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 2009 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25 
  26 #include <sys/types.h>
  27 #include <sys/debug.h>
  28 #include <sys/ksynch.h>
  29 #include <sys/kmem.h>
  30 #include <sys/cmn_err.h>
  31 #include <sys/errno.h>
  32 #include <sys/ddi.h>
  33 
  34 #include <sys/ncall/ncall.h>
  35 
  36 #define __NSC_GEN__
  37 #include "nsc_dev.h"
  38 
  39 #ifdef DS_DDICT
  40 #include "../contract.h"
  41 #endif
  42 
  43 #include "../nsctl.h"
  44 
  45 #define NSC_DEVMIN      "DevMin"
  46 #define NSC_DEVMAJ      "DevMaj"
  47 
  48 #define _I(x)   (((long)(&((nsc_io_t *)0)->x))/sizeof (long))
  49 #define _F(x)   (((long)(&((nsc_fd_t *)0)->x))/sizeof (long))
  50 
  51 
  52 nsc_def_t _nsc_io_def[] = {
  53         "Open",         (uintptr_t)nsc_null,    _I(open),
  54         "Close",        (uintptr_t)nsc_null,    _I(close),
  55         "Attach",       (uintptr_t)nsc_null,    _I(attach),
  56         "Detach",       (uintptr_t)nsc_null,    _I(detach),
  57         "Flush",        (uintptr_t)nsc_null,    _I(flush),
  58         "Provide",      0,              _I(provide),
  59         0,              0,              0
  60 };
  61 
  62 nsc_def_t _nsc_fd_def[] = {
  63         "Pinned",       (uintptr_t)nsc_null,    _F(sf_pinned),
  64         "Unpinned",     (uintptr_t)nsc_null,    _F(sf_unpinned),
  65         "Attach",       (uintptr_t)nsc_null,    _F(sf_attach),
  66         "Detach",       (uintptr_t)nsc_null,    _F(sf_detach),
  67         "Flush",        (uintptr_t)nsc_null,    _F(sf_flush),
  68         0,              0,              0
  69 };
  70 
  71 kmutex_t _nsc_io_lock;
  72 kmutex_t _nsc_devval_lock;
  73 
  74 nsc_io_t *_nsc_io_top = NULL;
  75 nsc_io_t *_nsc_null_io = NULL;
  76 nsc_dev_t *_nsc_dev_top = NULL;
  77 nsc_dev_t *_nsc_dev_pend = NULL;
  78 nsc_path_t *_nsc_path_top = NULL;
  79 nsc_devval_t *_nsc_devval_top = NULL;
  80 
  81 extern nsc_def_t _nsc_disk_def[];
  82 extern nsc_def_t _nsc_cache_def[];
  83 
  84 extern nsc_mem_t *_nsc_local_mem;
  85 extern nsc_rmmap_t *_nsc_global_map;
  86 
  87 static clock_t _nsc_io_lbolt;
  88 
  89 static nsc_io_t *_nsc_find_io(char *, int, int *);
  90 nsc_io_t *_nsc_reserve_io(char *, int);
  91 static nsc_io_t *_nsc_alloc_io(int, char *, int);
  92 
  93 static int _nsc_open_fn(nsc_fd_t *, int);
  94 static int _nsc_close_fn(nsc_fd_t *);
  95 static int _nsc_alloc_fd(char *, int, int, nsc_fd_t **);
  96 static int _nsc_alloc_iodev(nsc_dev_t *, int, nsc_iodev_t **);
  97 static int _nsc_alloc_dev(char *, nsc_dev_t **);
  98 static int _nsc_reopen_io(char *, int);
  99 static int _nsc_reopen_dev(nsc_dev_t *, int);
 100 static int _nsc_relock_dev(nsc_dev_t *, nsc_fd_t *, nsc_iodev_t *);
 101 static int _nsc_reopen_fd(nsc_fd_t *, int);
 102 static int _nsc_decode_io(nsc_def_t *, nsc_io_t *);
 103 
 104 void _nsc_release_io(nsc_io_t *);
 105 static void _nsc_free_fd(nsc_fd_t *);
 106 static void _nsc_free_iodev(nsc_iodev_t *);
 107 static void _nsc_free_dev(nsc_dev_t *);
 108 static void _nsc_free_io(nsc_io_t *);
 109 static void _nsc_relink_fd(nsc_fd_t *, nsc_fd_t **, nsc_fd_t **, nsc_iodev_t *);
 110 
 111 static int _nsc_setval(nsc_dev_t *, char *, char *, int, int);
 112 static void r_nsc_setval(ncall_t *, int *);
 113 static void r_nsc_setval_all(ncall_t *, int *);
 114 
 115 extern void _nsc_add_disk(nsc_io_t *);
 116 extern void _nsc_add_cache(nsc_io_t *);
 117 
 118 
 119 /*
 120  * void
 121  * _nsc_init_dev (void)
 122  *      Initialise device subsystem.
 123  *
 124  * Calling/Exit State:
 125  *      Called at driver initialisation time to allocate necessary
 126  *      data structures.
 127  */
 128 void
 129 _nsc_init_dev()
 130 {
 131         mutex_init(&_nsc_io_lock, NULL, MUTEX_DRIVER, NULL);
 132         mutex_init(&_nsc_devval_lock, NULL, MUTEX_DRIVER, NULL);
 133 
 134         _nsc_null_io = nsc_register_io("null", NSC_NULL, (nsc_def_t *)0);
 135 
 136         if (!_nsc_null_io)
 137                 cmn_err(CE_PANIC, "nsctl: nsc_init_dev");
 138 
 139         ncall_register_svc(NSC_SETVAL_ALL, r_nsc_setval_all);
 140         ncall_register_svc(NSC_SETVAL, r_nsc_setval);
 141 }
 142 
 143 
 144 void
 145 _nsc_deinit_dev()
 146 {
 147         nsc_devval_t *dv;
 148         nsc_val_t *vp;
 149 
 150         mutex_enter(&_nsc_devval_lock);
 151 
 152         while ((dv = _nsc_devval_top) != NULL) {
 153                 while ((vp = dv->dv_values) != NULL) {
 154                         dv->dv_values = vp->sv_next;
 155                         nsc_kmem_free(vp, sizeof (*vp));
 156                 }
 157 
 158                 _nsc_devval_top = dv->dv_next;
 159                 nsc_kmem_free(dv, sizeof (*dv));
 160         }
 161 
 162         mutex_exit(&_nsc_devval_lock);
 163 
 164         ncall_unregister_svc(NSC_SETVAL_ALL);
 165         ncall_unregister_svc(NSC_SETVAL);
 166 
 167         mutex_destroy(&_nsc_devval_lock);
 168         mutex_destroy(&_nsc_io_lock);
 169 }
 170 
 171 
 172 /*
 173  * nsc_io_t *
 174  * nsc_register_io (char *name, int type, nsc_def_t *def)
 175  *      Register an I/O module.
 176  *
 177  * Calling/Exit State:
 178  *      Returns a token for use in future calls to nsc_unregister_io.
 179  *      The ID and flags for the module are specified by 'type' and
 180  *      the appropriate entry points are defined using 'def'. If
 181  *      registration fails NULL is returned.
 182  *
 183  * Description:
 184  *      Registers an I/O module for use by subsequent calls to
 185  *      nsc_open.
 186  */
 187 nsc_io_t *
 188 nsc_register_io(name, type, def)
 189 char *name;
 190 int type;
 191 nsc_def_t *def;
 192 {
 193         nsc_io_t *io, *tp;
 194         int rc, id, flag;
 195         nsc_io_t **iop;
 196 
 197         id = (type & NSC_TYPES);
 198         flag = (type & ~NSC_TYPES);
 199 
 200         if ((!(id & NSC_ID) || (id & ~NSC_IDS)) &&
 201                         (id != NSC_NULL || _nsc_null_io))
 202                 return (NULL);
 203 
 204         if (!(io = _nsc_alloc_io(id, name, flag)))
 205                 return (NULL);
 206 
 207         rc = _nsc_decode_io(def, io);
 208 
 209         if (!rc && id != NSC_NULL) {
 210                 _nsc_free_io(io);
 211                 return (NULL);
 212         }
 213 
 214         mutex_enter(&_nsc_io_lock);
 215 
 216         for (tp = _nsc_io_top; tp; tp = tp->next) {
 217                 if (strcmp(tp->name, name) == 0 || tp->id == id) {
 218                         mutex_exit(&_nsc_io_lock);
 219                         _nsc_free_io(io);
 220                         return (NULL);
 221                 }
 222         }
 223 
 224         for (iop = &_nsc_io_top; *iop; iop = &(*iop)->next)
 225                 if (id >= (*iop)->id)
 226                         break;
 227 
 228         io->next = (*iop);
 229         (*iop) = io;
 230 
 231         _nsc_io_lbolt = nsc_lbolt();
 232 
 233         while ((rc = _nsc_reopen_io(NULL, 0)) != 0)
 234                 if (rc != ERESTART)
 235                         break;
 236 
 237         mutex_exit(&_nsc_io_lock);
 238         return (io);
 239 }
 240 
 241 
 242 /*
 243  * static int
 244  * _nsc_decode_io (nsc_def_t *def, nsc_io_t *io)
 245  *      Decode I/O module definition.
 246  *
 247  * Calling/Exit State:
 248  *      Returns TRUE if the definition contains an adequate
 249  *      description of an I/O module.
 250  *
 251  * Description:
 252  *      Decode the definition of an I/O module and supply
 253  *      translation routines where possible for operations
 254  *      that are not defined.
 255  */
 256 static int
 257 _nsc_decode_io(def, io)
 258 nsc_def_t *def;
 259 nsc_io_t *io;
 260 {
 261         nsc_decode_param(def, _nsc_io_def, (long *)io);
 262         nsc_decode_param(def, _nsc_disk_def, (long *)io);
 263         nsc_decode_param(def, _nsc_cache_def, (long *)io);
 264 
 265         _nsc_add_disk(io);
 266         _nsc_add_cache(io);
 267 
 268         return (1);
 269 }
 270 
 271 
 272 /*
 273  * int
 274  * nsc_unregister_io (nsc_io_t *io, int flag)
 275  *      Un-register an I/O module.
 276  *
 277  * Calling/Exit State:
 278  *      Returns 0 on success, otherwise returns an error code.
 279  *
 280  * Description:
 281  *      The specified I/O module is un-registered if possible.
 282  *      All open file descriptors using the module will be closed
 283  *      in preparation for a subsequent re-open.
 284  *
 285  *      If NSC_PCATCH is specified and a signal is received,
 286  *      the unregister will be terminated and EINTR returned.
 287  */
 288 int
 289 nsc_unregister_io(nsc_io_t *io, int flag)
 290 {
 291         nsc_path_t *sp;
 292         nsc_io_t *xio;
 293         int rc = 0;
 294 
 295         if (io == _nsc_null_io)
 296                 return (EINVAL);
 297 
 298         mutex_enter(&_nsc_io_lock);
 299 
 300         for (xio = _nsc_io_top; xio; xio = xio->next)
 301                 if (xio == io)
 302                         break;
 303 
 304         if (!xio || io->pend) {
 305                 mutex_exit(&_nsc_io_lock);
 306                 return (xio ? EALREADY : 0);
 307         }
 308 
 309         io->pend = 1;
 310 lp:
 311         for (sp = _nsc_path_top; sp; sp = sp->sp_next)
 312                 if (sp->sp_io == io) {
 313                         mutex_exit(&_nsc_io_lock);
 314 
 315                         if ((rc = nsc_unregister_path(sp, flag)) != 0) {
 316                                 io->pend = 0;
 317                                 return (rc);
 318                         }
 319 
 320                         mutex_enter(&_nsc_io_lock);
 321                         goto lp;
 322                 }
 323 
 324         _nsc_io_lbolt = nsc_lbolt();
 325 
 326         while (io->refcnt && !rc) {
 327                 while ((rc = _nsc_reopen_io(NULL, flag)) != 0)
 328                         if (rc != ERESTART)
 329                                 break;
 330 
 331                 if (rc || !io->refcnt)
 332                         break;
 333 
 334                 if (!cv_wait_sig(&io->cv, &_nsc_io_lock))
 335                         rc = EINTR;
 336         }
 337 
 338         /*
 339          * We have tried to get rid of all the IO provider's clients.
 340          * If there are still anonymous buffers outstanding, then fail
 341          * the unregister.
 342          */
 343 
 344         if (!rc && io->abufcnt > 0)
 345                 rc = EUSERS;
 346 
 347         if (rc)
 348                 io->pend = 0;
 349 
 350         mutex_exit(&_nsc_io_lock);
 351 
 352         if (!rc)
 353                 _nsc_free_io(io);
 354 
 355         return (rc);
 356 }
 357 
 358 
 359 /*
 360  * nsc_path_t *
 361  * nsc_register_path (char *path, int type, nsc_io_t *io)
 362  *      Register interest in pathname.
 363  *
 364  * Calling/Exit State:
 365  *      Returns a token for use in future calls to
 366  *      nsc_unregister_path. The 'path' argument can contain
 367  *      wild characters. If registration fails NULL is returned.
 368  *      May not be called for io providers that support NSC_ANON.
 369  *
 370  * Description:
 371  *      Registers an interest in any pathnames matching 'path'
 372  *      which are opened with the specified type.
 373  */
 374 nsc_path_t *
 375 nsc_register_path(char *path, int type, nsc_io_t *io)
 376 {
 377         nsc_path_t *sp, **spp;
 378         int rc;
 379 
 380         if ((type & NSC_IDS) || !io || (io->provide & NSC_ANON) ||
 381             !(sp = nsc_kmem_zalloc(sizeof (*sp), KM_SLEEP, _nsc_local_mem)))
 382                 return (NULL);
 383 
 384         sp->sp_path = nsc_strdup(path);
 385         sp->sp_type = type;
 386         sp->sp_io = io;
 387 
 388         mutex_enter(&_nsc_io_lock);
 389 
 390         for (spp = &_nsc_path_top; *spp; spp = &(*spp)->sp_next)
 391                 if (io->id >= (*spp)->sp_io->id)
 392                         break;
 393 
 394         sp->sp_next = (*spp);
 395         (*spp) = sp;
 396 
 397         _nsc_io_lbolt = nsc_lbolt();
 398 
 399         while ((rc = _nsc_reopen_io(path, 0)) != 0)
 400                 if (rc != ERESTART)
 401                         break;
 402 
 403         mutex_exit(&_nsc_io_lock);
 404         return (sp);
 405 }
 406 
 407 
 408 /*
 409  * int
 410  * nsc_unregister_path (nsc_path_t *sp, int flag)
 411  *      Un-register interest in pathname.
 412  *
 413  * Calling/Exit State:
 414  *      Returns 0 on success, otherwise returns an error code.
 415  *
 416  * Description:
 417  *      Interest in the specified pathname is un-registered
 418  *      if possible. All appropriate file descriptors will be
 419  *      closed in preparation for a subsequent re-open.
 420  *
 421  *      If NSC_PCATCH is specified and a signal is received,
 422  *      the unregister will be terminated and EINTR returned.
 423  */
 424 int
 425 nsc_unregister_path(sp, flag)
 426 nsc_path_t *sp;
 427 int flag;
 428 {
 429         nsc_path_t *xsp, **spp;
 430         int rc;
 431 
 432         mutex_enter(&_nsc_io_lock);
 433 
 434         for (xsp = _nsc_path_top; xsp; xsp = xsp->sp_next)
 435                 if (xsp == sp)
 436                         break;
 437 
 438         if (!xsp || sp->sp_pend) {
 439                 mutex_exit(&_nsc_io_lock);
 440                 return (xsp ? EALREADY : 0);
 441         }
 442 
 443         sp->sp_pend = 1;
 444         _nsc_io_lbolt = nsc_lbolt();
 445 
 446         while ((rc = _nsc_reopen_io(sp->sp_path, flag)) != 0)
 447                 if (rc != ERESTART) {
 448                         sp->sp_pend = 0;
 449                         mutex_exit(&_nsc_io_lock);
 450                         return (rc);
 451                 }
 452 
 453         for (spp = &_nsc_path_top; *spp; spp = &(*spp)->sp_next)
 454                 if (*spp == sp)
 455                         break;
 456 
 457         if (*spp)
 458                 (*spp) = sp->sp_next;
 459 
 460         mutex_exit(&_nsc_io_lock);
 461 
 462         nsc_strfree(sp->sp_path);
 463         nsc_kmem_free(sp, sizeof (*sp));
 464         return (0);
 465 }
 466 
 467 
 468 /*
 469  * static int
 470  * _nsc_reopen_io (char *path, int flag)
 471  *      Force re-open of all file descriptors.
 472  *
 473  * Calling/Exit State:
 474  *      The _nsc_io_lock must be held across calls to
 475  *      this function.
 476  *
 477  *      Returns 0 if the force succeeds without releasing
 478  *      _nsc_io_lock, otherwise returns an error code.
 479  *
 480  * Description:
 481  *      A re-open is forced for all file descriptors as
 482  *      appropriate. For performance reasons available
 483  *      devices are re-opened before those that would block.
 484  */
 485 static int
 486 _nsc_reopen_io(path, flag)
 487 char *path;
 488 int flag;
 489 {
 490         nsc_dev_t *dp, *dev;
 491         int rc, errno = 0;
 492         int try, run;
 493 
 494         for (run = 1, try = (NSC_TRY | NSC_DEFER); run--; try = 0) {
 495                 for (dev = _nsc_dev_top; dev; dev = dev->nsc_next) {
 496                         if (path && !nsc_strmatch(dev->nsc_path, path))
 497                                 continue;
 498 
 499                         if (!(rc = _nsc_reopen_dev(dev, flag | try)))
 500                                 continue;
 501 
 502                         for (dp = _nsc_dev_top; dp; dp = dp->nsc_next)
 503                                 if (dp == dev)
 504                                         break;
 505 
 506                         if (!dp)
 507                                 return (ERESTART);
 508 
 509                         if (try && !(flag & NSC_TRY))
 510                                 run = 1;
 511                         if (!run && errno != ERESTART)
 512                                 errno = rc;
 513                 }
 514         }
 515 
 516         return (errno);
 517 }
 518 
 519 
 520 /*
 521  * static int
 522  * _nsc_reopen_dev (nsc_dev_t *dev, int flag)
 523  *      Force re-open of entire device.
 524  *
 525  * Calling/Exit State:
 526  *      The _nsc_io_lock must be held across calls to
 527  *      this function.
 528  *
 529  *      Returns 0 if the force succeeds without releasing
 530  *      _nsc_io_lock, otherwise returns an error code.
 531  *
 532  * Description:
 533  *      A re-open is forced for all file descriptors for the
 534  *      device as appropriate.
 535  */
 536 static int
 537 _nsc_reopen_dev(dev, flag)
 538 nsc_dev_t *dev;
 539 int flag;
 540 {
 541         int rc, errno = 0;
 542         nsc_iodev_t *iodev;
 543         int try, run;
 544         nsc_fd_t *fd;
 545 
 546         mutex_enter(&dev->nsc_lock);
 547 
 548         for (run = 1, try = (NSC_TRY | NSC_DEFER); run--; try = 0)
 549                 for (iodev = dev->nsc_list; iodev; iodev = iodev->si_next) {
 550                         for (fd = iodev->si_open; fd; fd = fd->sf_next) {
 551                                 if (!(rc = _nsc_reopen_fd(fd, flag | try)))
 552                                         continue;
 553 
 554                                 if (rc == -ERESTART)
 555                                         return (ERESTART);
 556 
 557                                 if (!_nsc_relock_dev(dev, fd, iodev))
 558                                         return (ERESTART);
 559 
 560                                 if (try && !(flag & NSC_TRY))
 561                                         run = 1;
 562                                 if (!run && errno != ERESTART)
 563                                         errno = rc;
 564                         }
 565                 }
 566 
 567         for (run = 1, try = (NSC_TRY | NSC_DEFER); run--; try = 0)
 568                 for (fd = dev->nsc_close; fd; fd = fd->sf_next) {
 569                         if (!(rc = _nsc_reopen_fd(fd, flag | try)))
 570                                 continue;
 571 
 572                         if (rc == -ERESTART)
 573                                 return (ERESTART);
 574 
 575                         if (!_nsc_relock_dev(dev, fd, NULL))
 576                                 return (ERESTART);
 577 
 578                         if (try && !(flag & NSC_TRY))
 579                                 run = 1;
 580                         if (!run && errno != ERESTART)
 581                                 errno = rc;
 582                 }
 583 
 584         mutex_exit(&dev->nsc_lock);
 585         return (errno);
 586 }
 587 
 588 
 589 /*
 590  * static int
 591  * _nsc_relock_dev (nsc_dev_t *dev, nsc_fd_t *fd, nsc_iodev_t *iodev)
 592  *      Relock device structure if possible.
 593  *
 594  * Calling/Exit State:
 595  *      The _nsc_io_lock must be held across calls to
 596  *      this function.
 597  *
 598  *      Checks whether the file descriptor is still part
 599  *      of the specified device and I/O device. If so the
 600  *      device lock is taken. Otherwise FALSE is returned.
 601  */
 602 static int
 603 _nsc_relock_dev(nsc_dev_t *dev, nsc_fd_t *fd, nsc_iodev_t *iodev)
 604 {
 605         nsc_fd_t *fp = NULL;
 606         nsc_iodev_t *iop;
 607         nsc_dev_t *dp;
 608 
 609         for (dp = _nsc_dev_top; dp; dp = dp->nsc_next)
 610                 if (dp == dev)
 611                         break;
 612 
 613         if (!dp)
 614                 return (0);
 615 
 616         mutex_enter(&dev->nsc_lock);
 617 
 618         if (iodev)
 619                 for (iop = dev->nsc_list; iop; iop = iop->si_next)
 620                         if (iop == iodev)
 621                                 break;
 622 
 623         if (!iodev || iop) {
 624                 fp = (iodev) ? iodev->si_open : dev->nsc_close;
 625 
 626                 for (; fp; fp = fp->sf_next)
 627                         if (fp == fd)
 628                                 break;
 629         }
 630 
 631         if (!fp) {
 632                 mutex_exit(&dev->nsc_lock);
 633                 return (0);
 634         }
 635 
 636         return (1);
 637 }
 638 
 639 
 640 /*
 641  * static int
 642  * _nsc_reopen_fd (nsc_fd_t *dev, int flag)
 643  *      Force re-open of file descriptor.
 644  *
 645  * Calling/Exit State:
 646  *      Both _nsc_io_lock and the device lock must be held
 647  *      across calls to this function.
 648  *
 649  *      Returns 0 if the force succeeds without releasing
 650  *      any locks, otherwise returns an error code. If an
 651  *      error code is returned the device lock is released.
 652  *
 653  * Description:
 654  *      If appropriate the file descriptor is closed in order
 655  *      to force a subsequent open using the currently available
 656  *      resources.
 657  */
 658 static int
 659 _nsc_reopen_fd(fd, flag)
 660 nsc_fd_t *fd;
 661 int flag;
 662 {
 663         nsc_dev_t *dev = fd->sf_dev;
 664         nsc_iodev_t *iodev = fd->sf_iodev;
 665         int changed = 0;
 666         int rc;
 667 
 668         if (!fd->sf_pend && !iodev)
 669                 return (0);
 670 
 671         if (fd->sf_pend == _NSC_OPEN)
 672                 if (fd->sf_lbolt - _nsc_io_lbolt > 0)
 673                         return (0);
 674 
 675         if (iodev &&
 676             (iodev->si_io ==
 677                 _nsc_find_io(dev->nsc_path, fd->sf_type, &changed)) &&
 678             !changed)
 679                 return (0);
 680 
 681         if (iodev)
 682                 fd->sf_reopen = 1;
 683 
 684         mutex_exit(&_nsc_io_lock);
 685 
 686         dev->nsc_reopen = 1;
 687 
 688         rc = _nsc_close_fd(fd, flag);
 689 
 690         dev->nsc_reopen = 0;
 691 
 692         if (rc == EAGAIN && (flag & NSC_DEFER) && fd->sf_reopen)
 693                 dev->nsc_drop = 1;
 694 
 695         mutex_exit(&dev->nsc_lock);
 696 
 697         if (rc == -ERESTART)
 698                 delay(2);       /* allow other threads cpu time */
 699 
 700         mutex_enter(&_nsc_io_lock);
 701         return (rc ? rc : ERESTART);
 702 }
 703 
 704 
 705 /*
 706  * nsc_fd_t *
 707  * nsc_open (char *path, int type, nsc_def_t *def, blind_t arg, int *sts)
 708  *      Open file descriptor for pathname.
 709  *
 710  * Calling/Exit State:
 711  *      Returns file descriptor if open succeeds, otherwise
 712  *      returns 0 and puts error code in the location pointed
 713  *      to by sts.
 714  *
 715  * Description:
 716  *      Open the specified pathname using an appropriate access
 717  *      method.
 718  */
 719 nsc_fd_t *
 720 nsc_open(path, type, def, arg, sts)
 721 char *path;
 722 int type;
 723 nsc_def_t *def;
 724 blind_t arg;
 725 int *sts;
 726 {
 727         int flag, rc;
 728         nsc_fd_t *fd;
 729 
 730         flag = (type & ~NSC_TYPES);
 731         type &= NSC_TYPES;
 732 
 733         if ((flag & NSC_READ) == 0)
 734                 flag |= NSC_RDWR;
 735 
 736         if ((rc = _nsc_alloc_fd(path, type, flag, &fd)) != 0) {
 737                 if (sts)
 738                         *sts = rc;
 739                 return (NULL);
 740         }
 741 
 742         fd->sf_arg = arg;
 743         fd->sf_aio = _nsc_null_io;
 744 
 745         nsc_decode_param(def, _nsc_fd_def, (long *)fd);
 746 
 747         mutex_enter(&fd->sf_dev->nsc_lock);
 748 
 749         while ((rc = _nsc_open_fd(fd, flag)) != 0)
 750                 if (rc != ERESTART)
 751                         break;
 752 
 753         mutex_exit(&fd->sf_dev->nsc_lock);
 754 
 755         if (rc) {
 756                 _nsc_free_fd(fd);
 757                 if (sts)
 758                         *sts = rc;
 759                 return (NULL);
 760         }
 761 
 762         return (fd);
 763 }
 764 
 765 
 766 /*
 767  * int
 768  * _nsc_open_fd (nsc_fd_t *fd, int flag)
 769  *      Open file descriptor.
 770  *
 771  * Calling/Exit State:
 772  *      The device lock must be held across calls to
 773  *      this function.
 774  *
 775  *      Returns 0 if the open succeeds, otherwise
 776  *      returns an error code.
 777  *
 778  * Description:
 779  *      Open the specified file descriptor.
 780  */
 781 int
 782 _nsc_open_fd(fd, flag)
 783 nsc_fd_t *fd;
 784 int flag;
 785 {
 786         nsc_dev_t *dev = fd->sf_dev;
 787         int rc;
 788 
 789         if (fd->sf_pend)
 790                 return (_nsc_wait_dev(dev, flag));
 791 
 792         if (fd->sf_iodev)
 793                 return (0);
 794         if (flag & NSC_NOBLOCK)
 795                 return (EAGAIN);
 796 
 797         fd->sf_pend = _NSC_OPEN;
 798         fd->sf_lbolt = nsc_lbolt();
 799 
 800         mutex_exit(&dev->nsc_lock);
 801 
 802         rc = _nsc_open_fn(fd, flag);
 803 
 804         mutex_enter(&dev->nsc_lock);
 805         fd->sf_pend = 0;
 806 
 807         if (!rc)
 808                 fd->sf_iodev->si_pend = 0;
 809 
 810         if (dev->nsc_wait || dev->nsc_refcnt <= 0)
 811                 cv_broadcast(&dev->nsc_cv);
 812 
 813         return (rc ? rc : ERESTART);
 814 }
 815 
 816 
 817 /*
 818  * static int
 819  * _nsc_open_fn (nsc_fd_t *fd, int flag)
 820  *      Allocate I/O device and open file descriptor.
 821  *
 822  * Calling/Exit State:
 823  *      No locks may be held across this function.
 824  *
 825  *      If the open succeeds an I/O device will be
 826  *      attached to the file descriptor, marked as
 827  *      pending and 0 returned. Otherwise, returns
 828  *      an error code.
 829  *
 830  * Description:
 831  *      Allocate an I/O device and open the specified
 832  *      file descriptor.
 833  */
 834 static int
 835 _nsc_open_fn(fd, flag)
 836 nsc_fd_t *fd;
 837 int flag;
 838 {
 839         nsc_dev_t *dev = fd->sf_dev;
 840         nsc_iodev_t *iodev;
 841         int rc;
 842 
 843         if ((rc = _nsc_alloc_iodev(dev, fd->sf_type, &iodev)) != 0)
 844                 return (rc);
 845 
 846         mutex_enter(&dev->nsc_lock);
 847 
 848         if (iodev->si_pend) {
 849                 rc = _nsc_wait_dev(dev, flag);
 850                 mutex_exit(&dev->nsc_lock);
 851                 _nsc_free_iodev(iodev);
 852                 return (rc);
 853         }
 854 
 855         iodev->si_pend = _NSC_OPEN;
 856         mutex_exit(&dev->nsc_lock);
 857 
 858         rc = (*iodev->si_io->open)(dev->nsc_path,
 859                         (fd->sf_flag & ~NSC_RDWR), &fd->sf_cd, iodev);
 860 
 861         if (rc) {
 862                 iodev->si_pend = 0;
 863                 _nsc_free_iodev(iodev);
 864                 return (rc);
 865         }
 866 
 867         /* save away the DevMaj and DevMin values */
 868         if (iodev->si_io->id == NSC_RAW_ID) {
 869                 rc = _nsc_setval(dev, NULL, NSC_DEVMAJ,
 870                     (int)getmajor((dev_t)fd->sf_cd), FALSE);
 871 #ifdef DEBUG
 872                 if (rc != 1) {
 873                         cmn_err(CE_NOTE, "!nsctl: could not set DevMaj (%s:%x)",
 874                             dev->nsc_path, (int)getmajor((dev_t)fd->sf_cd));
 875                 }
 876 #endif
 877 
 878                 rc = _nsc_setval(dev, NULL, NSC_DEVMIN,
 879                     (int)getminor((dev_t)fd->sf_cd), FALSE);
 880 #ifdef DEBUG
 881                 if (rc != 1) {
 882                         cmn_err(CE_NOTE, "!nsctl: could not set DevMin (%s:%x)",
 883                             dev->nsc_path, (int)getminor((dev_t)fd->sf_cd));
 884                 }
 885 #endif
 886         }
 887 
 888         fd->sf_iodev = iodev;
 889         _nsc_relink_fd(fd, &dev->nsc_close, &iodev->si_open, iodev);
 890 
 891         return (0);
 892 }
 893 
 894 
 895 /*
 896  * int
 897  * nsc_close (nsc_fd_t *fd)
 898  *      Close file descriptor for pathname.
 899  *
 900  * Calling/Exit State:
 901  *      Returns 0 if close succeeds, otherwise returns error
 902  *      code.
 903  *
 904  * Description:
 905  *      Close the specified file descriptor. It is assumed
 906  *      that all other users of this file descriptor have
 907  *      finished. Any reserve will be discarded before the
 908  *      close is performed.
 909  */
 910 int
 911 nsc_close(fd)
 912 nsc_fd_t *fd;
 913 {
 914         int rc;
 915 
 916         if (!fd)
 917                 return (0);
 918 
 919         while (fd->sf_reserve)
 920                 nsc_release(fd);
 921 
 922         mutex_enter(&fd->sf_dev->nsc_lock);
 923 
 924         fd->sf_owner = NULL;
 925 
 926         while ((rc = _nsc_close_fd(fd, 0)) != 0)
 927                 if (rc != ERESTART)
 928                         break;
 929 
 930         nsc_decode_param(_nsc_fd_def, _nsc_fd_def, (long *)fd);
 931 
 932         mutex_exit(&fd->sf_dev->nsc_lock);
 933 
 934         if (!rc)
 935                 _nsc_free_fd(fd);
 936         return (rc);
 937 }
 938 
 939 
 940 /*
 941  * int
 942  * _nsc_close_fd (nsc_fd_t *fd, int flag)
 943  *      Close file descriptor.
 944  *
 945  * Calling/Exit State:
 946  *      The device lock must be held across calls to
 947  *      this function.
 948  *
 949  *      Returns 0 if the close succeeds, otherwise
 950  *      returns an error code.
 951  *
 952  * Description:
 953  *      Close the specified file descriptor.
 954  */
 955 int
 956 _nsc_close_fd(fd, flag)
 957 nsc_fd_t *fd;
 958 int flag;
 959 {
 960         nsc_dev_t *dev = fd->sf_dev;
 961         nsc_iodev_t *iodev;
 962         int rc;
 963 
 964         if (fd->sf_pend) {
 965                 if (fd->sf_pend == _NSC_CLOSE && dev->nsc_reopen != 0)
 966                         return (-ERESTART);
 967 
 968                 return (_nsc_wait_dev(dev, flag));
 969         }
 970 
 971         flag |= NSC_RDWR;
 972         iodev = fd->sf_iodev;
 973 
 974         if (!iodev)
 975                 return (0);
 976 
 977         if ((rc = _nsc_detach_fd(fd, flag)) != 0)
 978                 return (rc);
 979 
 980         if (iodev->si_pend)
 981                 return (_nsc_wait_dev(dev, flag));
 982 
 983         if (iodev->si_open == fd && !fd->sf_next) {
 984                 if ((rc = _nsc_detach_iodev(iodev, NULL, flag)) != 0)
 985                         return (rc);
 986 
 987                 if (dev->nsc_list == iodev && !iodev->si_next)
 988                         if ((rc = _nsc_detach_dev(dev, NULL, flag)) != 0)
 989                                 return (rc);
 990         }
 991 
 992         if (flag & NSC_NOBLOCK)
 993                 return (EAGAIN);
 994 
 995         fd->sf_pend = _NSC_CLOSE;
 996         iodev->si_pend = _NSC_CLOSE;
 997         mutex_exit(&dev->nsc_lock);
 998 
 999         rc = _nsc_close_fn(fd);
1000 
1001         mutex_enter(&dev->nsc_lock);
1002         fd->sf_pend = 0;
1003 
1004         fd->sf_reopen = 0;
1005         if (rc)
1006                 iodev->si_pend = 0;
1007 
1008         if (dev->nsc_wait || dev->nsc_refcnt <= 0)
1009                 cv_broadcast(&dev->nsc_cv);
1010 
1011         return (rc ? rc : ERESTART);
1012 }
1013 
1014 
1015 /*
1016  * static int
1017  * _nsc_close_fn (nsc_fd_t *fd)
1018  *      Close file descriptor and free I/O device.
1019  *
1020  * Calling/Exit State:
1021  *      No locks may be held across this function.
1022  *
1023  *      Returns 0 if the close succeeds, otherwise
1024  *      returns an error code.
1025  *
1026  *      If the close succeeds the I/O device will be
1027  *      detached from the file descriptor, released
1028  *      and 0 returned. Otherwise, returns an error
1029  *      code.
1030  *
1031  * Description:
1032  *      Close the specified file descriptor and free
1033  *      the I/O device.
1034  */
1035 static int
1036 _nsc_close_fn(fd)
1037 nsc_fd_t *fd;
1038 {
1039         nsc_iodev_t *iodev = fd->sf_iodev;
1040         nsc_dev_t *dev = fd->sf_dev;
1041         int last, rc;
1042 
1043         last = (iodev->si_open == fd && !fd->sf_next);
1044 
1045         if (last || (iodev->si_io->flag & NSC_REFCNT))
1046                 if ((rc = (*iodev->si_io->close)(fd->sf_cd)) != 0)
1047                         return (rc);
1048 
1049         fd->sf_iodev = NULL;
1050         _nsc_relink_fd(fd, &iodev->si_open, &dev->nsc_close, iodev);
1051 
1052         iodev->si_pend = 0;
1053         _nsc_free_iodev(iodev);
1054 
1055         return (0);
1056 }
1057 
1058 
1059 /*
1060  * void
1061  * nsc_set_owner (nsc_fd_t *fd, nsc_iodev_t *iodev)
1062  *      Set owner associated with file descriptor.
1063  *
1064  * Calling/Exit State:
1065  *      Sets the owner field in the file descriptor.
1066  */
1067 void
1068 nsc_set_owner(nsc_fd_t *fd, nsc_iodev_t *iodev)
1069 {
1070         if (fd) {
1071                 mutex_enter(&fd->sf_dev->nsc_lock);
1072                 fd->sf_owner = iodev;
1073                 mutex_exit(&fd->sf_dev->nsc_lock);
1074         }
1075 }
1076 
1077 
1078 /*
1079  * char *
1080  * nsc_pathname (nsc_fd_t *fd)
1081  *      Pathname associated with file descriptor.
1082  *
1083  * Calling/Exit State:
1084  *      Returns a pointer to the pathname associated
1085  *      with the given file descriptor.
1086  */
1087 char *
1088 nsc_pathname(fd)
1089 nsc_fd_t *fd;
1090 {
1091         return ((fd) ? (fd->sf_dev->nsc_path) : 0);
1092 }
1093 
1094 
1095 /*
1096  * int
1097  * nsc_fdpathcmp(nsc_fd_t *fd, uint64_t phash, char *path)
1098  *      Compare fd to pathname and hash
1099  *
1100  * Calling/Exit State:
1101  *      Returns comparison value like strcmp(3C).
1102  *
1103  * Description:
1104  *      Does an optimised comparison of the pathname and associated hash
1105  *      value (as returned from nsc_strhash()) against the pathname of
1106  *      the filedescriptor, fd.
1107  */
1108 int
1109 nsc_fdpathcmp(nsc_fd_t *fd, uint64_t phash, char *path)
1110 {
1111         int rc = -1;
1112 
1113         if (fd != NULL && fd->sf_dev->nsc_phash == phash)
1114                 rc = strcmp(fd->sf_dev->nsc_path, path);
1115 
1116         return (rc);
1117 }
1118 
1119 
1120 static int
1121 _nsc_setval(nsc_dev_t *dev, char *path, char *name, int val, int do_ncall)
1122 {
1123         nsc_devval_t *dv;
1124         nsc_rval_t *rval;
1125         ncall_t *ncall;
1126         nsc_val_t *vp;
1127         uint64_t phash;
1128         char *pp;
1129         int rc;
1130 
1131         ASSERT(dev != NULL || path != NULL);
1132 #ifdef DEBUG
1133         if (dev != NULL && path != NULL) {
1134                 ASSERT(strcmp(dev->nsc_path, path) == 0);
1135         }
1136 #endif
1137 
1138         pp = (dev != NULL) ? dev->nsc_path : path;
1139 
1140         if (strlen(name) >= NSC_SETVAL_MAX) {
1141 #ifdef DEBUG
1142                 cmn_err(CE_WARN, "!nsc_setval: max name size(%d) exceeded(%d)",
1143                     NSC_SETVAL_MAX-1, (int)strlen(name));
1144 #endif
1145                 return (0);
1146         }
1147 
1148         phash = nsc_strhash(pp);
1149 
1150         mutex_enter(&_nsc_devval_lock);
1151 
1152         if (dev != NULL)
1153                 dv = dev->nsc_values;
1154         else {
1155                 for (dv = _nsc_devval_top; dv != NULL; dv = dv->dv_next) {
1156                         if (phash == dv->dv_phash &&
1157                             strcmp(pp, dv->dv_path) == 0)
1158                                 /* found dv for device */
1159                                 break;
1160                 }
1161         }
1162 
1163         if (dv == NULL) {
1164                 dv = nsc_kmem_zalloc(sizeof (*dv), KM_SLEEP, _nsc_local_mem);
1165                 if (dv == NULL) {
1166                         mutex_exit(&_nsc_devval_lock);
1167                         return (0);
1168                 }
1169 
1170                 (void) strncpy(dv->dv_path, pp, sizeof (dv->dv_path));
1171                 dv->dv_phash = phash;
1172 
1173                 dv->dv_next = _nsc_devval_top;
1174                 _nsc_devval_top = dv;
1175                 if (dev != NULL)
1176                         dev->nsc_values = dv;
1177         }
1178 
1179         for (vp = dv->dv_values; vp; vp = vp->sv_next) {
1180                 if (strcmp(vp->sv_name, name) == 0) {
1181                         vp->sv_value = val;
1182                         break;
1183                 }
1184         }
1185 
1186         if (vp == NULL) {
1187                 vp = nsc_kmem_zalloc(sizeof (*vp), KM_SLEEP, _nsc_local_mem);
1188                 if (vp != NULL) {
1189                         (void) strncpy(vp->sv_name, name, sizeof (vp->sv_name));
1190                         vp->sv_value = val;
1191                         vp->sv_next = dv->dv_values;
1192                         dv->dv_values = vp;
1193                 }
1194         }
1195 
1196         mutex_exit(&_nsc_devval_lock);
1197 
1198         /*
1199          * phoenix: ncall the new value to the other node now.
1200          */
1201 
1202         if (vp && do_ncall) {
1203                 /* CONSTCOND */
1204                 ASSERT(sizeof (nsc_rval_t) <= NCALL_DATA_SZ);
1205 
1206                 rval = nsc_kmem_zalloc(sizeof (*rval), KM_SLEEP,
1207                     _nsc_local_mem);
1208                 if (rval == NULL) {
1209                         goto out;
1210                 }
1211 
1212                 rc = ncall_alloc(ncall_mirror(ncall_self()), 0, 0, &ncall);
1213                 if (rc == 0) {
1214                         (void) strncpy(rval->path, pp, sizeof (rval->path));
1215                         (void) strncpy(rval->name, name, sizeof (rval->name));
1216                         rval->value = val;
1217 
1218                         rc = ncall_put_data(ncall, rval, sizeof (*rval));
1219                         if (rc == 0) {
1220                                 /*
1221                                  * Send synchronously and read a reply
1222                                  * so that we know that the remote
1223                                  * setval has completed before this
1224                                  * function returns and hence whilst
1225                                  * the device is still reserved on this
1226                                  * node.
1227                                  */
1228                                 if (ncall_send(ncall, 0, NSC_SETVAL) == 0)
1229                                         (void) ncall_read_reply(ncall, 1, &rc);
1230                         }
1231 
1232                         ncall_free(ncall);
1233                 }
1234 
1235                 nsc_kmem_free(rval, sizeof (*rval));
1236         }
1237 
1238 out:
1239         return (vp ? 1 : 0);
1240 }
1241 
1242 
1243 /* ARGSUSED */
1244 
1245 static void
1246 r_nsc_setval(ncall_t *ncall, int *ap)
1247 {
1248         nsc_rval_t *rval;
1249         int rc;
1250 
1251         rval = nsc_kmem_zalloc(sizeof (*rval), KM_SLEEP, _nsc_local_mem);
1252         if (rval == NULL) {
1253                 ncall_reply(ncall, ENOMEM);
1254                 return;
1255         }
1256 
1257         rc = ncall_get_data(ncall, rval, sizeof (*rval));
1258         if (rc != 0) {
1259                 ncall_reply(ncall, EFAULT);
1260                 return;
1261         }
1262 
1263         if (_nsc_setval(NULL, rval->path, rval->name, rval->value, FALSE))
1264                 rc = 0;
1265         else
1266                 rc = ENOMEM;
1267 
1268         ncall_reply(ncall, rc);
1269         nsc_kmem_free(rval, sizeof (*rval));
1270 }
1271 
1272 
1273 /* ARGSUSED */
1274 
1275 static void
1276 r_nsc_setval_all(ncall_t *ncall, int *ap)
1277 {
1278         nsc_rval_t *in = NULL, *out = NULL;
1279         nsc_devval_t *dv;
1280         nsc_val_t *vp;
1281         ncall_t *np;
1282         uint64_t phash;
1283         int rc;
1284 
1285         /* CONSTCOND */
1286         ASSERT(sizeof (nsc_rval_t) <= NCALL_DATA_SZ);
1287 
1288         in = nsc_kmem_zalloc(sizeof (*in), KM_SLEEP, _nsc_local_mem);
1289         out = nsc_kmem_zalloc(sizeof (*out), KM_SLEEP, _nsc_local_mem);
1290         if (in == NULL || out == NULL) {
1291                 if (in != NULL) {
1292                         nsc_kmem_free(in, sizeof (*in));
1293                         in = NULL;
1294                 }
1295                 if (out != NULL) {
1296                         nsc_kmem_free(out, sizeof (*out));
1297                         out = NULL;
1298                 }
1299                 ncall_reply(ncall, ENOMEM);
1300         }
1301 
1302         rc = ncall_get_data(ncall, in, sizeof (*in));
1303         if (rc != 0) {
1304                 ncall_reply(ncall, EFAULT);
1305                 return;
1306         }
1307 
1308         phash = nsc_strhash(in->path);
1309 
1310         (void) strncpy(out->path, in->path, sizeof (out->path));
1311 
1312         rc = ncall_alloc(ncall_mirror(ncall_self()), 0, 0, &np);
1313         if (rc != 0) {
1314                 ncall_reply(ncall, ENOMEM);
1315                 return;
1316         }
1317 
1318         mutex_enter(&_nsc_devval_lock);
1319 
1320         for (dv = _nsc_devval_top; dv; dv = dv->dv_next) {
1321                 if (dv->dv_phash == phash &&
1322                     strcmp(dv->dv_path, in->path) == 0)
1323                         break;
1324         }
1325 
1326         if (dv) {
1327                 for (vp = dv->dv_values; vp; vp = vp->sv_next) {
1328                         if (strcmp(vp->sv_name, NSC_DEVMIN) == 0 ||
1329                             strcmp(vp->sv_name, NSC_DEVMAJ) == 0) {
1330                                 /* ignore the implicit DevMin/DevMaj values */
1331                                 continue;
1332                         }
1333 
1334                         (void) strncpy(out->name, vp->sv_name,
1335                             sizeof (out->name));
1336                         out->value = vp->sv_value;
1337 
1338                         rc = ncall_put_data(np, out, sizeof (*out));
1339                         if (rc == 0) {
1340                                 /*
1341                                  * Send synchronously and read a reply
1342                                  * so that we know that the remote
1343                                  * setval has completed before this
1344                                  * function returns.
1345                                  */
1346                                 if (ncall_send(np, 0, NSC_SETVAL) == 0)
1347                                         (void) ncall_read_reply(np, 1, &rc);
1348                         }
1349 
1350                         ncall_reset(np);
1351                 }
1352 
1353                 ncall_free(np);
1354                 rc = 0;
1355         } else {
1356                 rc = ENODEV;
1357         }
1358 
1359         mutex_exit(&_nsc_devval_lock);
1360 
1361         ncall_reply(ncall, rc);
1362 
1363         nsc_kmem_free(out, sizeof (*out));
1364         nsc_kmem_free(in, sizeof (*in));
1365 }
1366 
1367 
1368 /*
1369  * int
1370  * nsc_setval (nsc_fd_t *fd, char *name, int val)
1371  *      Set value for device.
1372  *
1373  * Calling/Exit State:
1374  *      Returns 1 if the value has been set, otherwise 0.
1375  *      Must be called with the fd reserved.
1376  *
1377  * Description:
1378  *      Sets the specified global variable for the device
1379  *      to the value provided.
1380  */
1381 int
1382 nsc_setval(nsc_fd_t *fd, char *name, int val)
1383 {
1384         if (!fd)
1385                 return (0);
1386 
1387         if (!nsc_held(fd))
1388                 return (0);
1389 
1390         return (_nsc_setval(fd->sf_dev, NULL, name, val, TRUE));
1391 }
1392 
1393 
1394 /*
1395  * int
1396  * nsc_getval (nsc_fd_t *fd, char *name, int *vp)
1397  *      Get value from device.
1398  *
1399  * Calling/Exit State:
1400  *      Returns 1 if the value has been found, otherwise 0.
1401  *      Must be called with the fd reserved, except for "DevMaj" / "DevMin".
1402  *
1403  * Description:
1404  *      Finds the value of the specified device variable for
1405  *      the device and returns it in the location pointed to
1406  *      by vp.
1407  */
1408 int
1409 nsc_getval(nsc_fd_t *fd, char *name, int *vp)
1410 {
1411         nsc_devval_t *dv;
1412         nsc_val_t *val;
1413 
1414         if (!fd)
1415                 return (0);
1416 
1417         /*
1418          * Don't check for nsc_held() for the device number values
1419          * since these are magically created and cannot change when
1420          * the fd is not reserved.
1421          */
1422 
1423         if (strcmp(name, NSC_DEVMAJ) != 0 &&
1424             strcmp(name, NSC_DEVMIN) != 0 &&
1425             !nsc_held(fd))
1426                 return (0);
1427 
1428         mutex_enter(&_nsc_devval_lock);
1429 
1430         dv = fd->sf_dev->nsc_values;
1431         val = NULL;
1432 
1433         if (dv != NULL) {
1434                 for (val = dv->dv_values; val; val = val->sv_next) {
1435                         if (strcmp(val->sv_name, name) == 0) {
1436                                 *vp = val->sv_value;
1437                                 break;
1438                         }
1439                 }
1440         }
1441 
1442         mutex_exit(&_nsc_devval_lock);
1443 
1444         return (val ? 1 : 0);
1445 }
1446 
1447 
1448 /*
1449  * char *
1450  * nsc_shared (nsc_fd_t *fd)
1451  *      Device is currently shared.
1452  *
1453  * Calling/Exit State:
1454  *      The device lock must be held across calls to this
1455  *      this function.
1456  *
1457  *      Returns an indication of whether the device accessed
1458  *      by the file descriptor is currently referenced by more
1459  *      than one user.
1460  *
1461  *      This is only intended for use in performance critical
1462  *      situations.
1463  */
1464 int
1465 nsc_shared(fd)
1466 nsc_fd_t *fd;
1467 {
1468         nsc_iodev_t *iodev;
1469         int cnt = 0;
1470 
1471         if (!fd)
1472                 return (0);
1473         if (!fd->sf_iodev)
1474                 return (1);
1475 
1476         for (iodev = fd->sf_dev->nsc_list; iodev; iodev = iodev->si_next)
1477                 for (fd = iodev->si_open; fd; fd = fd->sf_next)
1478                         if (!fd->sf_owner && cnt++)
1479                                 return (1);
1480 
1481         return (0);
1482 }
1483 
1484 
1485 /*
1486  * kmutex_t *
1487  * nsc_lock_addr (nsc_fd_t *fd)
1488  *      Address of device lock.
1489  *
1490  * Calling/Exit State:
1491  *      Returns a pointer to the spin lock associated with the
1492  *      device.
1493  *
1494  * Description:
1495  *      This is only intended for use in performance critical
1496  *      situations in conjunction with nsc_reserve_lk.
1497  */
1498 kmutex_t *
1499 nsc_lock_addr(fd)
1500 nsc_fd_t *fd;
1501 {
1502         return (&fd->sf_dev->nsc_lock);
1503 }
1504 
1505 
1506 /*
1507  * int
1508  * _nsc_call_io (long f, blind_t a, blind_t b, blind_t c)
1509  *      Call information function.
1510  *
1511  * Calling/Exit State:
1512  *      Returns result from function or 0 if not available.
1513  *      f represents the offset into the I/O structure at which
1514  *      the required function can be found and a, b, c are the
1515  *      desired arguments.
1516  *
1517  * Description:
1518  *      Calls the requested function for the first available
1519  *      cache interface.
1520  */
1521 int
1522 _nsc_call_io(long f, blind_t a, blind_t b, blind_t c)
1523 {
1524         nsc_io_t *io;
1525         int (*fn)();
1526         int rc;
1527 
1528         io = _nsc_reserve_io(NULL, NSC_SDBC_ID);
1529         if (!io)
1530                 io = _nsc_reserve_io(NULL, NSC_NULL);
1531 
1532         fn = (blindfn_t)(((long *)io)[f]);
1533         rc = (*fn)(a, b, c);
1534 
1535         _nsc_release_io(io);
1536         return (rc);
1537 }
1538 
1539 
1540 /*
1541  * nsc_io_t *
1542  * _nsc_reserve_io (char *, int type)
1543  *      Reserve I/O module.
1544  *
1545  * Calling/Exit State:
1546  *      Returns address of I/O structure matching specified
1547  *      type, or NULL.
1548  *
1549  * Description:
1550  *      Searches for an appropriate I/O module and increments
1551  *      the reference count to prevent it being unregistered.
1552  */
1553 nsc_io_t *
1554 _nsc_reserve_io(path, type)
1555 char *path;
1556 int type;
1557 {
1558         nsc_io_t *io;
1559 
1560         mutex_enter(&_nsc_io_lock);
1561 
1562         if ((io = _nsc_find_io(path, type, NULL)) != 0)
1563                 io->refcnt++;
1564 
1565         mutex_exit(&_nsc_io_lock);
1566         return (io);
1567 }
1568 
1569 
1570 /*
1571  * static nsc_io_t *
1572  * _nsc_find_io (char *path, int type, int *changed)
1573  *      Find I/O module.
1574  *
1575  * Calling/Exit State:
1576  *      The _nsc_io_lock must be held across calls to
1577  *      this function.
1578  *
1579  *      Returns address of I/O structure matching specified
1580  *      type, or NULL.
1581  *
1582  *      'changed' will be set to non-zero if there is a pending
1583  *      nsc_path_t that matches the criteria for the requested type.
1584  *      This allows nsctl to distinguish between multiple
1585  *      nsc_register_path's done by the same I/O provider.
1586  *
1587  * Description:
1588  *      Searches for an appropriate I/O module.
1589  *
1590  *      1.  If <type> is a single module id find the specified I/O
1591  *          module by module id.
1592  *
1593  *      2.  Find the highest module that provides any of the I/O types
1594  *          included in <type>, taking into account any modules
1595  *          registered via the nsc_register_path() interface if <path>
1596  *          is non-NULL.
1597  *
1598  *      3.  Find an I/O module following the rules in (2), but whose
1599  *          module id is less than the id OR'd into <type>.
1600  *
1601  *      If no module is found by the above algorithms and NSC_NULL was
1602  *      included in <type>, return the _nsc_null_io module. Otherwise
1603  *      return NULL.
1604  */
1605 static nsc_io_t *
1606 _nsc_find_io(char *path, int type, int *changed)
1607 {
1608         nsc_path_t *sp = NULL;
1609         nsc_path_t *pp = NULL;
1610         nsc_io_t *io;
1611 
1612         type &= NSC_TYPES;
1613 
1614         if (path) {
1615                 for (sp = _nsc_path_top; sp; sp = sp->sp_next) {
1616                         if ((type & NSC_ID) &&
1617                             sp->sp_io->id >= (type & NSC_IDS))
1618                                 continue;
1619 
1620                         if (sp->sp_pend || (type & sp->sp_type) == 0)
1621                                 continue;
1622 
1623                         if (nsc_strmatch(path, sp->sp_path))
1624                                 break;
1625                 }
1626 
1627                 if (sp) {
1628                         /* look for matching pending paths */
1629                         for (pp = _nsc_path_top; pp; pp = pp->sp_next) {
1630                                 if (pp->sp_pend &&
1631                                     (type & pp->sp_type) &&
1632                                     nsc_strmatch(path, pp->sp_path)) {
1633                                         break;
1634                                 }
1635                         }
1636                 }
1637         }
1638 
1639         for (io = _nsc_io_top; io; io = io->next) {
1640                 if (io->pend)
1641                         continue;
1642 
1643                 if (type & NSC_ID) {
1644                         if ((type & ~NSC_IDS) == 0) {
1645                                 if (io->id == type)
1646                                         break;
1647                                 continue;
1648                         }
1649 
1650                         if (io->id >= (type & NSC_IDS))
1651                                 continue;
1652                 }
1653 
1654                 if (io->provide & type)
1655                         break;
1656         }
1657 
1658         if (pp && (!io || pp->sp_io->id >= io->id)) {
1659                 /*
1660                  * Mark this as a path change.
1661                  */
1662                 if (changed) {
1663                         *changed = 1;
1664                 }
1665         }
1666 
1667         if (sp && (!io || sp->sp_io->id >= io->id))
1668                 io = sp->sp_io;
1669 
1670         if (!io && !(type & NSC_NULL))
1671                 return (NULL);
1672 
1673         if (!io)
1674                 io = _nsc_null_io;
1675 
1676         return (io);
1677 }
1678 
1679 
1680 /*
1681  * void
1682  * _nsc_release_io (nsc_io_t *)
1683  *      Release I/O module.
1684  *
1685  * Description:
1686  *      Releases reference to I/O structure and wakes up
1687  *      anybody waiting on it.
1688  */
1689 void
1690 _nsc_release_io(io)
1691 nsc_io_t *io;
1692 {
1693         mutex_enter(&_nsc_io_lock);
1694 
1695         io->refcnt--;
1696         cv_broadcast(&io->cv);
1697 
1698         mutex_exit(&_nsc_io_lock);
1699 }
1700 
1701 
1702 /*
1703  * static int
1704  * _nsc_alloc_fd (char *path, int type, int flag, nsc_fd_t **fdp)
1705  *      Allocate file descriptor structure.
1706  *
1707  * Calling/Exit State:
1708  *      Stores address of file descriptor through fdp and
1709  *      returns 0 on success, otherwise returns error code.
1710  *
1711  * Description:
1712  *      A new file descriptor is allocated and linked in to
1713  *      the file descriptor chain which is protected by the
1714  *      device lock.
1715  *
1716  *      On return the file descriptor must contain all the
1717  *      information necessary to perform an open. Details
1718  *      specific to user callbacks are not required yet.
1719  */
1720 static int
1721 _nsc_alloc_fd(path, type, flag, fdp)
1722 char *path;
1723 int type, flag;
1724 nsc_fd_t **fdp;
1725 {
1726         nsc_dev_t *dev;
1727         nsc_fd_t *fd;
1728         int rc;
1729 
1730         if (!(fd = (nsc_fd_t *)nsc_kmem_zalloc(
1731                                 sizeof (*fd), KM_SLEEP, _nsc_local_mem)))
1732                 return (ENOMEM);
1733 
1734         if ((rc = _nsc_alloc_dev(path, &dev)) != 0) {
1735                 nsc_kmem_free(fd, sizeof (*fd));
1736                 return (rc);
1737         }
1738 
1739         mutex_enter(&dev->nsc_lock);
1740 
1741         fd->sf_type = type;
1742         fd->sf_flag = flag;
1743         fd->sf_dev = dev;
1744         fd->sf_next = dev->nsc_close;
1745         dev->nsc_close = fd;
1746 
1747         mutex_exit(&dev->nsc_lock);
1748 
1749         *fdp = fd;
1750         return (0);
1751 }
1752 
1753 
1754 /*
1755  * static int
1756  * _nsc_free_fd (nsc_fd_t *)
1757  *      Free file descriptor.
1758  *
1759  * Description:
1760  *      The file descriptor is removed from the chain and free'd
1761  *      once pending activity has completed.
1762  */
1763 static void
1764 _nsc_free_fd(fd)
1765 nsc_fd_t *fd;
1766 {
1767         nsc_dev_t *dev = fd->sf_dev;
1768         nsc_fd_t **fdp;
1769 
1770         if (!fd)
1771                 return;
1772 
1773         mutex_enter(&dev->nsc_lock);
1774 
1775         for (fdp = &dev->nsc_close; *fdp; fdp = &(*fdp)->sf_next)
1776                 if (*fdp == fd) {
1777                         *fdp = fd->sf_next;
1778                         break;
1779                 }
1780 
1781         if (dev->nsc_wait || dev->nsc_refcnt <= 0)
1782                 cv_broadcast(&dev->nsc_cv);
1783 
1784         while (fd->sf_pend)
1785                 (void) _nsc_wait_dev(dev, 0);
1786 
1787         mutex_exit(&dev->nsc_lock);
1788 
1789         _nsc_free_dev(dev);
1790 
1791         nsc_kmem_free(fd, sizeof (*fd));
1792 }
1793 
1794 
1795 /*
1796  * static void
1797  * _nsc_relink_fd (nsc_fd_t *fd, nsc_fd_t **from,
1798  *                              nsc_fd_t **to, nsc_iodev_t *iodev)
1799  *      Relink file descriptor.
1800  *
1801  * Description:
1802  *      Remove the file descriptor from the 'from' chain and
1803  *      add it to the 'to' chain. The busy flag in iodev is
1804  *      used to prevent modifications to the chain whilst a
1805  *      callback is in progress.
1806  */
1807 static void
1808 _nsc_relink_fd(nsc_fd_t *fd, nsc_fd_t **from, nsc_fd_t **to, nsc_iodev_t *iodev)
1809 {
1810         nsc_dev_t *dev = fd->sf_dev;
1811         nsc_fd_t **fdp;
1812 
1813         mutex_enter(&dev->nsc_lock);
1814 
1815         while (iodev->si_busy)
1816                 (void) _nsc_wait_dev(dev, 0);
1817 
1818         for (fdp = from; *fdp; fdp = &(*fdp)->sf_next)
1819                 if (*fdp == fd) {
1820                         *fdp = fd->sf_next;
1821                         break;
1822                 }
1823 
1824         fd->sf_next = (*to);
1825         (*to) = fd;
1826 
1827         mutex_exit(&dev->nsc_lock);
1828 }
1829 
1830 
1831 /*
1832  * static int
1833  * _nsc_alloc_iodev (nsc_dev_t *dev, int type, nsc_iodev_t **iodevp)
1834  *      Allocate I/O device structure.
1835  *
1836  * Calling/Exit State:
1837  *      Stores address of I/O device structure through iodevp
1838  *      and returns 0 on success, otherwise returns error code.
1839  *
1840  * Description:
1841  *      If an entry for the I/O device already exists increment
1842  *      the reference count and return the address, otherwise
1843  *      allocate a new structure.
1844  *
1845  *      A new structure is allocated before scanning the chain
1846  *      to avoid calling the memory allocator with a spin lock
1847  *      held. If an entry is found the new structure is free'd.
1848  *
1849  *      The I/O device chain is protected by the device lock.
1850  */
1851 static int
1852 _nsc_alloc_iodev(dev, type, iodevp)
1853 nsc_dev_t *dev;
1854 int type;
1855 nsc_iodev_t **iodevp;
1856 {
1857         nsc_iodev_t *iodev, *ip;
1858         nsc_io_t *io;
1859 
1860         if (!(iodev = (nsc_iodev_t *)nsc_kmem_zalloc(
1861                                 sizeof (*iodev), KM_SLEEP, _nsc_local_mem)))
1862                 return (ENOMEM);
1863 
1864         mutex_init(&iodev->si_lock, NULL, MUTEX_DRIVER, NULL);
1865         cv_init(&iodev->si_cv, NULL, CV_DRIVER, NULL);
1866 
1867         if (!(io = _nsc_reserve_io(dev->nsc_path, type))) {
1868                 mutex_destroy(&iodev->si_lock);
1869                 cv_destroy(&iodev->si_cv);
1870                 nsc_kmem_free(iodev, sizeof (*iodev));
1871                 return (ENXIO);
1872         }
1873 
1874         iodev->si_refcnt++;
1875         iodev->si_io = io;
1876         iodev->si_dev = dev;
1877 
1878         mutex_enter(&_nsc_io_lock);
1879         dev->nsc_refcnt++;
1880         mutex_exit(&_nsc_io_lock);
1881 
1882         mutex_enter(&dev->nsc_lock);
1883 
1884         for (ip = dev->nsc_list; ip; ip = ip->si_next)
1885                 if (ip->si_io == io) {
1886                         ip->si_refcnt++;
1887                         break;
1888                 }
1889 
1890         if (!ip) {
1891                 iodev->si_next = dev->nsc_list;
1892                 dev->nsc_list = iodev;
1893         }
1894 
1895         mutex_exit(&dev->nsc_lock);
1896 
1897         if (ip) {
1898                 _nsc_free_iodev(iodev);
1899                 iodev = ip;
1900         }
1901 
1902         *iodevp = iodev;
1903         return (0);
1904 }
1905 
1906 
1907 /*
1908  * static int
1909  * _nsc_free_iodev (nsc_iodev_t *iodev)
1910  *      Free I/O device structure.
1911  *
1912  * Description:
1913  *      Decrements the reference count of a previously allocated
1914  *      I/O device structure. If this is the last reference it
1915  *      is removed from the device chain and free'd once pending
1916  *      activity has completed.
1917  */
1918 static void
1919 _nsc_free_iodev(nsc_iodev_t *iodev)
1920 {
1921         nsc_iodev_t **ipp;
1922         nsc_dev_t *dev;
1923 
1924         if (!iodev)
1925                 return;
1926 
1927         dev = iodev->si_dev;
1928 
1929         mutex_enter(&dev->nsc_lock);
1930 
1931         if (--iodev->si_refcnt > 0) {
1932                 mutex_exit(&dev->nsc_lock);
1933                 return;
1934         }
1935 
1936         for (ipp = &dev->nsc_list; *ipp; ipp = &(*ipp)->si_next)
1937                 if (*ipp == iodev) {
1938                         *ipp = iodev->si_next;
1939                         break;
1940                 }
1941 
1942         if (dev->nsc_wait || dev->nsc_refcnt <= 0)
1943                 cv_broadcast(&dev->nsc_cv);
1944 
1945         while (iodev->si_pend || iodev->si_rpend || iodev->si_busy)
1946                 (void) _nsc_wait_dev(dev, 0);
1947 
1948         mutex_exit(&dev->nsc_lock);
1949 
1950         _nsc_release_io(iodev->si_io);
1951         _nsc_free_dev(dev);
1952 
1953         mutex_destroy(&iodev->si_lock);
1954         cv_destroy(&iodev->si_cv);
1955 
1956         nsc_kmem_free(iodev, sizeof (*iodev));
1957 }
1958 
1959 
1960 /*
1961  * static int
1962  * _nsc_alloc_dev (char *path, nsc_dev_t **devp)
1963  *      Allocate device structure.
1964  *
1965  * Calling/Exit State:
1966  *      Stores address of device structure through devp
1967  *      and returns 0 on success, otherwise returns error
1968  *      code.
1969  *
1970  * Description:
1971  *      If an entry for the device already exists increment
1972  *      the reference count and return the address, otherwise
1973  *      allocate a new structure.
1974  *
1975  *      A new structure is allocated before scanning the device
1976  *      chain to avoid calling the memory allocator with a spin
1977  *      lock held. If the device is found the new structure is
1978  *      free'd.
1979  *
1980  *      The device chain is protected by _nsc_io_lock.
1981  */
1982 static int
1983 _nsc_alloc_dev(char *path, nsc_dev_t **devp)
1984 {
1985         nsc_dev_t *dev, *dp, **ddp;
1986         nsc_devval_t *dv;
1987         nsc_rval_t *rval;
1988         ncall_t *ncall;
1989         int rc;
1990 
1991         if (!(dev = (nsc_dev_t *)nsc_kmem_zalloc(
1992             sizeof (*dev), KM_SLEEP, _nsc_local_mem)))
1993                 return (ENOMEM);
1994 
1995         dev->nsc_refcnt++;
1996 
1997         mutex_init(&dev->nsc_lock, NULL, MUTEX_DRIVER, NULL);
1998         cv_init(&dev->nsc_cv, NULL, CV_DRIVER, NULL);
1999 
2000         dev->nsc_phash = nsc_strhash(path);
2001         dev->nsc_path = nsc_strdup(path);
2002 
2003         mutex_enter(&_nsc_io_lock);
2004 
2005         dev->nsc_next = _nsc_dev_pend;
2006         _nsc_dev_pend = dev;
2007 
2008         mutex_exit(&_nsc_io_lock);
2009 
2010         mutex_enter(&_nsc_io_lock);
2011 
2012         for (dp = _nsc_dev_top; dp; dp = dp->nsc_next)
2013                 if (dp->nsc_phash == dev->nsc_phash &&
2014                     strcmp(dp->nsc_path, dev->nsc_path) == 0) {
2015                         dp->nsc_refcnt++;
2016                         break;
2017                 }
2018 
2019         if (!dp) {
2020                 for (ddp = &_nsc_dev_pend; *ddp; ddp = &(*ddp)->nsc_next)
2021                         if (*ddp == dev) {
2022                                 *ddp = dev->nsc_next;
2023                                 break;
2024                         }
2025 
2026                 dev->nsc_next = _nsc_dev_top;
2027                 _nsc_dev_top = dev;
2028         }
2029 
2030         mutex_exit(&_nsc_io_lock);
2031 
2032         if (dp) {
2033                 _nsc_free_dev(dev);
2034                 dev = dp;
2035         }
2036 
2037         /*
2038          * Try and find the device/values header for this device
2039          * and link it back to the device structure.
2040          */
2041 
2042         mutex_enter(&_nsc_devval_lock);
2043 
2044         if (dev->nsc_values == NULL) {
2045                 for (dv = _nsc_devval_top; dv; dv = dv->dv_next) {
2046                         if (dv->dv_phash == dev->nsc_phash &&
2047                             strcmp(dv->dv_path, dev->nsc_path) == 0) {
2048                                 dev->nsc_values = dv;
2049                                 break;
2050                         }
2051                 }
2052         }
2053 
2054         mutex_exit(&_nsc_devval_lock);
2055 
2056         /*
2057          * Refresh the device/values from the other node
2058          */
2059 
2060         rval = nsc_kmem_zalloc(sizeof (*rval), KM_SLEEP, _nsc_local_mem);
2061         if (rval == NULL) {
2062                 goto out;
2063         }
2064 
2065         rc = ncall_alloc(ncall_mirror(ncall_self()), 0, 0, &ncall);
2066         if (rc == 0) {
2067                 (void) strncpy(rval->path, path, sizeof (rval->path));
2068 
2069                 rc = ncall_put_data(ncall, rval, sizeof (*rval));
2070                 if (rc == 0) {
2071                         /*
2072                          * Send synchronously and read a reply
2073                          * so that we know that the updates
2074                          * have completed before this
2075                          * function returns.
2076                          */
2077                         if (ncall_send(ncall, 0, NSC_SETVAL_ALL) == 0)
2078                                 (void) ncall_read_reply(ncall, 1, &rc);
2079                 }
2080 
2081                 ncall_free(ncall);
2082         }
2083 
2084         nsc_kmem_free(rval, sizeof (*rval));
2085 
2086 out:
2087         *devp = dev;
2088         return (0);
2089 }
2090 
2091 
2092 /*
2093  * static void
2094  * _nsc_free_dev (nsc_dev_t *dev)
2095  *      Free device structure.
2096  *
2097  * Description:
2098  *      Decrements the reference count of a previously allocated
2099  *      device structure. If this is the last reference it is
2100  *      removed from the device chain and free'd once pending
2101  *      activity has completed.
2102  *
2103  *      Whilst waiting for pending activity to cease the device is
2104  *      relinked onto the pending chain.
2105  */
2106 static void
2107 _nsc_free_dev(dev)
2108 nsc_dev_t *dev;
2109 {
2110         nsc_dev_t **ddp;
2111 
2112         if (!dev)
2113                 return;
2114 
2115         mutex_enter(&_nsc_io_lock);
2116 
2117         if (--dev->nsc_refcnt > 0) {
2118                 mutex_exit(&_nsc_io_lock);
2119                 return;
2120         }
2121 
2122         for (ddp = &_nsc_dev_top; *ddp; ddp = &(*ddp)->nsc_next)
2123                 if (*ddp == dev) {
2124                         *ddp = dev->nsc_next;
2125                         dev->nsc_next = _nsc_dev_pend;
2126                         _nsc_dev_pend = dev;
2127                         break;
2128                 }
2129 
2130         mutex_exit(&_nsc_io_lock);
2131 
2132         mutex_enter(&dev->nsc_lock);
2133 
2134         while (dev->nsc_pend || dev->nsc_rpend || dev->nsc_wait) {
2135                 cv_wait(&dev->nsc_cv, &dev->nsc_lock);
2136         }
2137 
2138         mutex_exit(&dev->nsc_lock);
2139 
2140         mutex_enter(&_nsc_io_lock);
2141 
2142         for (ddp = &_nsc_dev_pend; *ddp; ddp = &(*ddp)->nsc_next)
2143                 if (*ddp == dev) {
2144                         *ddp = dev->nsc_next;
2145                         break;
2146                 }
2147 
2148         mutex_exit(&_nsc_io_lock);
2149 
2150         mutex_destroy(&dev->nsc_lock);
2151         cv_destroy(&dev->nsc_cv);
2152         nsc_strfree(dev->nsc_path);
2153 
2154         nsc_kmem_free(dev, sizeof (*dev));
2155 }
2156 
2157 
2158 /*
2159  * static nsc_io_t *
2160  * _nsc_alloc_io (int id, char *name, int flag)
2161  *      Allocate an I/O structure.
2162  *
2163  * Calling/Exit State:
2164  *      Returns the address of the I/O structure, or NULL.
2165  */
2166 static nsc_io_t *
2167 _nsc_alloc_io(id, name, flag)
2168 int id;
2169 char *name;
2170 int flag;
2171 {
2172         nsc_io_t *io;
2173 
2174         if (!(io = (nsc_io_t *)nsc_kmem_zalloc(
2175                         sizeof (*io), KM_NOSLEEP, _nsc_local_mem)))
2176                 return (NULL);
2177 
2178         cv_init(&io->cv, NULL, CV_DRIVER, NULL);
2179 
2180         io->id = id;
2181         io->name = name;
2182         io->flag = flag;
2183 
2184         return (io);
2185 }
2186 
2187 
2188 /*
2189  * static void
2190  * _nsc_free_io (int id, char *name, int flag)
2191  *      Free an I/O structure.
2192  *
2193  * Calling/Exit State:
2194  *      Free the I/O structure and remove it from the chain.
2195  */
2196 static void
2197 _nsc_free_io(io)
2198 nsc_io_t *io;
2199 {
2200         nsc_io_t **iop;
2201 
2202         mutex_enter(&_nsc_io_lock);
2203 
2204         for (iop = &_nsc_io_top; *iop; iop = &(*iop)->next)
2205                 if (*iop == io)
2206                         break;
2207 
2208         if (*iop)
2209                 (*iop) = io->next;
2210 
2211         mutex_exit(&_nsc_io_lock);
2212 
2213         cv_destroy(&io->cv);
2214         nsc_kmem_free(io, sizeof (*io));
2215 }