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