if (!BP_IS_RAIDZ(zio->io_bp))
 947                 zio->io_orig_size = zio->io_size = size;
 948 }
 949 
 950 /*
 951  * ==========================================================================
 952  * Prepare to read and write logical blocks
 953  * ==========================================================================
 954  */
 955 
 956 static int
 957 zio_read_bp_init(zio_t *zio)
 958 {
 959         blkptr_t *bp = zio->io_bp;
 960 
 961         if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF &&
 962             zio->io_child_type == ZIO_CHILD_LOGICAL &&
 963             !(zio->io_flags & ZIO_FLAG_RAW)) {
 964                 uint64_t psize =
 965                     BP_IS_EMBEDDED(bp) ? BPE_GET_PSIZE(bp) : BP_GET_PSIZE(bp);
 966                 void *cbuf = zio_buf_alloc(psize);
 967 
 968                 zio_push_transform(zio, cbuf, psize, psize, zio_decompress);
 969         }
 970 
 971         if (BP_IS_EMBEDDED(bp) && BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA) {
 972                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
 973                 decode_embedded_bp_compressed(bp, zio->io_data);
 974         } else {
 975                 ASSERT(!BP_IS_EMBEDDED(bp));
 976         }
 977 
 978         if (!DMU_OT_IS_METADATA(BP_GET_TYPE(bp)) && BP_GET_LEVEL(bp) == 0)
 979                 zio->io_flags |= ZIO_FLAG_DONT_CACHE;
 980 
 981         if (BP_GET_TYPE(bp) == DMU_OT_DDT_ZAP)
 982                 zio->io_flags |= ZIO_FLAG_DONT_CACHE;
 983 
 984         if (BP_GET_DEDUP(bp) && zio->io_child_type == ZIO_CHILD_LOGICAL)
 985                 zio->io_pipeline = ZIO_DDT_READ_PIPELINE;
 986 
 987         return (ZIO_PIPELINE_CONTINUE);
 988 }
 989 
 990 static int
 991 zio_write_bp_init(zio_t *zio)
 992 {
 993         spa_t *spa = zio->io_spa;
 994         zio_prop_t *zp = &zio->io_prop;
 995         enum zio_compress compress = zp->zp_compress;
 996         blkptr_t *bp = zio->io_bp;
 997         uint64_t lsize = zio->io_size;
 998         uint64_t psize = lsize;
 999         int pass = 1;
1000 
1001         /*
1002          * If our children haven't all reached the ready stage,
1003          * wait for them and then repeat this pipeline stage.
1004          */
1005         if (zio_wait_for_children(zio, ZIO_CHILD_GANG, ZIO_WAIT_READY) ||
1006             zio_wait_for_children(zio, ZIO_CHILD_LOGICAL, ZIO_WAIT_READY))
1007                 return (ZIO_PIPELINE_STOP);
1008 
1009         if (!IO_IS_ALLOCATING(zio))
1010                 return (ZIO_PIPELINE_CONTINUE);
1011 
1012         ASSERT(zio->io_child_type != ZIO_CHILD_DDT);
1013 
1014         if (zio->io_bp_override) {
1015                 ASSERT(bp->blk_birth != zio->io_txg);
1016                 ASSERT(BP_GET_DEDUP(zio->io_bp_override) == 0);
1017 
1018                 *bp = *zio->io_bp_override;
1019                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1020 
1021                 if (BP_IS_EMBEDDED(bp))
1022                         return (ZIO_PIPELINE_CONTINUE);
1023 
1024                 /*
1025                  * If we've been overridden and nopwrite is set then
1026                  * set the flag accordingly to indicate that a nopwrite
1027                  * has already occurred.
1028                  */
1029                 if (!BP_IS_HOLE(bp) && zp->zp_nopwrite) {
1030                         ASSERT(!zp->zp_dedup);
1031                         zio->io_flags |= ZIO_FLAG_NOPWRITE;
1032                         return (ZIO_PIPELINE_CONTINUE);
1033                 }
1034 
1035                 ASSERT(!zp->zp_nopwrite);
1036 
1037                 if (BP_IS_HOLE(bp) || !zp->zp_dedup)
1038                         return (ZIO_PIPELINE_CONTINUE);
1039 
1040                 ASSERT(zio_checksum_table[zp->zp_checksum].ci_dedup ||
1041                     zp->zp_dedup_verify);
1042 
1043                 if (BP_GET_CHECKSUM(bp) == zp->zp_checksum) {
1044                         BP_SET_DEDUP(bp, 1);
1045                         zio->io_pipeline |= ZIO_STAGE_DDT_WRITE;
1046                         return (ZIO_PIPELINE_CONTINUE);
1047                 }
1048                 zio->io_bp_override = NULL;
1049                 BP_ZERO(bp);
1050         }
1051 
1052         if (!BP_IS_HOLE(bp) && bp->blk_birth == zio->io_txg) {
1053                 /*
1054                  * We're rewriting an existing block, which means we're
1055                  * working on behalf of spa_sync().  For spa_sync() to
1056                  * converge, it must eventually be the case that we don't
1057                  * have to allocate new blocks.  But compression changes
1058                  * the blocksize, which forces a reallocate, and makes
1059                  * convergence take longer.  Therefore, after the first
1060                  * few passes, stop compressing to ensure convergence.
1061                  */
1062                 pass = spa_sync_pass(spa);
1063 
1064                 ASSERT(zio->io_txg == spa_syncing_txg(spa));
1065                 ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
1066                 ASSERT(!BP_GET_DEDUP(bp));
1067 
1068                 if (pass >= zfs_sync_pass_dont_compress)
1069                         compress = ZIO_COMPRESS_OFF;
1070 
1071                 /* Make sure someone doesn't change their mind on overwrites */
1072                 ASSERT(BP_IS_EMBEDDED(bp) || MIN(zp->zp_copies + BP_IS_GANG(bp),
1073                     spa_max_replication(spa)) == BP_GET_NDVAS(bp));
1074         }
1075 
1076         if (compress != ZIO_COMPRESS_OFF) {
1077                 void *cbuf = zio_buf_alloc(lsize);
1078                 psize = zio_compress_data(compress, zio->io_data, cbuf, lsize);
1079                 if (psize == 0 || psize == lsize) {
1080                         compress = ZIO_COMPRESS_OFF;
1081                         zio_buf_free(cbuf, lsize);
1082                 } else if (!zp->zp_dedup && psize <= BPE_PAYLOAD_SIZE &&
1083                     zp->zp_level == 0 && !DMU_OT_HAS_FILL(zp->zp_type) &&
1084                     spa_feature_is_enabled(spa, SPA_FEATURE_EMBEDDED_DATA)) {
1085                         encode_embedded_bp_compressed(bp,
1086                             cbuf, compress, lsize, psize);
1087                         BPE_SET_ETYPE(bp, BP_EMBEDDED_TYPE_DATA);
1088                         BP_SET_TYPE(bp, zio->io_prop.zp_type);
1089                         BP_SET_LEVEL(bp, zio->io_prop.zp_level);
1090                         zio_buf_free(cbuf, lsize);
1091                         bp->blk_birth = zio->io_txg;
1092                         zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1093                         ASSERT(spa_feature_is_active(spa,
1094                             SPA_FEATURE_EMBEDDED_DATA));
1095                         return (ZIO_PIPELINE_CONTINUE);
1096                 } else {
1097                         /*
1098                          * Round up compressed size to MINBLOCKSIZE and
1099                          * zero the tail.
1100                          */
1101                         size_t rounded =
1102                             P2ROUNDUP(psize, (size_t)SPA_MINBLOCKSIZE);
1103                         if (rounded > psize) {
1104                                 bzero((char *)cbuf + psize, rounded - psize);
1105                                 psize = rounded;
1106                         }
1107                         if (psize == lsize) {
1108                                 compress = ZIO_COMPRESS_OFF;
1109                                 zio_buf_free(cbuf, lsize);
1110                         } else {
1111                                 zio_push_transform(zio, cbuf,
1112                                     psize, lsize, NULL);
1113                         }
1114                 }
1115         }
1116 
1117         /*
1118          * The final pass of spa_sync() must be all rewrites, but the first
1119          * few passes offer a trade-off: allocating blocks defers convergence,
1120          * but newly allocated blocks are sequential, so they can be written
1121          * to disk faster.  Therefore, we allow the first few passes of
1122          * spa_sync() to allocate new blocks, but force rewrites after that.
1123          * There should only be a handful of blocks after pass 1 in any case.
1124          */
1125         if (!BP_IS_HOLE(bp) && bp->blk_birth == zio->io_txg &&
1126             BP_GET_PSIZE(bp) == psize &&
1127             pass >= zfs_sync_pass_rewrite) {
1128                 ASSERT(psize != 0);
1129                 enum zio_stage gang_stages = zio->io_pipeline & ZIO_GANG_STAGES;
1130                 zio->io_pipeline = ZIO_REWRITE_PIPELINE | gang_stages;
1131                 zio->io_flags |= ZIO_FLAG_IO_REWRITE;
1132         } else {
1133                 BP_ZERO(bp);
1134                 zio->io_pipeline = ZIO_WRITE_PIPELINE;
1135         }
1136 
1137         if (psize == 0) {
1138                 if (zio->io_bp_orig.blk_birth != 0 &&
1139                     spa_feature_is_active(spa, SPA_FEATURE_HOLE_BIRTH)) {
1140                         BP_SET_LSIZE(bp, lsize);
1141                         BP_SET_TYPE(bp, zp->zp_type);
1142                         BP_SET_LEVEL(bp, zp->zp_level);
1143                         BP_SET_BIRTH(bp, zio->io_txg, 0);
1144                 }
1145                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1146         } else {
1147                 ASSERT(zp->zp_checksum != ZIO_CHECKSUM_GANG_HEADER);
1148                 BP_SET_LSIZE(bp, lsize);
1149                 BP_SET_TYPE(bp, zp->zp_type);
1150                 BP_SET_LEVEL(bp, zp->zp_level);
1151                 BP_SET_PSIZE(bp, psize);
1152                 BP_SET_COMPRESS(bp, compress);
1153                 BP_SET_CHECKSUM(bp, zp->zp_checksum);
1154                 BP_SET_DEDUP(bp, zp->zp_dedup);
1155                 BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
1156                 if (zp->zp_dedup) {
1157                         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
1158                         ASSERT(!(zio->io_flags & ZIO_FLAG_IO_REWRITE));
1159                         zio->io_pipeline = ZIO_DDT_WRITE_PIPELINE;
1160                 }
1161                 if (zp->zp_nopwrite) {
1162                         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
1163                         ASSERT(!(zio->io_flags & ZIO_FLAG_IO_REWRITE));
1164                         zio->io_pipeline |= ZIO_STAGE_NOP_WRITE;
1165                 }
1166         }
1167 
1168         return (ZIO_PIPELINE_CONTINUE);
1169 }
1170 
1171 static int
1172 zio_free_bp_init(zio_t *zio)
1173 {
1174         blkptr_t *bp = zio->io_bp;
1175 
1176         if (zio->io_child_type == ZIO_CHILD_LOGICAL) {
1177                 if (BP_GET_DEDUP(bp))
1178                         zio->io_pipeline = ZIO_DDT_FREE_PIPELINE;
1179         }
1180 
1181         return (ZIO_PIPELINE_CONTINUE);
1182 }
1183 
1184 /*
1185  * ==========================================================================
1186  * Execute the I/O pipeline
1187  * ==========================================================================
1188  */
1189 
1190 static void
1191 zio_taskq_dispatch(zio_t *zio, zio_taskq_type_t q, boolean_t cutinline)
1192 {
1193         spa_t *spa = zio->io_spa;
1194         zio_type_t t = zio->io_type;
1195         int flags = (cutinline ? TQ_FRONT : 0);
1196 
1197         /*
1198          * If we're a config writer or a probe, the normal issue and
1199          * interrupt threads may all be blocked waiting for the config lock.
1200          * In this case, select the otherwise-unused taskq for ZIO_TYPE_NULL.
1201          */
1202         if (zio->io_flags & (ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_PROBE))
1203                 t = ZIO_TYPE_NULL;
1204 
1205         /*
1206          * A similar issue exists for the L2ARC write thread until L2ARC 2.0.
1207          */
1208         if (t == ZIO_TYPE_WRITE && zio->io_vd && zio->io_vd->vdev_aux)
1209                 t = ZIO_TYPE_NULL;
1210 
1211         /*
1212          * If this is a high priority I/O, then use the high priority taskq if
1213          * available.
1214          */
1215         if (zio->io_priority == ZIO_PRIORITY_NOW &&
1216             spa->spa_zio_taskq[t][q + 1].stqs_count != 0)
1217                 q++;
1218 
1219         ASSERT3U(q, <, ZIO_TASKQ_TYPES);
1220 
1221         /*
1222          * NB: We are assuming that the zio can only be dispatched
1223          * to a single taskq at a time.  It would be a grievous error
1224          * to dispatch the zio to another taskq at the same time.
1225          */
1226         ASSERT(zio->io_tqent.tqent_next == NULL);
1227         spa_taskq_dispatch_ent(spa, t, q, (task_func_t *)zio_execute, zio,
1228             flags, &zio->io_tqent);
1229 }
1230 
1231 static boolean_t
1232 zio_taskq_member(zio_t *zio, zio_taskq_type_t q)
1233 {
1234         kthread_t *executor = zio->io_executor;
1235         spa_t *spa = zio->io_spa;
1236 
1237         for (zio_type_t t = 0; t < ZIO_TYPES; t++) {
1238                 spa_taskqs_t *tqs = &spa->spa_zio_taskq[t][q];
1239                 uint_t i;
1240                 for (i = 0; i < tqs->stqs_count; i++) {
1241                         if (taskq_member(tqs->stqs_taskq[i], executor))
1242                                 return (B_TRUE);
1243                 }
1244         }
1245 
1246         return (B_FALSE);
1247 }
1248 
1249 static int
1250 zio_issue_async(zio_t *zio)
1251 {
1252         zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE, B_FALSE);
1253 
1254         return (ZIO_PIPELINE_STOP);
1255 }
1256 
1257 void
1258 zio_interrupt(zio_t *zio)
1259 {
1260         zio_taskq_dispatch(zio, ZIO_TASKQ_INTERRUPT, B_FALSE);
1261 }
1262 
1263 /*
1264  * Execute the I/O pipeline until one of the following occurs:
1265  *
1266  *      (1) the I/O completes
1267  *      (2) the pipeline stalls waiting for dependent child I/Os
1268  *      (3) the I/O issues, so we're waiting for an I/O completion interrupt
1269  *      (4) the I/O is delegated by vdev-level caching or aggregation
1270  *      (5) the I/O is deferred due to vdev-level queueing
1271  *      (6) the I/O is handed off to another thread.
1272  *
1273  * In all cases, the pipeline stops whenever there's no CPU work; it never
1274  * burns a thread in cv_wait().
1275  *
1276  * There's no locking on io_stage because there's no legitimate way
1277  * for multiple threads to be attempting to process the same I/O.
1278  */
1279 static zio_pipe_stage_t *zio_pipeline[];
1280 
1281 void
1282 zio_execute(zio_t *zio)
1283 {
1284         zio->io_executor = curthread;
1285 
1286         while (zio->io_stage < ZIO_STAGE_DONE) {
1287                 enum zio_stage pipeline = zio->io_pipeline;
1288                 enum zio_stage stage = zio->io_stage;
1289                 int rv;
1290 
1291                 ASSERT(!MUTEX_HELD(&zio->io_lock));
1292                 ASSERT(ISP2(stage));
1293                 ASSERT(zio->io_stall == NULL);
1294 
1295                 do {
1296                         stage <<= 1;
1297                 } while ((stage & pipeline) == 0);
1298 
1299                 ASSERT(stage <= ZIO_STAGE_DONE);
1300 
1301                 /*
1302                  * If we are in interrupt context and this pipeline stage
1303                  * will grab a config lock that is held across I/O,
1304                  * or may wait for an I/O that needs an interrupt thread
1305                  * to complete, issue async to avoid deadlock.
1306                  *
1307                  * For VDEV_IO_START, we cut in line so that the io will
1308                  * be sent to disk promptly.
1309                  */
1310                 if ((stage & ZIO_BLOCKING_STAGES) && zio->io_vd == NULL &&
1311                     zio_taskq_member(zio, ZIO_TASKQ_INTERRUPT)) {
1312                         boolean_t cut = (stage == ZIO_STAGE_VDEV_IO_START) ?
1313                             zio_requeue_io_start_cut_in_line : B_FALSE;
1314                         zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE, cut);
1315                         return;
1316                 }
1317 
1318                 zio->io_stage = stage;
1319                 rv = zio_pipeline[highbit64(stage) - 1](zio);
1320 
1321                 if (rv == ZIO_PIPELINE_STOP)
1322                         return;
1323 
1324                 ASSERT(rv == ZIO_PIPELINE_CONTINUE);
1325         }
1326 }
1327 
1328 /*
1329  * ==========================================================================
1330  * Initiate I/O, either sync or async
1331  * ==========================================================================
1332  */
1333 int
1334 zio_wait(zio_t *zio)
1335 {
1336         int error;
1337 
1338         ASSERT(zio->io_stage == ZIO_STAGE_OPEN);
1339         ASSERT(zio->io_executor == NULL);
1340 
1341         zio->io_waiter = curthread;
1342 
1343         zio_execute(zio);
1344 
1345         mutex_enter(&zio->io_lock);
1346         while (zio->io_executor != NULL)
1347                 cv_wait(&zio->io_cv, &zio->io_lock);
1348         mutex_exit(&zio->io_lock);
1349 
1350         error = zio->io_error;
1351         zio_destroy(zio);
1352 
1353         return (error);
1354 }
1355 
1356 void
1357 zio_nowait(zio_t *zio)
1358 {
1359         ASSERT(zio->io_executor == NULL);
1360 
1361         if (zio->io_child_type == ZIO_CHILD_LOGICAL &&
1362             zio_unique_parent(zio) == NULL) {
1363                 /*
1364                  * This is a logical async I/O with no parent to wait for it.
1365                  * We add it to the spa_async_root_zio "Godfather" I/O which
1366                  * will ensure they complete prior to unloading the pool.
1367                  */
1368                 spa_t *spa = zio->io_spa;
1369 
1370                 zio_add_child(spa->spa_async_zio_root[CPU_SEQID], zio);
1371         }
1372 
1373         zio_execute(zio);
1374 }
1375 
1376 /*
1377  * ==========================================================================
1378  * Reexecute or suspend/resume failed I/O
1379  * ==========================================================================
1380  */
1381 
1382 static void
1383 zio_reexecute(zio_t *pio)
1384 {
1385         zio_t *cio, *cio_next;
1386 
1387         ASSERT(pio->io_child_type == ZIO_CHILD_LOGICAL);
1388         ASSERT(pio->io_orig_stage == ZIO_STAGE_OPEN);
1389         ASSERT(pio->io_gang_leader == NULL);
1390         ASSERT(pio->io_gang_tree == NULL);
1391 
1392         pio->io_flags = pio->io_orig_flags;
1393         pio->io_stage = pio->io_orig_stage;
1394         pio->io_pipeline = pio->io_orig_pipeline;
1395         pio->io_reexecute = 0;
1396         pio->io_flags |= ZIO_FLAG_REEXECUTED;
1397         pio->io_error = 0;
1398         for (int w = 0; w < ZIO_WAIT_TYPES; w++)
1399                 pio->io_state[w] = 0;
1400         for (int c = 0; c < ZIO_CHILD_TYPES; c++)
1401                 pio->io_child_error[c] = 0;
1402 
1403         if (IO_IS_ALLOCATING(pio))
1404                 BP_ZERO(pio->io_bp);
1405 
1406         /*
1407          * As we reexecute pio's children, new children could be created.
1408          * New children go to the head of pio's io_child_list, however,
1409          * so we will (correctly) not reexecute them.  The key is that
1410          * the remainder of pio's io_child_list, from 'cio_next' onward,
1411          * cannot be affected by any side effects of reexecuting 'cio'.
1412          */
1413         for (cio = zio_walk_children(pio); cio != NULL; cio = cio_next) {
1414                 cio_next = zio_walk_children(pio);
1415                 mutex_enter(&pio->io_lock);
1416                 for (int w = 0; w < ZIO_WAIT_TYPES; w++)
1417                         pio->io_children[cio->io_child_type][w]++;
1418                 mutex_exit(&pio->io_lock);
1419                 zio_reexecute(cio);
1420         }
1421 
1422         /*
1423          * Now that all children have been reexecuted, execute the parent.
1424          * We don't reexecute "The Godfather" I/O here as it's the
1425          * responsibility of the caller to wait on him.
1426          */
1427         if (!(pio->io_flags & ZIO_FLAG_GODFATHER))
1428                 zio_execute(pio);
1429 }
1430 
1431 void
1432 zio_suspend(spa_t *spa, zio_t *zio)
1433 {
1434         if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_PANIC)
1435                 fm_panic("Pool '%s' has encountered an uncorrectable I/O "
1436                     "failure and the failure mode property for this pool "
1437                     "is set to panic.", spa_name(spa));
1438 
1439         zfs_ereport_post(FM_EREPORT_ZFS_IO_FAILURE, spa, NULL, NULL, 0, 0);
1440 
1441         mutex_enter(&spa->spa_suspend_lock);
1442 
1443         if (spa->spa_suspend_zio_root == NULL)
1444                 spa->spa_suspend_zio_root = zio_root(spa, NULL, NULL,
1445                     ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE |
1446                     ZIO_FLAG_GODFATHER);
1447 
1448         spa->spa_suspended = B_TRUE;
1449 
1450         if (zio != NULL) {
1451                 ASSERT(!(zio->io_flags & ZIO_FLAG_GODFATHER));
1452                 ASSERT(zio != spa->spa_suspend_zio_root);
1453                 ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
1454                 ASSERT(zio_unique_parent(zio) == NULL);
1455                 ASSERT(zio->io_stage == ZIO_STAGE_DONE);
1456                 zio_add_child(spa->spa_suspend_zio_root, zio);
1457         }
1458 
1459         mutex_exit(&spa->spa_suspend_lock);
1460 }
1461 
1462 int
1463 zio_resume(spa_t *spa)
1464 {
1465         zio_t *pio;
1466 
1467         /*
1468          * Reexecute all previously suspended i/o.
1469          */
1470         mutex_enter(&spa->spa_suspend_lock);
1471         spa->spa_suspended = B_FALSE;
1472         cv_broadcast(&spa->spa_suspend_cv);
1473         pio = spa->spa_suspend_zio_root;
1474         spa->spa_suspend_zio_root = NULL;
1475         mutex_exit(&spa->spa_suspend_lock);
1476 
1477         if (pio == NULL)
1478                 return (0);
1479 
1480         zio_reexecute(pio);
1481         return (zio_wait(pio));
1482 }
1483 
1484 void
1485 zio_resume_wait(spa_t *spa)
1486 {
1487         mutex_enter(&spa->spa_suspend_lock);
1488         while (spa_suspended(spa))
1489                 cv_wait(&spa->spa_suspend_cv, &spa->spa_suspend_lock);
1490         mutex_exit(&spa->spa_suspend_lock);
1491 }
1492 
1493 /*
1494  * ==========================================================================
1495  * Gang blocks.
1496  *
1497  * A gang block is a collection of small blocks that looks to the DMU
1498  * like one large block.  When zio_dva_allocate() cannot find a block
1499  * of the requested size, due to either severe fragmentation or the pool
1500  * being nearly full, it calls zio_write_gang_block() to construct the
1501  * block from smaller fragments.
1502  *
1503  * A gang block consists of a gang header (zio_gbh_phys_t) and up to
1504  * three (SPA_GBH_NBLKPTRS) gang members.  The gang header is just like
1505  * an indirect block: it's an array of block pointers.  It consumes
1506  * only one sector and hence is allocatable regardless of fragmentation.
1507  * The gang header's bps point to its gang members, which hold the data.
1508  *
1509  * Gang blocks are self-checksumming, using the bp's <vdev, offset, txg>
1510  * as the verifier to ensure uniqueness of the SHA256 checksum.
1511  * Critically, the gang block bp's blk_cksum is the checksum of the data,
1512  * not the gang header.  This ensures that data block signatures (needed for
1513  * deduplication) are independent of how the block is physically stored.
1514  *
1515  * Gang blocks can be nested: a gang member may itself be a gang block.
1516  * Thus every gang block is a tree in which root and all interior nodes are
1517  * gang headers, and the leaves are normal blocks that contain user data.
1518  * The root of the gang tree is called the gang leader.
1519  *
1520  * To perform any operation (read, rewrite, free, claim) on a gang block,
1521  * zio_gang_assemble() first assembles the gang tree (minus data leaves)
1522  * in the io_gang_tree field of the original logical i/o by recursively
1523  * reading the gang leader and all gang headers below it.  This yields
1524  * an in-core tree containing the contents of every gang header and the
1525  * bps for every constituent of the gang block.
1526  *
1527  * With the gang tree now assembled, zio_gang_issue() just walks the gang tree
1528  * and invokes a callback on each bp.  To free a gang block, zio_gang_issue()
1529  * calls zio_free_gang() -- a trivial wrapper around zio_free() -- for each bp.
1530  * zio_claim_gang() provides a similarly trivial wrapper for zio_claim().
1531  * zio_read_gang() is a wrapper around zio_read() that omits reading gang
1532  * headers, since we already have those in io_gang_tree.  zio_rewrite_gang()
1533  * performs a zio_rewrite() of the data or, for gang headers, a zio_rewrite()
1534  * of the gang header plus zio_checksum_compute() of the data to update the
1535  * gang header's blk_cksum as described above.
1536  *
1537  * The two-phase assemble/issue model solves the problem of partial failure --
1538  * what if you'd freed part of a gang block but then couldn't read the
1539  * gang header for another part?  Assembling the entire gang tree first
1540  * ensures that all the necessary gang header I/O has succeeded before
1541  * starting the actual work of free, claim, or write.  Once the gang tree
1542  * is assembled, free and claim are in-memory operations that cannot fail.
1543  *
1544  * In the event that a gang write fails, zio_dva_unallocate() walks the
1545  * gang tree to immediately free (i.e. insert back into the space map)
1546  * everything we've allocated.  This ensures that we don't get ENOSPC
1547  * errors during repeated suspend/resume cycles due to a flaky device.
1548  *
1549  * Gang rewrites only happen during sync-to-convergence.  If we can't assemble
1550  * the gang tree, we won't modify the block, so we can safely defer the free
1551  * (knowing that the block is still intact).  If we *can* assemble the gang
1552  * tree, then even if some of the rewrites fail, zio_dva_unallocate() will free
1553  * each constituent bp and we can allocate a new block on the next sync pass.
1554  *
1555  * In all cases, the gang tree allows complete recovery from partial failure.
1556  * ==========================================================================
1557  */
1558 
1559 static zio_t *
1560 zio_read_gang(zio_t *pio, blkptr_t *bp, zio_gang_node_t *gn, void *data)
1561 {
1562         if (gn != NULL)
1563                 return (pio);
1564 
1565         return (zio_read(pio, pio->io_spa, bp, data, BP_GET_PSIZE(bp),
1566             NULL, NULL, pio->io_priority, ZIO_GANG_CHILD_FLAGS(pio),
1567             &pio->io_bookmark));
1568 }
1569 
1570 zio_t *
1571 zio_rewrite_gang(zio_t *pio, blkptr_t *bp, zio_gang_node_t *gn, void *data)
1572 {
1573         zio_t *zio;
1574 
1575         if (gn != NULL) {
1576                 zio = zio_rewrite(pio, pio->io_spa, pio->io_txg, bp,
1577                     gn->gn_gbh, SPA_GANGBLOCKSIZE, NULL, NULL, pio->io_priority,
1578                     ZIO_GANG_CHILD_FLAGS(pio), &pio->io_bookmark);
1579                 /*
1580                  * As we rewrite each gang header, the pipeline will compute
1581                  * a new gang block header checksum for it; but no one will
1582                  * compute a new data checksum, so we do that here.  The one
1583                  * exception is the gang leader: the pipeline already computed
1584                  * its data checksum because that stage precedes gang assembly.
1585                  * (Presently, nothing actually uses interior data checksums;
1586                  * this is just good hygiene.)
1587                  */
1588                 if (gn != pio->io_gang_leader->io_gang_tree) {
1589                         zio_checksum_compute(zio, BP_GET_CHECKSUM(bp),
1590                             data, BP_GET_PSIZE(bp));
1591                 }
1592                 /*
1593                  * If we are here to damage data for testing purposes,
1594                  * leave the GBH alone so that we can detect the damage.
1595                  */
1596                 if (pio->io_gang_leader->io_flags & ZIO_FLAG_INDUCE_DAMAGE)
1597                         zio->io_pipeline &= ~ZIO_VDEV_IO_STAGES;
1598         } else {
1599                 zio = zio_rewrite(pio, pio->io_spa, pio->io_txg, bp,
1600                     data, BP_GET_PSIZE(bp), NULL, NULL, pio->io_priority,
1601                     ZIO_GANG_CHILD_FLAGS(pio), &pio->io_bookmark);
1602         }
1603 
1604         return (zio);
1605 }
1606 
1607 /* ARGSUSED */
1608 zio_t *
1609 zio_free_gang(zio_t *pio, blkptr_t *bp, zio_gang_node_t *gn, void *data)
1610 {
1611         return (zio_free_sync(pio, pio->io_spa, pio->io_txg, bp,
1612             ZIO_GANG_CHILD_FLAGS(pio)));
1613 }
1614 
1615 /* ARGSUSED */
1616 zio_t *
1617 zio_claim_gang(zio_t *pio, blkptr_t *bp, zio_gang_node_t *gn, void *data)
1618 {
1619         return (zio_claim(pio, pio->io_spa, pio->io_txg, bp,
1620             NULL, NULL, ZIO_GANG_CHILD_FLAGS(pio)));
1621 }
1622 
1623 static zio_gang_issue_func_t *zio_gang_issue_func[ZIO_TYPES] = {
1624         NULL,
1625         zio_read_gang,
1626         zio_rewrite_gang,
1627         zio_free_gang,
1628         zio_claim_gang,
1629         NULL
1630 };
1631 
1632 static void zio_gang_tree_assemble_done(zio_t *zio);
1633 
1634 static zio_gang_node_t *
1635 zio_gang_node_alloc(zio_gang_node_t **gnpp)
1636 {
1637         zio_gang_node_t *gn;
1638 
1639         ASSERT(*gnpp == NULL);
1640 
1641         gn = kmem_zalloc(sizeof (*gn), KM_SLEEP);
1642         gn->gn_gbh = zio_buf_alloc(SPA_GANGBLOCKSIZE);
1643         *gnpp = gn;
1644 
1645         return (gn);
1646 }
1647 
1648 static void
1649 zio_gang_node_free(zio_gang_node_t **gnpp)
1650 {
1651         zio_gang_node_t *gn = *gnpp;
1652 
1653         for (int g = 0; g < SPA_GBH_NBLKPTRS; g++)
1654                 ASSERT(gn->gn_child[g] == NULL);
1655 
1656         zio_buf_free(gn->gn_gbh, SPA_GANGBLOCKSIZE);
1657         kmem_free(gn, sizeof (*gn));
1658         *gnpp = NULL;
1659 }
1660 
1661 static void
1662 zio_gang_tree_free(zio_gang_node_t **gnpp)
1663 {
1664         zio_gang_node_t *gn = *gnpp;
1665 
1666         if (gn == NULL)
1667                 return;
1668 
1669         for (int g = 0; g < SPA_GBH_NBLKPTRS; g++)
1670                 zio_gang_tree_free(&gn->gn_child[g]);
1671 
1672         zio_gang_node_free(gnpp);
1673 }
1674 
1675 static void
1676 zio_gang_tree_assemble(zio_t *gio, blkptr_t *bp, zio_gang_node_t **gnpp)
1677 {
1678         zio_gang_node_t *gn = zio_gang_node_alloc(gnpp);
1679 
1680         ASSERT(gio->io_gang_leader == gio);
1681         ASSERT(BP_IS_GANG(bp));
1682 
1683         zio_nowait(zio_read(gio, gio->io_spa, bp, gn->gn_gbh,
1684             SPA_GANGBLOCKSIZE, zio_gang_tree_assemble_done, gn,
1685             gio->io_priority, ZIO_GANG_CHILD_FLAGS(gio), &gio->io_bookmark));
1686 }
1687 
1688 static void
1689 zio_gang_tree_assemble_done(zio_t *zio)
1690 {
1691         zio_t *gio = zio->io_gang_leader;
1692         zio_gang_node_t *gn = zio->io_private;
1693         blkptr_t *bp = zio->io_bp;
1694 
1695         ASSERT(gio == zio_unique_parent(zio));
1696         ASSERT(zio->io_child_count == 0);
1697 
1698         if (zio->io_error)
1699                 return;
1700 
1701         if (BP_SHOULD_BYTESWAP(bp))
1702                 byteswap_uint64_array(zio->io_data, zio->io_size);
1703 
1704         ASSERT(zio->io_data == gn->gn_gbh);
1705         ASSERT(zio->io_size == SPA_GANGBLOCKSIZE);
1706         ASSERT(gn->gn_gbh->zg_tail.zec_magic == ZEC_MAGIC);
1707 
1708         for (int g = 0; g < SPA_GBH_NBLKPTRS; g++) {
1709                 blkptr_t *gbp = &gn->gn_gbh->zg_blkptr[g];
1710                 if (!BP_IS_GANG(gbp))
1711                         continue;
1712                 zio_gang_tree_assemble(gio, gbp, &gn->gn_child[g]);
1713         }
1714 }
1715 
1716 static void
1717 zio_gang_tree_issue(zio_t *pio, zio_gang_node_t *gn, blkptr_t *bp, void *data)
1718 {
1719         zio_t *gio = pio->io_gang_leader;
1720         zio_t *zio;
1721 
1722         ASSERT(BP_IS_GANG(bp) == !!gn);
1723         ASSERT(BP_GET_CHECKSUM(bp) == BP_GET_CHECKSUM(gio->io_bp));
1724         ASSERT(BP_GET_LSIZE(bp) == BP_GET_PSIZE(bp) || gn == gio->io_gang_tree);
1725 
1726         /*
1727          * If you're a gang header, your data is in gn->gn_gbh.
1728          * If you're a gang member, your data is in 'data' and gn == NULL.
1729          */
1730         zio = zio_gang_issue_func[gio->io_type](pio, bp, gn, data);
1731 
1732         if (gn != NULL) {
1733                 ASSERT(gn->gn_gbh->zg_tail.zec_magic == ZEC_MAGIC);
1734 
1735                 for (int g = 0; g < SPA_GBH_NBLKPTRS; g++) {
1736                         blkptr_t *gbp = &gn->gn_gbh->zg_blkptr[g];
1737                         if (BP_IS_HOLE(gbp))
1738                                 continue;
1739                         zio_gang_tree_issue(zio, gn->gn_child[g], gbp, data);
1740                         data = (char *)data + BP_GET_PSIZE(gbp);
1741                 }
1742         }
1743 
1744         if (gn == gio->io_gang_tree)
1745                 ASSERT3P((char *)gio->io_data + gio->io_size, ==, data);
1746 
1747         if (zio != pio)
1748                 zio_nowait(zio);
1749 }
1750 
1751 static int
1752 zio_gang_assemble(zio_t *zio)
1753 {
1754         blkptr_t *bp = zio->io_bp;
1755 
1756         ASSERT(BP_IS_GANG(bp) && zio->io_gang_leader == NULL);
1757         ASSERT(zio->io_child_type > ZIO_CHILD_GANG);
1758 
1759         zio->io_gang_leader = zio;
1760 
1761         zio_gang_tree_assemble(zio, bp, &zio->io_gang_tree);
1762 
1763         return (ZIO_PIPELINE_CONTINUE);
1764 }
1765 
1766 static int
1767 zio_gang_issue(zio_t *zio)
1768 {
1769         blkptr_t *bp = zio->io_bp;
1770 
1771         if (zio_wait_for_children(zio, ZIO_CHILD_GANG, ZIO_WAIT_DONE))
1772                 return (ZIO_PIPELINE_STOP);
1773 
1774         ASSERT(BP_IS_GANG(bp) && zio->io_gang_leader == zio);
1775         ASSERT(zio->io_child_type > ZIO_CHILD_GANG);
1776 
1777         if (zio->io_child_error[ZIO_CHILD_GANG] == 0)
1778                 zio_gang_tree_issue(zio, zio->io_gang_tree, bp, zio->io_data);
1779         else
1780                 zio_gang_tree_free(&zio->io_gang_tree);
1781 
1782         zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1783 
1784         return (ZIO_PIPELINE_CONTINUE);
1785 }
1786 
1787 static void
1788 zio_write_gang_member_ready(zio_t *zio)
1789 {
1790         zio_t *pio = zio_unique_parent(zio);
1791         zio_t *gio = zio->io_gang_leader;
1792         dva_t *cdva = zio->io_bp->blk_dva;
1793         dva_t *pdva = pio->io_bp->blk_dva;
1794         uint64_t asize;
1795 
1796         if (BP_IS_HOLE(zio->io_bp))
1797                 return;
1798 
1799         ASSERT(BP_IS_HOLE(&zio->io_bp_orig));
1800 
1801         ASSERT(zio->io_child_type == ZIO_CHILD_GANG);
1802         ASSERT3U(zio->io_prop.zp_copies, ==, gio->io_prop.zp_copies);
1803         ASSERT3U(zio->io_prop.zp_copies, <=, BP_GET_NDVAS(zio->io_bp));
1804         ASSERT3U(pio->io_prop.zp_copies, <=, BP_GET_NDVAS(pio->io_bp));
1805         ASSERT3U(BP_GET_NDVAS(zio->io_bp), <=, BP_GET_NDVAS(pio->io_bp));
1806 
1807         mutex_enter(&pio->io_lock);
1808         for (int d = 0; d < BP_GET_NDVAS(zio->io_bp); d++) {
1809                 ASSERT(DVA_GET_GANG(&pdva[d]));
1810                 asize = DVA_GET_ASIZE(&pdva[d]);
1811                 asize += DVA_GET_ASIZE(&cdva[d]);
1812                 DVA_SET_ASIZE(&pdva[d], asize);
1813         }
1814         mutex_exit(&pio->io_lock);
1815 }
1816 
1817 static int
1818 zio_write_gang_block(zio_t *pio)
1819 {
1820         spa_t *spa = pio->io_spa;
1821         blkptr_t *bp = pio->io_bp;
1822         zio_t *gio = pio->io_gang_leader;
1823         zio_t *zio;
1824         zio_gang_node_t *gn, **gnpp;
1825         zio_gbh_phys_t *gbh;
1826         uint64_t txg = pio->io_txg;
1827         uint64_t resid = pio->io_size;
1828         uint64_t lsize;
1829         int copies = gio->io_prop.zp_copies;
1830         int gbh_copies = MIN(copies + 1, spa_max_replication(spa));
1831         zio_prop_t zp;
1832         int error;
1833 
1834         error = metaslab_alloc(spa, spa_normal_class(spa), SPA_GANGBLOCKSIZE,
1835             bp, gbh_copies, txg, pio == gio ? NULL : gio->io_bp,
1836             METASLAB_HINTBP_FAVOR | METASLAB_GANG_HEADER);
1837         if (error) {
1838                 pio->io_error = error;
1839                 return (ZIO_PIPELINE_CONTINUE);
1840         }
1841 
1842         if (pio == gio) {
1843                 gnpp = &gio->io_gang_tree;
1844         } else {
1845                 gnpp = pio->io_private;
1846                 ASSERT(pio->io_ready == zio_write_gang_member_ready);
1847         }
1848 
1849         gn = zio_gang_node_alloc(gnpp);
1850         gbh = gn->gn_gbh;
1851         bzero(gbh, SPA_GANGBLOCKSIZE);
1852 
1853         /*
1854          * Create the gang header.
1855          */
1856         zio = zio_rewrite(pio, spa, txg, bp, gbh, SPA_GANGBLOCKSIZE, NULL, NULL,
1857             pio->io_priority, ZIO_GANG_CHILD_FLAGS(pio), &pio->io_bookmark);
1858 
1859         /*
1860          * Create and nowait the gang children.
1861          */
1862         for (int g = 0; resid != 0; resid -= lsize, g++) {
1863                 lsize = P2ROUNDUP(resid / (SPA_GBH_NBLKPTRS - g),
1864                     SPA_MINBLOCKSIZE);
1865                 ASSERT(lsize >= SPA_MINBLOCKSIZE && lsize <= resid);
1866 
1867                 zp.zp_checksum = gio->io_prop.zp_checksum;
1868                 zp.zp_compress = ZIO_COMPRESS_OFF;
1869                 zp.zp_type = DMU_OT_NONE;
1870                 zp.zp_level = 0;
1871                 zp.zp_copies = gio->io_prop.zp_copies;
1872                 zp.zp_dedup = B_FALSE;
1873                 zp.zp_dedup_verify = B_FALSE;
1874                 zp.zp_nopwrite = B_FALSE;
1875 
1876                 zio_nowait(zio_write(zio, spa, txg, &gbh->zg_blkptr[g],
1877                     (char *)pio->io_data + (pio->io_size - resid), lsize, &zp,
1878                     zio_write_gang_member_ready, NULL, NULL, &gn->gn_child[g],
1879                     pio->io_priority, ZIO_GANG_CHILD_FLAGS(pio),
1880                     &pio->io_bookmark));
1881         }
1882 
1883         /*
1884          * Set pio's pipeline to just wait for zio to finish.
1885          */
1886         pio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1887 
1888         zio_nowait(zio);
1889 
1890         return (ZIO_PIPELINE_CONTINUE);
1891 }
1892 
1893 /*
1894  * The zio_nop_write stage in the pipeline determines if allocating
1895  * a new bp is necessary.  By leveraging a cryptographically secure checksum,
1896  * such as SHA256, we can compare the checksums of the new data and the old
1897  * to determine if allocating a new block is required.  The nopwrite
1898  * feature can handle writes in either syncing or open context (i.e. zil
1899  * writes) and as a result is mutually exclusive with dedup.
1900  */
1901 static int
1902 zio_nop_write(zio_t *zio)
1903 {
1904         blkptr_t *bp = zio->io_bp;
1905         blkptr_t *bp_orig = &zio->io_bp_orig;
1906         zio_prop_t *zp = &zio->io_prop;
1907 
1908         ASSERT(BP_GET_LEVEL(bp) == 0);
1909         ASSERT(!(zio->io_flags & ZIO_FLAG_IO_REWRITE));
1910         ASSERT(zp->zp_nopwrite);
1911         ASSERT(!zp->zp_dedup);
1912         ASSERT(zio->io_bp_override == NULL);
1913         ASSERT(IO_IS_ALLOCATING(zio));
1914 
1915         /*
1916          * Check to see if the original bp and the new bp have matching
1917          * characteristics (i.e. same checksum, compression algorithms, etc).
1918          * If they don't then just continue with the pipeline which will
1919          * allocate a new bp.
1920          */
1921         if (BP_IS_HOLE(bp_orig) ||
1922             !zio_checksum_table[BP_GET_CHECKSUM(bp)].ci_dedup ||
1923             BP_GET_CHECKSUM(bp) != BP_GET_CHECKSUM(bp_orig) ||
1924             BP_GET_COMPRESS(bp) != BP_GET_COMPRESS(bp_orig) ||
1925             BP_GET_DEDUP(bp) != BP_GET_DEDUP(bp_orig) ||
1926             zp->zp_copies != BP_GET_NDVAS(bp_orig))
1927                 return (ZIO_PIPELINE_CONTINUE);
1928 
1929         /*
1930          * If the checksums match then reset the pipeline so that we
1931          * avoid allocating a new bp and issuing any I/O.
1932          */
1933         if (ZIO_CHECKSUM_EQUAL(bp->blk_cksum, bp_orig->blk_cksum)) {
1934                 ASSERT(zio_checksum_table[zp->zp_checksum].ci_dedup);
1935                 ASSERT3U(BP_GET_PSIZE(bp), ==, BP_GET_PSIZE(bp_orig));
1936                 ASSERT3U(BP_GET_LSIZE(bp), ==, BP_GET_LSIZE(bp_orig));
1937                 ASSERT(zp->zp_compress != ZIO_COMPRESS_OFF);
1938                 ASSERT(bcmp(&bp->blk_prop, &bp_orig->blk_prop,
1939                     sizeof (uint64_t)) == 0);
1940 
1941                 *bp = *bp_orig;
1942                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
1943                 zio->io_flags |= ZIO_FLAG_NOPWRITE;
1944         }
1945 
1946         return (ZIO_PIPELINE_CONTINUE);
1947 }
1948 
1949 /*
1950  * ==========================================================================
1951  * Dedup
1952  * ==========================================================================
1953  */
1954 static void
1955 zio_ddt_child_read_done(zio_t *zio)
1956 {
1957         blkptr_t *bp = zio->io_bp;
1958         ddt_entry_t *dde = zio->io_private;
1959         ddt_phys_t *ddp;
1960         zio_t *pio = zio_unique_parent(zio);
1961 
1962         mutex_enter(&pio->io_lock);
1963         ddp = ddt_phys_select(dde, bp);
1964         if (zio->io_error == 0)
1965                 ddt_phys_clear(ddp);    /* this ddp doesn't need repair */
1966         if (zio->io_error == 0 && dde->dde_repair_data == NULL)
1967                 dde->dde_repair_data = zio->io_data;
1968         else
1969                 zio_buf_free(zio->io_data, zio->io_size);
1970         mutex_exit(&pio->io_lock);
1971 }
1972 
1973 static int
1974 zio_ddt_read_start(zio_t *zio)
1975 {
1976         blkptr_t *bp = zio->io_bp;
1977 
1978         ASSERT(BP_GET_DEDUP(bp));
1979         ASSERT(BP_GET_PSIZE(bp) == zio->io_size);
1980         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
1981 
1982         if (zio->io_child_error[ZIO_CHILD_DDT]) {
1983                 ddt_t *ddt = ddt_select(zio->io_spa, bp);
1984                 ddt_entry_t *dde = ddt_repair_start(ddt, bp);
1985                 ddt_phys_t *ddp = dde->dde_phys;
1986                 ddt_phys_t *ddp_self = ddt_phys_select(dde, bp);
1987                 blkptr_t blk;
1988 
1989                 ASSERT(zio->io_vsd == NULL);
1990                 zio->io_vsd = dde;
1991 
1992                 if (ddp_self == NULL)
1993                         return (ZIO_PIPELINE_CONTINUE);
1994 
1995                 for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) {
1996                         if (ddp->ddp_phys_birth == 0 || ddp == ddp_self)
1997                                 continue;
1998                         ddt_bp_create(ddt->ddt_checksum, &dde->dde_key, ddp,
1999                             &blk);
2000                         zio_nowait(zio_read(zio, zio->io_spa, &blk,
2001                             zio_buf_alloc(zio->io_size), zio->io_size,
2002                             zio_ddt_child_read_done, dde, zio->io_priority,
2003                             ZIO_DDT_CHILD_FLAGS(zio) | ZIO_FLAG_DONT_PROPAGATE,
2004                             &zio->io_bookmark));
2005                 }
2006                 return (ZIO_PIPELINE_CONTINUE);
2007         }
2008 
2009         zio_nowait(zio_read(zio, zio->io_spa, bp,
2010             zio->io_data, zio->io_size, NULL, NULL, zio->io_priority,
2011             ZIO_DDT_CHILD_FLAGS(zio), &zio->io_bookmark));
2012 
2013         return (ZIO_PIPELINE_CONTINUE);
2014 }
2015 
2016 static int
2017 zio_ddt_read_done(zio_t *zio)
2018 {
2019         blkptr_t *bp = zio->io_bp;
2020 
2021         if (zio_wait_for_children(zio, ZIO_CHILD_DDT, ZIO_WAIT_DONE))
2022                 return (ZIO_PIPELINE_STOP);
2023 
2024         ASSERT(BP_GET_DEDUP(bp));
2025         ASSERT(BP_GET_PSIZE(bp) == zio->io_size);
2026         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
2027 
2028         if (zio->io_child_error[ZIO_CHILD_DDT]) {
2029                 ddt_t *ddt = ddt_select(zio->io_spa, bp);
2030                 ddt_entry_t *dde = zio->io_vsd;
2031                 if (ddt == NULL) {
2032                         ASSERT(spa_load_state(zio->io_spa) != SPA_LOAD_NONE);
2033                         return (ZIO_PIPELINE_CONTINUE);
2034                 }
2035                 if (dde == NULL) {
2036                         zio->io_stage = ZIO_STAGE_DDT_READ_START >> 1;
2037                         zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE, B_FALSE);
2038                         return (ZIO_PIPELINE_STOP);
2039                 }
2040                 if (dde->dde_repair_data != NULL) {
2041                         bcopy(dde->dde_repair_data, zio->io_data, zio->io_size);
2042                         zio->io_child_error[ZIO_CHILD_DDT] = 0;
2043                 }
2044                 ddt_repair_done(ddt, dde);
2045                 zio->io_vsd = NULL;
2046         }
2047 
2048         ASSERT(zio->io_vsd == NULL);
2049 
2050         return (ZIO_PIPELINE_CONTINUE);
2051 }
2052 
2053 static boolean_t
2054 zio_ddt_collision(zio_t *zio, ddt_t *ddt, ddt_entry_t *dde)
2055 {
2056         spa_t *spa = zio->io_spa;
2057 
2058         /*
2059          * Note: we compare the original data, not the transformed data,
2060          * because when zio->io_bp is an override bp, we will not have
2061          * pushed the I/O transforms.  That's an important optimization
2062          * because otherwise we'd compress/encrypt all dmu_sync() data twice.
2063          */
2064         for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++) {
2065                 zio_t *lio = dde->dde_lead_zio[p];
2066 
2067                 if (lio != NULL) {
2068                         return (lio->io_orig_size != zio->io_orig_size ||
2069                             bcmp(zio->io_orig_data, lio->io_orig_data,
2070                             zio->io_orig_size) != 0);
2071                 }
2072         }
2073 
2074         for (int p = DDT_PHYS_SINGLE; p <= DDT_PHYS_TRIPLE; p++) {
2075                 ddt_phys_t *ddp = &dde->dde_phys[p];
2076 
2077                 if (ddp->ddp_phys_birth != 0) {
2078                         arc_buf_t *abuf = NULL;
2079                         uint32_t aflags = ARC_WAIT;
2080                         blkptr_t blk = *zio->io_bp;
2081                         int error;
2082 
2083                         ddt_bp_fill(ddp, &blk, ddp->ddp_phys_birth);
2084 
2085                         ddt_exit(ddt);
2086 
2087                         error = arc_read(NULL, spa, &blk,
2088                             arc_getbuf_func, &abuf, ZIO_PRIORITY_SYNC_READ,
2089                             ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
2090                             &aflags, &zio->io_bookmark);
2091 
2092                         if (error == 0) {
2093                                 if (arc_buf_size(abuf) != zio->io_orig_size ||
2094                                     bcmp(abuf->b_data, zio->io_orig_data,
2095                                     zio->io_orig_size) != 0)
2096                                         error = SET_ERROR(EEXIST);
2097                                 VERIFY(arc_buf_remove_ref(abuf, &abuf));
2098                         }
2099 
2100                         ddt_enter(ddt);
2101                         return (error != 0);
2102                 }
2103         }
2104 
2105         return (B_FALSE);
2106 }
2107 
2108 static void
2109 zio_ddt_child_write_ready(zio_t *zio)
2110 {
2111         int p = zio->io_prop.zp_copies;
2112         ddt_t *ddt = ddt_select(zio->io_spa, zio->io_bp);
2113         ddt_entry_t *dde = zio->io_private;
2114         ddt_phys_t *ddp = &dde->dde_phys[p];
2115         zio_t *pio;
2116 
2117         if (zio->io_error)
2118                 return;
2119 
2120         ddt_enter(ddt);
2121 
2122         ASSERT(dde->dde_lead_zio[p] == zio);
2123 
2124         ddt_phys_fill(ddp, zio->io_bp);
2125 
2126         while ((pio = zio_walk_parents(zio)) != NULL)
2127                 ddt_bp_fill(ddp, pio->io_bp, zio->io_txg);
2128 
2129         ddt_exit(ddt);
2130 }
2131 
2132 static void
2133 zio_ddt_child_write_done(zio_t *zio)
2134 {
2135         int p = zio->io_prop.zp_copies;
2136         ddt_t *ddt = ddt_select(zio->io_spa, zio->io_bp);
2137         ddt_entry_t *dde = zio->io_private;
2138         ddt_phys_t *ddp = &dde->dde_phys[p];
2139 
2140         ddt_enter(ddt);
2141 
2142         ASSERT(ddp->ddp_refcnt == 0);
2143         ASSERT(dde->dde_lead_zio[p] == zio);
2144         dde->dde_lead_zio[p] = NULL;
2145 
2146         if (zio->io_error == 0) {
2147                 while (zio_walk_parents(zio) != NULL)
2148                         ddt_phys_addref(ddp);
2149         } else {
2150                 ddt_phys_clear(ddp);
2151         }
2152 
2153         ddt_exit(ddt);
2154 }
2155 
2156 static void
2157 zio_ddt_ditto_write_done(zio_t *zio)
2158 {
2159         int p = DDT_PHYS_DITTO;
2160         zio_prop_t *zp = &zio->io_prop;
2161         blkptr_t *bp = zio->io_bp;
2162         ddt_t *ddt = ddt_select(zio->io_spa, bp);
2163         ddt_entry_t *dde = zio->io_private;
2164         ddt_phys_t *ddp = &dde->dde_phys[p];
2165         ddt_key_t *ddk = &dde->dde_key;
2166 
2167         ddt_enter(ddt);
2168 
2169         ASSERT(ddp->ddp_refcnt == 0);
2170         ASSERT(dde->dde_lead_zio[p] == zio);
2171         dde->dde_lead_zio[p] = NULL;
2172 
2173         if (zio->io_error == 0) {
2174                 ASSERT(ZIO_CHECKSUM_EQUAL(bp->blk_cksum, ddk->ddk_cksum));
2175                 ASSERT(zp->zp_copies < SPA_DVAS_PER_BP);
2176                 ASSERT(zp->zp_copies == BP_GET_NDVAS(bp) - BP_IS_GANG(bp));
2177                 if (ddp->ddp_phys_birth != 0)
2178                         ddt_phys_free(ddt, ddk, ddp, zio->io_txg);
2179                 ddt_phys_fill(ddp, bp);
2180         }
2181 
2182         ddt_exit(ddt);
2183 }
2184 
2185 static int
2186 zio_ddt_write(zio_t *zio)
2187 {
2188         spa_t *spa = zio->io_spa;
2189         blkptr_t *bp = zio->io_bp;
2190         uint64_t txg = zio->io_txg;
2191         zio_prop_t *zp = &zio->io_prop;
2192         int p = zp->zp_copies;
2193         int ditto_copies;
2194         zio_t *cio = NULL;
2195         zio_t *dio = NULL;
2196         ddt_t *ddt = ddt_select(spa, bp);
2197         ddt_entry_t *dde;
2198         ddt_phys_t *ddp;
2199 
2200         ASSERT(BP_GET_DEDUP(bp));
2201         ASSERT(BP_GET_CHECKSUM(bp) == zp->zp_checksum);
2202         ASSERT(BP_IS_HOLE(bp) || zio->io_bp_override);
2203 
2204         ddt_enter(ddt);
2205         dde = ddt_lookup(ddt, bp, B_TRUE);
2206         ddp = &dde->dde_phys[p];
2207 
2208         if (zp->zp_dedup_verify && zio_ddt_collision(zio, ddt, dde)) {
2209                 /*
2210                  * If we're using a weak checksum, upgrade to a strong checksum
2211                  * and try again.  If we're already using a strong checksum,
2212                  * we can't resolve it, so just convert to an ordinary write.
2213                  * (And automatically e-mail a paper to Nature?)
2214                  */
2215                 if (!zio_checksum_table[zp->zp_checksum].ci_dedup) {
2216                         zp->zp_checksum = spa_dedup_checksum(spa);
2217                         zio_pop_transforms(zio);
2218                         zio->io_stage = ZIO_STAGE_OPEN;
2219                         BP_ZERO(bp);
2220                 } else {
2221                         zp->zp_dedup = B_FALSE;
2222                 }
2223                 zio->io_pipeline = ZIO_WRITE_PIPELINE;
2224                 ddt_exit(ddt);
2225                 return (ZIO_PIPELINE_CONTINUE);
2226         }
2227 
2228         ditto_copies = ddt_ditto_copies_needed(ddt, dde, ddp);
2229         ASSERT(ditto_copies < SPA_DVAS_PER_BP);
2230 
2231         if (ditto_copies > ddt_ditto_copies_present(dde) &&
2232             dde->dde_lead_zio[DDT_PHYS_DITTO] == NULL) {
2233                 zio_prop_t czp = *zp;
2234 
2235                 czp.zp_copies = ditto_copies;
2236 
2237                 /*
2238                  * If we arrived here with an override bp, we won't have run
2239                  * the transform stack, so we won't have the data we need to
2240                  * generate a child i/o.  So, toss the override bp and restart.
2241                  * This is safe, because using the override bp is just an
2242                  * optimization; and it's rare, so the cost doesn't matter.
2243                  */
2244                 if (zio->io_bp_override) {
2245                         zio_pop_transforms(zio);
2246                         zio->io_stage = ZIO_STAGE_OPEN;
2247                         zio->io_pipeline = ZIO_WRITE_PIPELINE;
2248                         zio->io_bp_override = NULL;
2249                         BP_ZERO(bp);
2250                         ddt_exit(ddt);
2251                         return (ZIO_PIPELINE_CONTINUE);
2252                 }
2253 
2254                 dio = zio_write(zio, spa, txg, bp, zio->io_orig_data,
2255                     zio->io_orig_size, &czp, NULL, NULL,
2256                     zio_ddt_ditto_write_done, dde, zio->io_priority,
2257                     ZIO_DDT_CHILD_FLAGS(zio), &zio->io_bookmark);
2258 
2259                 zio_push_transform(dio, zio->io_data, zio->io_size, 0, NULL);
2260                 dde->dde_lead_zio[DDT_PHYS_DITTO] = dio;
2261         }
2262 
2263         if (ddp->ddp_phys_birth != 0 || dde->dde_lead_zio[p] != NULL) {
2264                 if (ddp->ddp_phys_birth != 0)
2265                         ddt_bp_fill(ddp, bp, txg);
2266                 if (dde->dde_lead_zio[p] != NULL)
2267                         zio_add_child(zio, dde->dde_lead_zio[p]);
2268                 else
2269                         ddt_phys_addref(ddp);
2270         } else if (zio->io_bp_override) {
2271                 ASSERT(bp->blk_birth == txg);
2272                 ASSERT(BP_EQUAL(bp, zio->io_bp_override));
2273                 ddt_phys_fill(ddp, bp);
2274                 ddt_phys_addref(ddp);
2275         } else {
2276                 cio = zio_write(zio, spa, txg, bp, zio->io_orig_data,
2277                     zio->io_orig_size, zp, zio_ddt_child_write_ready, NULL,
2278                     zio_ddt_child_write_done, dde, zio->io_priority,
2279                     ZIO_DDT_CHILD_FLAGS(zio), &zio->io_bookmark);
2280 
2281                 zio_push_transform(cio, zio->io_data, zio->io_size, 0, NULL);
2282                 dde->dde_lead_zio[p] = cio;
2283         }
2284 
2285         ddt_exit(ddt);
2286 
2287         if (cio)
2288                 zio_nowait(cio);
2289         if (dio)
2290                 zio_nowait(dio);
2291 
2292         return (ZIO_PIPELINE_CONTINUE);
2293 }
2294 
2295 ddt_entry_t *freedde; /* for debugging */
2296 
2297 static int
2298 zio_ddt_free(zio_t *zio)
2299 {
2300         spa_t *spa = zio->io_spa;
2301         blkptr_t *bp = zio->io_bp;
2302         ddt_t *ddt = ddt_select(spa, bp);
2303         ddt_entry_t *dde;
2304         ddt_phys_t *ddp;
2305 
2306         ASSERT(BP_GET_DEDUP(bp));
2307         ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
2308 
2309         ddt_enter(ddt);
2310         freedde = dde = ddt_lookup(ddt, bp, B_TRUE);
2311         ddp = ddt_phys_select(dde, bp);
2312         ddt_phys_decref(ddp);
2313         ddt_exit(ddt);
2314 
2315         return (ZIO_PIPELINE_CONTINUE);
2316 }
2317 
2318 /*
2319  * ==========================================================================
2320  * Allocate and free blocks
2321  * ==========================================================================
2322  */
2323 static int
2324 zio_dva_allocate(zio_t *zio)
2325 {
2326         spa_t *spa = zio->io_spa;
2327         metaslab_class_t *mc = spa_normal_class(spa);
2328         blkptr_t *bp = zio->io_bp;
2329         int error;
2330         int flags = 0;
2331 
2332         if (zio->io_gang_leader == NULL) {
2333                 ASSERT(zio->io_child_type > ZIO_CHILD_GANG);
2334                 zio->io_gang_leader = zio;
2335         }
2336 
2337         ASSERT(BP_IS_HOLE(bp));
2338         ASSERT0(BP_GET_NDVAS(bp));
2339         ASSERT3U(zio->io_prop.zp_copies, >, 0);
2340         ASSERT3U(zio->io_prop.zp_copies, <=, spa_max_replication(spa));
2341         ASSERT3U(zio->io_size, ==, BP_GET_PSIZE(bp));
2342 
2343         /*
2344          * The dump device does not support gang blocks so allocation on
2345          * behalf of the dump device (i.e. ZIO_FLAG_NODATA) must avoid
2346          * the "fast" gang feature.
2347          */
2348         flags |= (zio->io_flags & ZIO_FLAG_NODATA) ? METASLAB_GANG_AVOID : 0;
2349         flags |= (zio->io_flags & ZIO_FLAG_GANG_CHILD) ?
2350             METASLAB_GANG_CHILD : 0;
2351         error = metaslab_alloc(spa, mc, zio->io_size, bp,
2352             zio->io_prop.zp_copies, zio->io_txg, NULL, flags);
2353 
2354         if (error) {
2355                 spa_dbgmsg(spa, "%s: metaslab allocation failure: zio %p, "
2356                     "size %llu, error %d", spa_name(spa), zio, zio->io_size,
2357                     error);
2358                 if (error == ENOSPC && zio->io_size > SPA_MINBLOCKSIZE)
2359                         return (zio_write_gang_block(zio));
2360                 zio->io_error = error;
2361         }
2362 
2363         return (ZIO_PIPELINE_CONTINUE);
2364 }
2365 
2366 static int
2367 zio_dva_free(zio_t *zio)
2368 {
2369         metaslab_free(zio->io_spa, zio->io_bp, zio->io_txg, B_FALSE);
2370 
2371         return (ZIO_PIPELINE_CONTINUE);
2372 }
2373 
2374 static int
2375 zio_dva_claim(zio_t *zio)
2376 {
2377         int error;
2378 
2379         error = metaslab_claim(zio->io_spa, zio->io_bp, zio->io_txg);
2380         if (error)
2381                 zio->io_error = error;
2382 
2383         return (ZIO_PIPELINE_CONTINUE);
2384 }
2385 
2386 /*
2387  * Undo an allocation.  This is used by zio_done() when an I/O fails
2388  * and we want to give back the block we just allocated.
2389  * This handles both normal blocks and gang blocks.
2390  */
2391 static void
2392 zio_dva_unallocate(zio_t *zio, zio_gang_node_t *gn, blkptr_t *bp)
2393 {
2394         ASSERT(bp->blk_birth == zio->io_txg || BP_IS_HOLE(bp));
2395         ASSERT(zio->io_bp_override == NULL);
2396 
2397         if (!BP_IS_HOLE(bp))
2398                 metaslab_free(zio->io_spa, bp, bp->blk_birth, B_TRUE);
2399 
2400         if (gn != NULL) {
2401                 for (int g = 0; g < SPA_GBH_NBLKPTRS; g++) {
2402                         zio_dva_unallocate(zio, gn->gn_child[g],
2403                             &gn->gn_gbh->zg_blkptr[g]);
2404                 }
2405         }
2406 }
2407 
2408 /*
2409  * Try to allocate an intent log block.  Return 0 on success, errno on failure.
2410  */
2411 int
2412 zio_alloc_zil(spa_t *spa, uint64_t txg, blkptr_t *new_bp, blkptr_t *old_bp,
2413     uint64_t size, boolean_t use_slog)
2414 {
2415         int error = 1;
2416 
2417         ASSERT(txg > spa_syncing_txg(spa));
2418 
2419         /*
2420          * ZIL blocks are always contiguous (i.e. not gang blocks) so we
2421          * set the METASLAB_GANG_AVOID flag so that they don't "fast gang"
2422          * when allocating them.
2423          */
2424         if (use_slog) {
2425                 error = metaslab_alloc(spa, spa_log_class(spa), size,
2426                     new_bp, 1, txg, old_bp,
2427                     METASLAB_HINTBP_AVOID | METASLAB_GANG_AVOID);
2428         }
2429 
2430         if (error) {
2431                 error = metaslab_alloc(spa, spa_normal_class(spa), size,
2432                     new_bp, 1, txg, old_bp,
2433                     METASLAB_HINTBP_AVOID);
2434         }
2435 
2436         if (error == 0) {
2437                 BP_SET_LSIZE(new_bp, size);
2438                 BP_SET_PSIZE(new_bp, size);
2439                 BP_SET_COMPRESS(new_bp, ZIO_COMPRESS_OFF);
2440                 BP_SET_CHECKSUM(new_bp,
2441                     spa_version(spa) >= SPA_VERSION_SLIM_ZIL
2442                     ? ZIO_CHECKSUM_ZILOG2 : ZIO_CHECKSUM_ZILOG);
2443                 BP_SET_TYPE(new_bp, DMU_OT_INTENT_LOG);
2444                 BP_SET_LEVEL(new_bp, 0);
2445                 BP_SET_DEDUP(new_bp, 0);
2446                 BP_SET_BYTEORDER(new_bp, ZFS_HOST_BYTEORDER);
2447         }
2448 
2449         return (error);
2450 }
2451 
2452 /*
2453  * Free an intent log block.
2454  */
2455 void
2456 zio_free_zil(spa_t *spa, uint64_t txg, blkptr_t *bp)
2457 {
2458         ASSERT(BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG);
2459         ASSERT(!BP_IS_GANG(bp));
2460 
2461         zio_free(spa, txg, bp);
2462 }
2463 
2464 /*
2465  * ==========================================================================
2466  * Read and write to physical devices
2467  * ==========================================================================
2468  */
2469 
2470 
2471 /*
2472  * Issue an I/O to the underlying vdev. Typically the issue pipeline
2473  * stops after this stage and will resume upon I/O completion.
2474  * However, there are instances where the vdev layer may need to
2475  * continue the pipeline when an I/O was not issued. Since the I/O
2476  * that was sent to the vdev layer might be different than the one
2477  * currently active in the pipeline (see vdev_queue_io()), we explicitly
2478  * force the underlying vdev layers to call either zio_execute() or
2479  * zio_interrupt() to ensure that the pipeline continues with the correct I/O.
2480  */
2481 static int
2482 zio_vdev_io_start(zio_t *zio)
2483 {
2484         vdev_t *vd = zio->io_vd;
2485         uint64_t align;
2486         spa_t *spa = zio->io_spa;
2487 
2488         ASSERT(zio->io_error == 0);
2489         ASSERT(zio->io_child_error[ZIO_CHILD_VDEV] == 0);
2490 
2491         if (vd == NULL) {
2492                 if (!(zio->io_flags & ZIO_FLAG_CONFIG_WRITER))
2493                         spa_config_enter(spa, SCL_ZIO, zio, RW_READER);
2494 
2495                 /*
2496                  * The mirror_ops handle multiple DVAs in a single BP.
2497                  */
2498                 vdev_mirror_ops.vdev_op_io_start(zio);
2499                 return (ZIO_PIPELINE_STOP);
2500         }
2501 
2502         /*
2503          * We keep track of time-sensitive I/Os so that the scan thread
2504          * can quickly react to certain workloads.  In particular, we care
2505          * about non-scrubbing, top-level reads and writes with the following
2506          * characteristics:
2507          *      - synchronous writes of user data to non-slog devices
2508          *      - any reads of user data
2509          * When these conditions are met, adjust the timestamp of spa_last_io
2510          * which allows the scan thread to adjust its workload accordingly.
2511          */
2512         if (!(zio->io_flags & ZIO_FLAG_SCAN_THREAD) && zio->io_bp != NULL &&
2513             vd == vd->vdev_top && !vd->vdev_islog &&
2514             zio->io_bookmark.zb_objset != DMU_META_OBJSET &&
2515             zio->io_txg != spa_syncing_txg(spa)) {
2516                 uint64_t old = spa->spa_last_io;
2517                 uint64_t new = ddi_get_lbolt64();
2518                 if (old != new)
2519                         (void) atomic_cas_64(&spa->spa_last_io, old, new);
2520         }
2521 
2522         align = 1ULL << vd->vdev_top->vdev_ashift;
2523 
2524         if (!(zio->io_flags & ZIO_FLAG_PHYSICAL) &&
2525             P2PHASE(zio->io_size, align) != 0) {
2526                 /* Transform logical writes to be a full physical block size. */
2527                 uint64_t asize = P2ROUNDUP(zio->io_size, align);
2528                 char *abuf = zio_buf_alloc(asize);
2529                 ASSERT(vd == vd->vdev_top);
2530                 if (zio->io_type == ZIO_TYPE_WRITE) {
2531                         bcopy(zio->io_data, abuf, zio->io_size);
2532                         bzero(abuf + zio->io_size, asize - zio->io_size);
2533                 }
2534                 zio_push_transform(zio, abuf, asize, asize, zio_subblock);
2535         }
2536 
2537         /*
2538          * If this is not a physical io, make sure that it is properly aligned
2539          * before proceeding.
2540          */
2541         if (!(zio->io_flags & ZIO_FLAG_PHYSICAL)) {
2542                 ASSERT0(P2PHASE(zio->io_offset, align));
2543                 ASSERT0(P2PHASE(zio->io_size, align));
2544         } else {
2545                 /*
2546                  * For physical writes, we allow 512b aligned writes and assume
2547                  * the device will perform a read-modify-write as necessary.
2548                  */
2549                 ASSERT0(P2PHASE(zio->io_offset, SPA_MINBLOCKSIZE));
2550                 ASSERT0(P2PHASE(zio->io_size, SPA_MINBLOCKSIZE));
2551         }
2552 
2553         VERIFY(zio->io_type != ZIO_TYPE_WRITE || spa_writeable(spa));
2554 
2555         /*
2556          * If this is a repair I/O, and there's no self-healing involved --
2557          * that is, we're just resilvering what we expect to resilver --
2558          * then don't do the I/O unless zio's txg is actually in vd's DTL.
2559          * This prevents spurious resilvering with nested replication.
2560          * For example, given a mirror of mirrors, (A+B)+(C+D), if only
2561          * A is out of date, we'll read from C+D, then use the data to
2562          * resilver A+B -- but we don't actually want to resilver B, just A.
2563          * The top-level mirror has no way to know this, so instead we just
2564          * discard unnecessary repairs as we work our way down the vdev tree.
2565          * The same logic applies to any form of nested replication:
2566          * ditto + mirror, RAID-Z + replacing, etc.  This covers them all.
2567          */
2568         if ((zio->io_flags & ZIO_FLAG_IO_REPAIR) &&
2569             !(zio->io_flags & ZIO_FLAG_SELF_HEAL) &&
2570             zio->io_txg != 0 &&      /* not a delegated i/o */
2571             !vdev_dtl_contains(vd, DTL_PARTIAL, zio->io_txg, 1)) {
2572                 ASSERT(zio->io_type == ZIO_TYPE_WRITE);
2573                 zio_vdev_io_bypass(zio);
2574                 return (ZIO_PIPELINE_CONTINUE);
2575         }
2576 
2577         if (vd->vdev_ops->vdev_op_leaf &&
2578             (zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE)) {
2579 
2580                 if (zio->io_type == ZIO_TYPE_READ && vdev_cache_read(zio))
2581                         return (ZIO_PIPELINE_CONTINUE);
2582 
2583                 if ((zio = vdev_queue_io(zio)) == NULL)
2584                         return (ZIO_PIPELINE_STOP);
2585 
2586                 if (!vdev_accessible(vd, zio)) {
2587                         zio->io_error = SET_ERROR(ENXIO);
2588                         zio_interrupt(zio);
2589                         return (ZIO_PIPELINE_STOP);
2590                 }
2591         }
2592 
2593         vd->vdev_ops->vdev_op_io_start(zio);
2594         return (ZIO_PIPELINE_STOP);
2595 }
2596 
2597 static int
2598 zio_vdev_io_done(zio_t *zio)
2599 {
2600         vdev_t *vd = zio->io_vd;
2601         vdev_ops_t *ops = vd ? vd->vdev_ops : &vdev_mirror_ops;
2602         boolean_t unexpected_error = B_FALSE;
2603 
2604         if (zio_wait_for_children(zio, ZIO_CHILD_VDEV, ZIO_WAIT_DONE))
2605                 return (ZIO_PIPELINE_STOP);
2606 
2607         ASSERT(zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE);
2608 
2609         if (vd != NULL && vd->vdev_ops->vdev_op_leaf) {
2610 
2611                 vdev_queue_io_done(zio);
2612 
2613                 if (zio->io_type == ZIO_TYPE_WRITE)
2614                         vdev_cache_write(zio);
2615 
2616                 if (zio_injection_enabled && zio->io_error == 0)
2617                         zio->io_error = zio_handle_device_injection(vd,
2618                             zio, EIO);
2619 
2620                 if (zio_injection_enabled && zio->io_error == 0)
2621                         zio->io_error = zio_handle_label_injection(zio, EIO);
2622 
2623                 if (zio->io_error) {
2624                         if (!vdev_accessible(vd, zio)) {
2625                                 zio->io_error = SET_ERROR(ENXIO);
2626                         } else {
2627                                 unexpected_error = B_TRUE;
2628                         }
2629                 }
2630         }
2631 
2632         ops->vdev_op_io_done(zio);
2633 
2634         if (unexpected_error)
2635                 VERIFY(vdev_probe(vd, zio) == NULL);
2636 
2637         return (ZIO_PIPELINE_CONTINUE);
2638 }
2639 
2640 /*
2641  * For non-raidz ZIOs, we can just copy aside the bad data read from the
2642  * disk, and use that to finish the checksum ereport later.
2643  */
2644 static void
2645 zio_vsd_default_cksum_finish(zio_cksum_report_t *zcr,
2646     const void *good_buf)
2647 {
2648         /* no processing needed */
2649         zfs_ereport_finish_checksum(zcr, good_buf, zcr->zcr_cbdata, B_FALSE);
2650 }
2651 
2652 /*ARGSUSED*/
2653 void
2654 zio_vsd_default_cksum_report(zio_t *zio, zio_cksum_report_t *zcr, void *ignored)
2655 {
2656         void *buf = zio_buf_alloc(zio->io_size);
2657 
2658         bcopy(zio->io_data, buf, zio->io_size);
2659 
2660         zcr->zcr_cbinfo = zio->io_size;
2661         zcr->zcr_cbdata = buf;
2662         zcr->zcr_finish = zio_vsd_default_cksum_finish;
2663         zcr->zcr_free = zio_buf_free;
2664 }
2665 
2666 static int
2667 zio_vdev_io_assess(zio_t *zio)
2668 {
2669         vdev_t *vd = zio->io_vd;
2670 
2671         if (zio_wait_for_children(zio, ZIO_CHILD_VDEV, ZIO_WAIT_DONE))
2672                 return (ZIO_PIPELINE_STOP);
2673 
2674         if (vd == NULL && !(zio->io_flags & ZIO_FLAG_CONFIG_WRITER))
2675                 spa_config_exit(zio->io_spa, SCL_ZIO, zio);
2676 
2677         if (zio->io_vsd != NULL) {
2678                 zio->io_vsd_ops->vsd_free(zio);
2679                 zio->io_vsd = NULL;
2680         }
2681 
2682         if (zio_injection_enabled && zio->io_error == 0)
2683                 zio->io_error = zio_handle_fault_injection(zio, EIO);
2684 
2685         /*
2686          * If the I/O failed, determine whether we should attempt to retry it.
2687          *
2688          * On retry, we cut in line in the issue queue, since we don't want
2689          * compression/checksumming/etc. work to prevent our (cheap) IO reissue.
2690          */
2691         if (zio->io_error && vd == NULL &&
2692             !(zio->io_flags & (ZIO_FLAG_DONT_RETRY | ZIO_FLAG_IO_RETRY))) {
2693                 ASSERT(!(zio->io_flags & ZIO_FLAG_DONT_QUEUE));  /* not a leaf */
2694                 ASSERT(!(zio->io_flags & ZIO_FLAG_IO_BYPASS));   /* not a leaf */
2695                 zio->io_error = 0;
2696                 zio->io_flags |= ZIO_FLAG_IO_RETRY |
2697                     ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_AGGREGATE;
2698                 zio->io_stage = ZIO_STAGE_VDEV_IO_START >> 1;
2699                 zio_taskq_dispatch(zio, ZIO_TASKQ_ISSUE,
2700                     zio_requeue_io_start_cut_in_line);
2701                 return (ZIO_PIPELINE_STOP);
2702         }
2703 
2704         /*
2705          * If we got an error on a leaf device, convert it to ENXIO
2706          * if the device is not accessible at all.
2707          */
2708         if (zio->io_error && vd != NULL && vd->vdev_ops->vdev_op_leaf &&
2709             !vdev_accessible(vd, zio))
2710                 zio->io_error = SET_ERROR(ENXIO);
2711 
2712         /*
2713          * If we can't write to an interior vdev (mirror or RAID-Z),
2714          * set vdev_cant_write so that we stop trying to allocate from it.
2715          */
2716         if (zio->io_error == ENXIO && zio->io_type == ZIO_TYPE_WRITE &&
2717             vd != NULL && !vd->vdev_ops->vdev_op_leaf) {
2718                 vd->vdev_cant_write = B_TRUE;
2719         }
2720 
2721         if (zio->io_error)
2722                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
2723 
2724         if (vd != NULL && vd->vdev_ops->vdev_op_leaf &&
2725             zio->io_physdone != NULL) {
2726                 ASSERT(!(zio->io_flags & ZIO_FLAG_DELEGATED));
2727                 ASSERT(zio->io_child_type == ZIO_CHILD_VDEV);
2728                 zio->io_physdone(zio->io_logical);
2729         }
2730 
2731         return (ZIO_PIPELINE_CONTINUE);
2732 }
2733 
2734 void
2735 zio_vdev_io_reissue(zio_t *zio)
2736 {
2737         ASSERT(zio->io_stage == ZIO_STAGE_VDEV_IO_START);
2738         ASSERT(zio->io_error == 0);
2739 
2740         zio->io_stage >>= 1;
2741 }
2742 
2743 void
2744 zio_vdev_io_redone(zio_t *zio)
2745 {
2746         ASSERT(zio->io_stage == ZIO_STAGE_VDEV_IO_DONE);
2747 
2748         zio->io_stage >>= 1;
2749 }
2750 
2751 void
2752 zio_vdev_io_bypass(zio_t *zio)
2753 {
2754         ASSERT(zio->io_stage == ZIO_STAGE_VDEV_IO_START);
2755         ASSERT(zio->io_error == 0);
2756 
2757         zio->io_flags |= ZIO_FLAG_IO_BYPASS;
2758         zio->io_stage = ZIO_STAGE_VDEV_IO_ASSESS >> 1;
2759 }
2760 
2761 /*
2762  * ==========================================================================
2763  * Generate and verify checksums
2764  * ==========================================================================
2765  */
2766 static int
2767 zio_checksum_generate(zio_t *zio)
2768 {
2769         blkptr_t *bp = zio->io_bp;
2770         enum zio_checksum checksum;
2771 
2772         if (bp == NULL) {
2773                 /*
2774                  * This is zio_write_phys().
2775                  * We're either generating a label checksum, or none at all.
2776                  */
2777                 checksum = zio->io_prop.zp_checksum;
2778 
2779                 if (checksum == ZIO_CHECKSUM_OFF)
2780                         return (ZIO_PIPELINE_CONTINUE);
2781 
2782                 ASSERT(checksum == ZIO_CHECKSUM_LABEL);
2783         } else {
2784                 if (BP_IS_GANG(bp) && zio->io_child_type == ZIO_CHILD_GANG) {
2785                         ASSERT(!IO_IS_ALLOCATING(zio));
2786                         checksum = ZIO_CHECKSUM_GANG_HEADER;
2787                 } else {
2788                         checksum = BP_GET_CHECKSUM(bp);
2789                 }
2790         }
2791 
2792         zio_checksum_compute(zio, checksum, zio->io_data, zio->io_size);
2793 
2794         return (ZIO_PIPELINE_CONTINUE);
2795 }
2796 
2797 static int
2798 zio_checksum_verify(zio_t *zio)
2799 {
2800         zio_bad_cksum_t info;
2801         blkptr_t *bp = zio->io_bp;
2802         int error;
2803 
2804         ASSERT(zio->io_vd != NULL);
2805 
2806         if (bp == NULL) {
2807                 /*
2808                  * This is zio_read_phys().
2809                  * We're either verifying a label checksum, or nothing at all.
2810                  */
2811                 if (zio->io_prop.zp_checksum == ZIO_CHECKSUM_OFF)
2812                         return (ZIO_PIPELINE_CONTINUE);
2813 
2814                 ASSERT(zio->io_prop.zp_checksum == ZIO_CHECKSUM_LABEL);
2815         }
2816 
2817         if ((error = zio_checksum_error(zio, &info)) != 0) {
2818                 zio->io_error = error;
2819                 if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE)) {
2820                         zfs_ereport_start_checksum(zio->io_spa,
2821                             zio->io_vd, zio, zio->io_offset,
2822                             zio->io_size, NULL, &info);
2823                 }
2824         }
2825 
2826         return (ZIO_PIPELINE_CONTINUE);
2827 }
2828 
2829 /*
2830  * Called by RAID-Z to ensure we don't compute the checksum twice.
2831  */
2832 void
2833 zio_checksum_verified(zio_t *zio)
2834 {
2835         zio->io_pipeline &= ~ZIO_STAGE_CHECKSUM_VERIFY;
2836 }
2837 
2838 /*
2839  * ==========================================================================
2840  * Error rank.  Error are ranked in the order 0, ENXIO, ECKSUM, EIO, other.
2841  * An error of 0 indicates success.  ENXIO indicates whole-device failure,
2842  * which may be transient (e.g. unplugged) or permament.  ECKSUM and EIO
2843  * indicate errors that are specific to one I/O, and most likely permanent.
2844  * Any other error is presumed to be worse because we weren't expecting it.
2845  * ==========================================================================
2846  */
2847 int
2848 zio_worst_error(int e1, int e2)
2849 {
2850         static int zio_error_rank[] = { 0, ENXIO, ECKSUM, EIO };
2851         int r1, r2;
2852 
2853         for (r1 = 0; r1 < sizeof (zio_error_rank) / sizeof (int); r1++)
2854                 if (e1 == zio_error_rank[r1])
2855                         break;
2856 
2857         for (r2 = 0; r2 < sizeof (zio_error_rank) / sizeof (int); r2++)
2858                 if (e2 == zio_error_rank[r2])
2859                         break;
2860 
2861         return (r1 > r2 ? e1 : e2);
2862 }
2863 
2864 /*
2865  * ==========================================================================
2866  * I/O completion
2867  * ==========================================================================
2868  */
2869 static int
2870 zio_ready(zio_t *zio)
2871 {
2872         blkptr_t *bp = zio->io_bp;
2873         zio_t *pio, *pio_next;
2874 
2875         if (zio_wait_for_children(zio, ZIO_CHILD_GANG, ZIO_WAIT_READY) ||
2876             zio_wait_for_children(zio, ZIO_CHILD_DDT, ZIO_WAIT_READY))
2877                 return (ZIO_PIPELINE_STOP);
2878 
2879         if (zio->io_ready) {
2880                 ASSERT(IO_IS_ALLOCATING(zio));
2881                 ASSERT(bp->blk_birth == zio->io_txg || BP_IS_HOLE(bp) ||
2882                     (zio->io_flags & ZIO_FLAG_NOPWRITE));
2883                 ASSERT(zio->io_children[ZIO_CHILD_GANG][ZIO_WAIT_READY] == 0);
2884 
2885                 zio->io_ready(zio);
2886         }
2887 
2888         if (bp != NULL && bp != &zio->io_bp_copy)
2889                 zio->io_bp_copy = *bp;
2890 
2891         if (zio->io_error)
2892                 zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;
2893 
2894         mutex_enter(&zio->io_lock);
2895         zio->io_state[ZIO_WAIT_READY] = 1;
2896         pio = zio_walk_parents(zio);
2897         mutex_exit(&zio->io_lock);
2898 
2899         /*
2900          * As we notify zio's parents, new parents could be added.
2901          * New parents go to the head of zio's io_parent_list, however,
2902          * so we will (correctly) not notify them.  The remainder of zio's
2903          * io_parent_list, from 'pio_next' onward, cannot change because
2904          * all parents must wait for us to be done before they can be done.
2905          */
2906         for (; pio != NULL; pio = pio_next) {
2907                 pio_next = zio_walk_parents(zio);
2908                 zio_notify_parent(pio, zio, ZIO_WAIT_READY);
2909         }
2910 
2911         if (zio->io_flags & ZIO_FLAG_NODATA) {
2912                 if (BP_IS_GANG(bp)) {
2913                         zio->io_flags &= ~ZIO_FLAG_NODATA;
2914                 } else {
2915                         ASSERT((uintptr_t)zio->io_data < SPA_MAXBLOCKSIZE);
2916                         zio->io_pipeline &= ~ZIO_VDEV_IO_STAGES;
2917                 }
2918         }
2919 
2920         if (zio_injection_enabled &&
2921             zio->io_spa->spa_syncing_txg == zio->io_txg)
2922                 zio_handle_ignored_writes(zio);
2923 
2924         return (ZIO_PIPELINE_CONTINUE);
2925 }
2926 
2927 static int
2928 zio_done(zio_t *zio)
2929 {
2930         spa_t *spa = zio->io_spa;
2931         zio_t *lio = zio->io_logical;
2932         blkptr_t *bp = zio->io_bp;
2933         vdev_t *vd = zio->io_vd;
2934         uint64_t psize = zio->io_size;
2935         zio_t *pio, *pio_next;
2936 
2937         /*
2938          * If our children haven't all completed,
2939          * wait for them and then repeat this pipeline stage.
2940          */
2941         if (zio_wait_for_children(zio, ZIO_CHILD_VDEV, ZIO_WAIT_DONE) ||
2942             zio_wait_for_children(zio, ZIO_CHILD_GANG, ZIO_WAIT_DONE) ||
2943             zio_wait_for_children(zio, ZIO_CHILD_DDT, ZIO_WAIT_DONE) ||
2944             zio_wait_for_children(zio, ZIO_CHILD_LOGICAL, ZIO_WAIT_DONE))
2945                 return (ZIO_PIPELINE_STOP);
2946 
2947         for (int c = 0; c < ZIO_CHILD_TYPES; c++)
2948                 for (int w = 0; w < ZIO_WAIT_TYPES; w++)
2949                         ASSERT(zio->io_children[c][w] == 0);
2950 
2951         if (bp != NULL && !BP_IS_EMBEDDED(bp)) {
2952                 ASSERT(bp->blk_pad[0] == 0);
2953                 ASSERT(bp->blk_pad[1] == 0);
2954                 ASSERT(bcmp(bp, &zio->io_bp_copy, sizeof (blkptr_t)) == 0 ||
2955                     (bp == zio_unique_parent(zio)->io_bp));
2956                 if (zio->io_type == ZIO_TYPE_WRITE && !BP_IS_HOLE(bp) &&
2957                     zio->io_bp_override == NULL &&
2958                     !(zio->io_flags & ZIO_FLAG_IO_REPAIR)) {
2959                         ASSERT(!BP_SHOULD_BYTESWAP(bp));
2960                         ASSERT3U(zio->io_prop.zp_copies, <=, BP_GET_NDVAS(bp));
2961                         ASSERT(BP_COUNT_GANG(bp) == 0 ||
2962                             (BP_COUNT_GANG(bp) == BP_GET_NDVAS(bp)));
2963                 }
2964                 if (zio->io_flags & ZIO_FLAG_NOPWRITE)
2965                         VERIFY(BP_EQUAL(bp, &zio->io_bp_orig));
2966         }
2967 
2968         /*
2969          * If there were child vdev/gang/ddt errors, they apply to us now.
2970          */
2971         zio_inherit_child_errors(zio, ZIO_CHILD_VDEV);
2972         zio_inherit_child_errors(zio, ZIO_CHILD_GANG);
2973         zio_inherit_child_errors(zio, ZIO_CHILD_DDT);
2974 
2975         /*
2976          * If the I/O on the transformed data was successful, generate any
2977          * checksum reports now while we still have the transformed data.
2978          */
2979         if (zio->io_error == 0) {
2980                 while (zio->io_cksum_report != NULL) {
2981                         zio_cksum_report_t *zcr = zio->io_cksum_report;
2982                         uint64_t align = zcr->zcr_align;
2983                         uint64_t asize = P2ROUNDUP(psize, align);
2984                         char *abuf = zio->io_data;
2985 
2986                         if (asize != psize) {
2987                                 abuf = zio_buf_alloc(asize);
2988                                 bcopy(zio->io_data, abuf, psize);
2989                                 bzero(abuf + psize, asize - psize);
2990                         }
2991 
2992                         zio->io_cksum_report = zcr->zcr_next;
2993                         zcr->zcr_next = NULL;
2994                         zcr->zcr_finish(zcr, abuf);
2995                         zfs_ereport_free_checksum(zcr);
2996 
2997                         if (asize != psize)
2998                                 zio_buf_free(abuf, asize);
2999                 }
3000         }
3001 
3002         zio_pop_transforms(zio);        /* note: may set zio->io_error */
3003 
3004         vdev_stat_update(zio, psize);
3005 
3006         if (zio->io_error) {
3007                 /*
3008                  * If this I/O is attached to a particular vdev,
3009                  * generate an error message describing the I/O failure
3010                  * at the block level.  We ignore these errors if the
3011                  * device is currently unavailable.
3012                  */
3013                 if (zio->io_error != ECKSUM && vd != NULL && !vdev_is_dead(vd))
3014                         zfs_ereport_post(FM_EREPORT_ZFS_IO, spa, vd, zio, 0, 0);
3015 
3016                 if ((zio->io_error == EIO || !(zio->io_flags &
3017                     (ZIO_FLAG_SPECULATIVE | ZIO_FLAG_DONT_PROPAGATE))) &&
3018                     zio == lio) {
3019                         /*
3020                          * For logical I/O requests, tell the SPA to log the
3021                          * error and generate a logical data ereport.
3022                          */
3023                         spa_log_error(spa, zio);
3024                         zfs_ereport_post(FM_EREPORT_ZFS_DATA, spa, NULL, zio,
3025                             0, 0);
3026                 }
3027         }
3028 
3029         if (zio->io_error && zio == lio) {
3030                 /*
3031                  * Determine whether zio should be reexecuted.  This will
3032                  * propagate all the way to the root via zio_notify_parent().
3033                  */
3034                 ASSERT(vd == NULL && bp != NULL);
3035                 ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
3036 
3037                 if (IO_IS_ALLOCATING(zio) &&
3038                     !(zio->io_flags & ZIO_FLAG_CANFAIL)) {
3039                         if (zio->io_error != ENOSPC)
3040                                 zio->io_reexecute |= ZIO_REEXECUTE_NOW;
3041                         else
3042                                 zio->io_reexecute |= ZIO_REEXECUTE_SUSPEND;
3043                 }
3044 
3045                 if ((zio->io_type == ZIO_TYPE_READ ||
3046                     zio->io_type == ZIO_TYPE_FREE) &&
3047                     !(zio->io_flags & ZIO_FLAG_SCAN_THREAD) &&
3048                     zio->io_error == ENXIO &&
3049                     spa_load_state(spa) == SPA_LOAD_NONE &&
3050                     spa_get_failmode(spa) != ZIO_FAILURE_MODE_CONTINUE)
3051                         zio->io_reexecute |= ZIO_REEXECUTE_SUSPEND;
3052 
3053                 if (!(zio->io_flags & ZIO_FLAG_CANFAIL) && !zio->io_reexecute)
3054                         zio->io_reexecute |= ZIO_REEXECUTE_SUSPEND;
3055 
3056                 /*
3057                  * Here is a possibly good place to attempt to do
3058                  * either combinatorial reconstruction or error correction
3059                  * based on checksums.  It also might be a good place
3060                  * to send out preliminary ereports before we suspend
3061                  * processing.
3062                  */
3063         }
3064 
3065         /*
3066          * If there were logical child errors, they apply to us now.
3067          * We defer this until now to avoid conflating logical child
3068          * errors with errors that happened to the zio itself when
3069          * updating vdev stats and reporting FMA events above.
3070          */
3071         zio_inherit_child_errors(zio, ZIO_CHILD_LOGICAL);
3072 
3073         if ((zio->io_error || zio->io_reexecute) &&
3074             IO_IS_ALLOCATING(zio) && zio->io_gang_leader == zio &&
3075             !(zio->io_flags & (ZIO_FLAG_IO_REWRITE | ZIO_FLAG_NOPWRITE)))
3076                 zio_dva_unallocate(zio, zio->io_gang_tree, bp);
3077 
3078         zio_gang_tree_free(&zio->io_gang_tree);
3079 
3080         /*
3081          * Godfather I/Os should never suspend.
3082          */
3083         if ((zio->io_flags & ZIO_FLAG_GODFATHER) &&
3084             (zio->io_reexecute & ZIO_REEXECUTE_SUSPEND))
3085                 zio->io_reexecute = 0;
3086 
3087         if (zio->io_reexecute) {
3088                 /*
3089                  * This is a logical I/O that wants to reexecute.
3090                  *
3091                  * Reexecute is top-down.  When an i/o fails, if it's not
3092                  * the root, it simply notifies its parent and sticks around.
3093                  * The parent, seeing that it still has children in zio_done(),
3094                  * does the same.  This percolates all the way up to the root.
3095                  * The root i/o will reexecute or suspend the entire tree.
3096                  *
3097                  * This approach ensures that zio_reexecute() honors
3098                  * all the original i/o dependency relationships, e.g.
3099                  * parents not executing until children are ready.
3100                  */
3101                 ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
3102 
3103                 zio->io_gang_leader = NULL;
3104 
3105                 mutex_enter(&zio->io_lock);
3106                 zio->io_state[ZIO_WAIT_DONE] = 1;
3107                 mutex_exit(&zio->io_lock);
3108 
3109                 /*
3110                  * "The Godfather" I/O monitors its children but is
3111                  * not a true parent to them. It will track them through
3112                  * the pipeline but severs its ties whenever they get into
3113                  * trouble (e.g. suspended). This allows "The Godfather"
3114                  * I/O to return status without blocking.
3115                  */
3116                 for (pio = zio_walk_parents(zio); pio != NULL; pio = pio_next) {
3117                         zio_link_t *zl = zio->io_walk_link;
3118                         pio_next = zio_walk_parents(zio);
3119 
3120                         if ((pio->io_flags & ZIO_FLAG_GODFATHER) &&
3121                             (zio->io_reexecute & ZIO_REEXECUTE_SUSPEND)) {
3122                                 zio_remove_child(pio, zio, zl);
3123                                 zio_notify_parent(pio, zio, ZIO_WAIT_DONE);
3124                         }
3125                 }
3126 
3127                 if ((pio = zio_unique_parent(zio)) != NULL) {
3128                         /*
3129                          * We're not a root i/o, so there's nothing to do
3130                          * but notify our parent.  Don't propagate errors
3131                          * upward since we haven't permanently failed yet.
3132                          */
3133                         ASSERT(!(zio->io_flags & ZIO_FLAG_GODFATHER));
3134                         zio->io_flags |= ZIO_FLAG_DONT_PROPAGATE;
3135                         zio_notify_parent(pio, zio, ZIO_WAIT_DONE);
3136                 } else if (zio->io_reexecute & ZIO_REEXECUTE_SUSPEND) {
3137                         /*
3138                          * We'd fail again if we reexecuted now, so suspend
3139                          * until conditions improve (e.g. device comes online).
3140                          */
3141                         zio_suspend(spa, zio);
3142                 } else {
3143                         /*
3144                          * Reexecution is potentially a huge amount of work.
3145                          * Hand it off to the otherwise-unused claim taskq.
3146                          */
3147                         ASSERT(zio->io_tqent.tqent_next == NULL);
3148                         spa_taskq_dispatch_ent(spa, ZIO_TYPE_CLAIM,
3149                             ZIO_TASKQ_ISSUE, (task_func_t *)zio_reexecute, zio,
3150                             0, &zio->io_tqent);
3151                 }
3152                 return (ZIO_PIPELINE_STOP);
3153         }
3154 
3155         ASSERT(zio->io_child_count == 0);
3156         ASSERT(zio->io_reexecute == 0);
3157         ASSERT(zio->io_error == 0 || (zio->io_flags & ZIO_FLAG_CANFAIL));
3158 
3159         /*
3160          * Report any checksum errors, since the I/O is complete.
3161          */
3162         while (zio->io_cksum_report != NULL) {
3163                 zio_cksum_report_t *zcr = zio->io_cksum_report;
3164                 zio->io_cksum_report = zcr->zcr_next;
3165                 zcr->zcr_next = NULL;
3166                 zcr->zcr_finish(zcr, NULL);
3167                 zfs_ereport_free_checksum(zcr);
3168         }
3169 
3170         /*
3171          * It is the responsibility of the done callback to ensure that this
3172          * particular zio is no longer discoverable for adoption, and as
3173          * such, cannot acquire any new parents.
3174          */
3175         if (zio->io_done)
3176                 zio->io_done(zio);
3177 
3178         mutex_enter(&zio->io_lock);
3179         zio->io_state[ZIO_WAIT_DONE] = 1;
3180         mutex_exit(&zio->io_lock);
3181 
3182         for (pio = zio_walk_parents(zio); pio != NULL; pio = pio_next) {
3183                 zio_link_t *zl = zio->io_walk_link;
3184                 pio_next = zio_walk_parents(zio);
3185                 zio_remove_child(pio, zio, zl);
3186                 zio_notify_parent(pio, zio, ZIO_WAIT_DONE);
3187         }
3188 
3189         if (zio->io_waiter != NULL) {
3190                 mutex_enter(&zio->io_lock);
3191                 zio->io_executor = NULL;
3192                 cv_broadcast(&zio->io_cv);
3193                 mutex_exit(&zio->io_lock);
3194         } else {
3195                 zio_destroy(zio);
3196         }
3197 
3198         return (ZIO_PIPELINE_STOP);
3199 }
3200 
3201 /*
3202  * ==========================================================================
3203  * I/O pipeline definition
3204  * ==========================================================================
3205  */
3206 static zio_pipe_stage_t *zio_pipeline[] = {
3207         NULL,
3208         zio_read_bp_init,
3209         zio_free_bp_init,
3210         zio_issue_async,
3211         zio_write_bp_init,
3212         zio_checksum_generate,
3213         zio_nop_write,
3214         zio_ddt_read_start,
3215         zio_ddt_read_done,
3216         zio_ddt_write,
3217         zio_ddt_free,
3218         zio_gang_assemble,
3219         zio_gang_issue,
3220         zio_dva_allocate,
3221         zio_dva_free,
3222         zio_dva_claim,
3223         zio_ready,
3224         zio_vdev_io_start,
3225         zio_vdev_io_done,
3226         zio_vdev_io_assess,
3227         zio_checksum_verify,
3228         zio_done
3229 };
3230 
3231 /* dnp is the dnode for zb1->zb_object */
3232 boolean_t
3233 zbookmark_is_before(const dnode_phys_t *dnp, const zbookmark_phys_t *zb1,
3234     const zbookmark_phys_t *zb2)
3235 {
3236         uint64_t zb1nextL0, zb2thisobj;
3237 
3238         ASSERT(zb1->zb_objset == zb2->zb_objset);
3239         ASSERT(zb2->zb_level == 0);
3240 
3241         /* The objset_phys_t isn't before anything. */
3242         if (dnp == NULL)
3243                 return (B_FALSE);
3244 
3245         zb1nextL0 = (zb1->zb_blkid + 1) <<
3246             ((zb1->zb_level) * (dnp->dn_indblkshift - SPA_BLKPTRSHIFT));
3247 
3248         zb2thisobj = zb2->zb_object ? zb2->zb_object :
3249             zb2->zb_blkid << (DNODE_BLOCK_SHIFT - DNODE_SHIFT);
3250 
3251         if (zb1->zb_object == DMU_META_DNODE_OBJECT) {
3252                 uint64_t nextobj = zb1nextL0 *
3253                     (dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT) >> DNODE_SHIFT;
3254                 return (nextobj <= zb2thisobj);
3255         }
3256 
3257         if (zb1->zb_object < zb2thisobj)
3258                 return (B_TRUE);
3259         if (zb1->zb_object > zb2thisobj)
3260                 return (B_FALSE);
3261         if (zb2->zb_object == DMU_META_DNODE_OBJECT)
3262                 return (B_FALSE);
3263         return (zb1nextL0 <= zb2->zb_blkid);
3264 }