The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/common/fs/zfs/space_map.c

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    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/zfs_context.h>
   27 #include <sys/spa.h>
   28 #include <sys/dmu.h>
   29 #include <sys/zio.h>
   30 #include <sys/space_map.h>
   31 
   32 /*
   33  * Space map routines.
   34  * NOTE: caller is responsible for all locking.
   35  */
   36 static int
   37 space_map_seg_compare(const void *x1, const void *x2)
   38 {
   39         const space_seg_t *s1 = x1;
   40         const space_seg_t *s2 = x2;
   41 
   42         if (s1->ss_start < s2->ss_start) {
   43                 if (s1->ss_end > s2->ss_start)
   44                         return (0);
   45                 return (-1);
   46         }
   47         if (s1->ss_start > s2->ss_start) {
   48                 if (s1->ss_start < s2->ss_end)
   49                         return (0);
   50                 return (1);
   51         }
   52         return (0);
   53 }
   54 
   55 void
   56 space_map_create(space_map_t *sm, uint64_t start, uint64_t size, uint8_t shift,
   57         kmutex_t *lp)
   58 {
   59         bzero(sm, sizeof (*sm));
   60 
   61         cv_init(&sm->sm_load_cv, NULL, CV_DEFAULT, NULL);
   62 
   63         avl_create(&sm->sm_root, space_map_seg_compare,
   64             sizeof (space_seg_t), offsetof(struct space_seg, ss_node));
   65 
   66         sm->sm_start = start;
   67         sm->sm_size = size;
   68         sm->sm_shift = shift;
   69         sm->sm_lock = lp;
   70 }
   71 
   72 void
   73 space_map_destroy(space_map_t *sm)
   74 {
   75         ASSERT(!sm->sm_loaded && !sm->sm_loading);
   76         VERIFY3U(sm->sm_space, ==, 0);
   77         avl_destroy(&sm->sm_root);
   78         cv_destroy(&sm->sm_load_cv);
   79 }
   80 
   81 void
   82 space_map_add(space_map_t *sm, uint64_t start, uint64_t size)
   83 {
   84         avl_index_t where;
   85         space_seg_t ssearch, *ss_before, *ss_after, *ss;
   86         uint64_t end = start + size;
   87         int merge_before, merge_after;
   88 
   89         ASSERT(MUTEX_HELD(sm->sm_lock));
   90         VERIFY(size != 0);
   91         VERIFY3U(start, >=, sm->sm_start);
   92         VERIFY3U(end, <=, sm->sm_start + sm->sm_size);
   93         VERIFY(sm->sm_space + size <= sm->sm_size);
   94         VERIFY(P2PHASE(start, 1ULL << sm->sm_shift) == 0);
   95         VERIFY(P2PHASE(size, 1ULL << sm->sm_shift) == 0);
   96 
   97         ssearch.ss_start = start;
   98         ssearch.ss_end = end;
   99         ss = avl_find(&sm->sm_root, &ssearch, &where);
  100 
  101         if (ss != NULL && ss->ss_start <= start && ss->ss_end >= end) {
  102                 zfs_panic_recover("zfs: allocating allocated segment"
  103                     "(offset=%llu size=%llu)\n",
  104                     (longlong_t)start, (longlong_t)size);
  105                 return;
  106         }
  107 
  108         /* Make sure we don't overlap with either of our neighbors */
  109         VERIFY(ss == NULL);
  110 
  111         ss_before = avl_nearest(&sm->sm_root, where, AVL_BEFORE);
  112         ss_after = avl_nearest(&sm->sm_root, where, AVL_AFTER);
  113 
  114         merge_before = (ss_before != NULL && ss_before->ss_end == start);
  115         merge_after = (ss_after != NULL && ss_after->ss_start == end);
  116 
  117         if (merge_before && merge_after) {
  118                 avl_remove(&sm->sm_root, ss_before);
  119                 if (sm->sm_pp_root) {
  120                         avl_remove(sm->sm_pp_root, ss_before);
  121                         avl_remove(sm->sm_pp_root, ss_after);
  122                 }
  123                 ss_after->ss_start = ss_before->ss_start;
  124                 kmem_free(ss_before, sizeof (*ss_before));
  125                 ss = ss_after;
  126         } else if (merge_before) {
  127                 ss_before->ss_end = end;
  128                 if (sm->sm_pp_root)
  129                         avl_remove(sm->sm_pp_root, ss_before);
  130                 ss = ss_before;
  131         } else if (merge_after) {
  132                 ss_after->ss_start = start;
  133                 if (sm->sm_pp_root)
  134                         avl_remove(sm->sm_pp_root, ss_after);
  135                 ss = ss_after;
  136         } else {
  137                 ss = kmem_alloc(sizeof (*ss), KM_SLEEP);
  138                 ss->ss_start = start;
  139                 ss->ss_end = end;
  140                 avl_insert(&sm->sm_root, ss, where);
  141         }
  142 
  143         if (sm->sm_pp_root)
  144                 avl_add(sm->sm_pp_root, ss);
  145 
  146         sm->sm_space += size;
  147 }
  148 
  149 void
  150 space_map_remove(space_map_t *sm, uint64_t start, uint64_t size)
  151 {
  152         avl_index_t where;
  153         space_seg_t ssearch, *ss, *newseg;
  154         uint64_t end = start + size;
  155         int left_over, right_over;
  156 
  157         ASSERT(MUTEX_HELD(sm->sm_lock));
  158         VERIFY(size != 0);
  159         VERIFY(P2PHASE(start, 1ULL << sm->sm_shift) == 0);
  160         VERIFY(P2PHASE(size, 1ULL << sm->sm_shift) == 0);
  161 
  162         ssearch.ss_start = start;
  163         ssearch.ss_end = end;
  164         ss = avl_find(&sm->sm_root, &ssearch, &where);
  165 
  166         /* Make sure we completely overlap with someone */
  167         if (ss == NULL) {
  168                 zfs_panic_recover("zfs: freeing free segment "
  169                     "(offset=%llu size=%llu)",
  170                     (longlong_t)start, (longlong_t)size);
  171                 return;
  172         }
  173         VERIFY3U(ss->ss_start, <=, start);
  174         VERIFY3U(ss->ss_end, >=, end);
  175         VERIFY(sm->sm_space - size <= sm->sm_size);
  176 
  177         left_over = (ss->ss_start != start);
  178         right_over = (ss->ss_end != end);
  179 
  180         if (sm->sm_pp_root)
  181                 avl_remove(sm->sm_pp_root, ss);
  182 
  183         if (left_over && right_over) {
  184                 newseg = kmem_alloc(sizeof (*newseg), KM_SLEEP);
  185                 newseg->ss_start = end;
  186                 newseg->ss_end = ss->ss_end;
  187                 ss->ss_end = start;
  188                 avl_insert_here(&sm->sm_root, newseg, ss, AVL_AFTER);
  189                 if (sm->sm_pp_root)
  190                         avl_add(sm->sm_pp_root, newseg);
  191         } else if (left_over) {
  192                 ss->ss_end = start;
  193         } else if (right_over) {
  194                 ss->ss_start = end;
  195         } else {
  196                 avl_remove(&sm->sm_root, ss);
  197                 kmem_free(ss, sizeof (*ss));
  198                 ss = NULL;
  199         }
  200 
  201         if (sm->sm_pp_root && ss != NULL)
  202                 avl_add(sm->sm_pp_root, ss);
  203 
  204         sm->sm_space -= size;
  205 }
  206 
  207 boolean_t
  208 space_map_contains(space_map_t *sm, uint64_t start, uint64_t size)
  209 {
  210         avl_index_t where;
  211         space_seg_t ssearch, *ss;
  212         uint64_t end = start + size;
  213 
  214         ASSERT(MUTEX_HELD(sm->sm_lock));
  215         VERIFY(size != 0);
  216         VERIFY(P2PHASE(start, 1ULL << sm->sm_shift) == 0);
  217         VERIFY(P2PHASE(size, 1ULL << sm->sm_shift) == 0);
  218 
  219         ssearch.ss_start = start;
  220         ssearch.ss_end = end;
  221         ss = avl_find(&sm->sm_root, &ssearch, &where);
  222 
  223         return (ss != NULL && ss->ss_start <= start && ss->ss_end >= end);
  224 }
  225 
  226 void
  227 space_map_vacate(space_map_t *sm, space_map_func_t *func, space_map_t *mdest)
  228 {
  229         space_seg_t *ss;
  230         void *cookie = NULL;
  231 
  232         ASSERT(MUTEX_HELD(sm->sm_lock));
  233 
  234         while ((ss = avl_destroy_nodes(&sm->sm_root, &cookie)) != NULL) {
  235                 if (func != NULL)
  236                         func(mdest, ss->ss_start, ss->ss_end - ss->ss_start);
  237                 kmem_free(ss, sizeof (*ss));
  238         }
  239         sm->sm_space = 0;
  240 }
  241 
  242 void
  243 space_map_walk(space_map_t *sm, space_map_func_t *func, space_map_t *mdest)
  244 {
  245         space_seg_t *ss;
  246 
  247         ASSERT(MUTEX_HELD(sm->sm_lock));
  248 
  249         for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
  250                 func(mdest, ss->ss_start, ss->ss_end - ss->ss_start);
  251 }
  252 
  253 /*
  254  * Wait for any in-progress space_map_load() to complete.
  255  */
  256 void
  257 space_map_load_wait(space_map_t *sm)
  258 {
  259         ASSERT(MUTEX_HELD(sm->sm_lock));
  260 
  261         while (sm->sm_loading) {
  262                 ASSERT(!sm->sm_loaded);
  263                 cv_wait(&sm->sm_load_cv, sm->sm_lock);
  264         }
  265 }
  266 
  267 /*
  268  * Note: space_map_load() will drop sm_lock across dmu_read() calls.
  269  * The caller must be OK with this.
  270  */
  271 int
  272 space_map_load(space_map_t *sm, space_map_ops_t *ops, uint8_t maptype,
  273         space_map_obj_t *smo, objset_t *os)
  274 {
  275         uint64_t *entry, *entry_map, *entry_map_end;
  276         uint64_t bufsize, size, offset, end, space;
  277         uint64_t mapstart = sm->sm_start;
  278         int error = 0;
  279 
  280         ASSERT(MUTEX_HELD(sm->sm_lock));
  281         ASSERT(!sm->sm_loaded);
  282         ASSERT(!sm->sm_loading);
  283 
  284         sm->sm_loading = B_TRUE;
  285         end = smo->smo_objsize;
  286         space = smo->smo_alloc;
  287 
  288         ASSERT(sm->sm_ops == NULL);
  289         VERIFY3U(sm->sm_space, ==, 0);
  290 
  291         if (maptype == SM_FREE) {
  292                 space_map_add(sm, sm->sm_start, sm->sm_size);
  293                 space = sm->sm_size - space;
  294         }
  295 
  296         bufsize = 1ULL << SPACE_MAP_BLOCKSHIFT;
  297         entry_map = zio_buf_alloc(bufsize);
  298 
  299         mutex_exit(sm->sm_lock);
  300         if (end > bufsize)
  301                 dmu_prefetch(os, smo->smo_object, bufsize, end - bufsize);
  302         mutex_enter(sm->sm_lock);
  303 
  304         for (offset = 0; offset < end; offset += bufsize) {
  305                 size = MIN(end - offset, bufsize);
  306                 VERIFY(P2PHASE(size, sizeof (uint64_t)) == 0);
  307                 VERIFY(size != 0);
  308 
  309                 dprintf("object=%llu  offset=%llx  size=%llx\n",
  310                     smo->smo_object, offset, size);
  311 
  312                 mutex_exit(sm->sm_lock);
  313                 error = dmu_read(os, smo->smo_object, offset, size, entry_map,
  314                     DMU_READ_PREFETCH);
  315                 mutex_enter(sm->sm_lock);
  316                 if (error != 0)
  317                         break;
  318 
  319                 entry_map_end = entry_map + (size / sizeof (uint64_t));
  320                 for (entry = entry_map; entry < entry_map_end; entry++) {
  321                         uint64_t e = *entry;
  322 
  323                         if (SM_DEBUG_DECODE(e))         /* Skip debug entries */
  324                                 continue;
  325 
  326                         (SM_TYPE_DECODE(e) == maptype ?
  327                             space_map_add : space_map_remove)(sm,
  328                             (SM_OFFSET_DECODE(e) << sm->sm_shift) + mapstart,
  329                             SM_RUN_DECODE(e) << sm->sm_shift);
  330                 }
  331         }
  332 
  333         if (error == 0) {
  334                 VERIFY3U(sm->sm_space, ==, space);
  335 
  336                 sm->sm_loaded = B_TRUE;
  337                 sm->sm_ops = ops;
  338                 if (ops != NULL)
  339                         ops->smop_load(sm);
  340         } else {
  341                 space_map_vacate(sm, NULL, NULL);
  342         }
  343 
  344         zio_buf_free(entry_map, bufsize);
  345 
  346         sm->sm_loading = B_FALSE;
  347 
  348         cv_broadcast(&sm->sm_load_cv);
  349 
  350         return (error);
  351 }
  352 
  353 void
  354 space_map_unload(space_map_t *sm)
  355 {
  356         ASSERT(MUTEX_HELD(sm->sm_lock));
  357 
  358         if (sm->sm_loaded && sm->sm_ops != NULL)
  359                 sm->sm_ops->smop_unload(sm);
  360 
  361         sm->sm_loaded = B_FALSE;
  362         sm->sm_ops = NULL;
  363 
  364         space_map_vacate(sm, NULL, NULL);
  365 }
  366 
  367 uint64_t
  368 space_map_maxsize(space_map_t *sm)
  369 {
  370         ASSERT(sm->sm_ops != NULL);
  371         return (sm->sm_ops->smop_max(sm));
  372 }
  373 
  374 uint64_t
  375 space_map_alloc(space_map_t *sm, uint64_t size)
  376 {
  377         uint64_t start;
  378 
  379         start = sm->sm_ops->smop_alloc(sm, size);
  380         if (start != -1ULL)
  381                 space_map_remove(sm, start, size);
  382         return (start);
  383 }
  384 
  385 void
  386 space_map_claim(space_map_t *sm, uint64_t start, uint64_t size)
  387 {
  388         sm->sm_ops->smop_claim(sm, start, size);
  389         space_map_remove(sm, start, size);
  390 }
  391 
  392 void
  393 space_map_free(space_map_t *sm, uint64_t start, uint64_t size)
  394 {
  395         space_map_add(sm, start, size);
  396         sm->sm_ops->smop_free(sm, start, size);
  397 }
  398 
  399 /*
  400  * Note: space_map_sync() will drop sm_lock across dmu_write() calls.
  401  */
  402 void
  403 space_map_sync(space_map_t *sm, uint8_t maptype,
  404         space_map_obj_t *smo, objset_t *os, dmu_tx_t *tx)
  405 {
  406         spa_t *spa = dmu_objset_spa(os);
  407         void *cookie = NULL;
  408         space_seg_t *ss;
  409         uint64_t bufsize, start, size, run_len;
  410         uint64_t *entry, *entry_map, *entry_map_end;
  411 
  412         ASSERT(MUTEX_HELD(sm->sm_lock));
  413 
  414         if (sm->sm_space == 0)
  415                 return;
  416 
  417         dprintf("object %4llu, txg %llu, pass %d, %c, count %lu, space %llx\n",
  418             smo->smo_object, dmu_tx_get_txg(tx), spa_sync_pass(spa),
  419             maptype == SM_ALLOC ? 'A' : 'F', avl_numnodes(&sm->sm_root),
  420             sm->sm_space);
  421 
  422         if (maptype == SM_ALLOC)
  423                 smo->smo_alloc += sm->sm_space;
  424         else
  425                 smo->smo_alloc -= sm->sm_space;
  426 
  427         bufsize = (8 + avl_numnodes(&sm->sm_root)) * sizeof (uint64_t);
  428         bufsize = MIN(bufsize, 1ULL << SPACE_MAP_BLOCKSHIFT);
  429         entry_map = zio_buf_alloc(bufsize);
  430         entry_map_end = entry_map + (bufsize / sizeof (uint64_t));
  431         entry = entry_map;
  432 
  433         *entry++ = SM_DEBUG_ENCODE(1) |
  434             SM_DEBUG_ACTION_ENCODE(maptype) |
  435             SM_DEBUG_SYNCPASS_ENCODE(spa_sync_pass(spa)) |
  436             SM_DEBUG_TXG_ENCODE(dmu_tx_get_txg(tx));
  437 
  438         while ((ss = avl_destroy_nodes(&sm->sm_root, &cookie)) != NULL) {
  439                 size = ss->ss_end - ss->ss_start;
  440                 start = (ss->ss_start - sm->sm_start) >> sm->sm_shift;
  441 
  442                 sm->sm_space -= size;
  443                 size >>= sm->sm_shift;
  444 
  445                 while (size) {
  446                         run_len = MIN(size, SM_RUN_MAX);
  447 
  448                         if (entry == entry_map_end) {
  449                                 mutex_exit(sm->sm_lock);
  450                                 dmu_write(os, smo->smo_object, smo->smo_objsize,
  451                                     bufsize, entry_map, tx);
  452                                 mutex_enter(sm->sm_lock);
  453                                 smo->smo_objsize += bufsize;
  454                                 entry = entry_map;
  455                         }
  456 
  457                         *entry++ = SM_OFFSET_ENCODE(start) |
  458                             SM_TYPE_ENCODE(maptype) |
  459                             SM_RUN_ENCODE(run_len);
  460 
  461                         start += run_len;
  462                         size -= run_len;
  463                 }
  464                 kmem_free(ss, sizeof (*ss));
  465         }
  466 
  467         if (entry != entry_map) {
  468                 size = (entry - entry_map) * sizeof (uint64_t);
  469                 mutex_exit(sm->sm_lock);
  470                 dmu_write(os, smo->smo_object, smo->smo_objsize,
  471                     size, entry_map, tx);
  472                 mutex_enter(sm->sm_lock);
  473                 smo->smo_objsize += size;
  474         }
  475 
  476         zio_buf_free(entry_map, bufsize);
  477 
  478         VERIFY3U(sm->sm_space, ==, 0);
  479 }
  480 
  481 void
  482 space_map_truncate(space_map_obj_t *smo, objset_t *os, dmu_tx_t *tx)
  483 {
  484         VERIFY(dmu_free_range(os, smo->smo_object, 0, -1ULL, tx) == 0);
  485 
  486         smo->smo_objsize = 0;
  487         smo->smo_alloc = 0;
  488 }
  489 
  490 /*
  491  * Space map reference trees.
  492  *
  493  * A space map is a collection of integers.  Every integer is either
  494  * in the map, or it's not.  A space map reference tree generalizes
  495  * the idea: it allows its members to have arbitrary reference counts,
  496  * as opposed to the implicit reference count of 0 or 1 in a space map.
  497  * This representation comes in handy when computing the union or
  498  * intersection of multiple space maps.  For example, the union of
  499  * N space maps is the subset of the reference tree with refcnt >= 1.
  500  * The intersection of N space maps is the subset with refcnt >= N.
  501  *
  502  * [It's very much like a Fourier transform.  Unions and intersections
  503  * are hard to perform in the 'space map domain', so we convert the maps
  504  * into the 'reference count domain', where it's trivial, then invert.]
  505  *
  506  * vdev_dtl_reassess() uses computations of this form to determine
  507  * DTL_MISSING and DTL_OUTAGE for interior vdevs -- e.g. a RAID-Z vdev
  508  * has an outage wherever refcnt >= vdev_nparity + 1, and a mirror vdev
  509  * has an outage wherever refcnt >= vdev_children.
  510  */
  511 static int
  512 space_map_ref_compare(const void *x1, const void *x2)
  513 {
  514         const space_ref_t *sr1 = x1;
  515         const space_ref_t *sr2 = x2;
  516 
  517         if (sr1->sr_offset < sr2->sr_offset)
  518                 return (-1);
  519         if (sr1->sr_offset > sr2->sr_offset)
  520                 return (1);
  521 
  522         if (sr1 < sr2)
  523                 return (-1);
  524         if (sr1 > sr2)
  525                 return (1);
  526 
  527         return (0);
  528 }
  529 
  530 void
  531 space_map_ref_create(avl_tree_t *t)
  532 {
  533         avl_create(t, space_map_ref_compare,
  534             sizeof (space_ref_t), offsetof(space_ref_t, sr_node));
  535 }
  536 
  537 void
  538 space_map_ref_destroy(avl_tree_t *t)
  539 {
  540         space_ref_t *sr;
  541         void *cookie = NULL;
  542 
  543         while ((sr = avl_destroy_nodes(t, &cookie)) != NULL)
  544                 kmem_free(sr, sizeof (*sr));
  545 
  546         avl_destroy(t);
  547 }
  548 
  549 static void
  550 space_map_ref_add_node(avl_tree_t *t, uint64_t offset, int64_t refcnt)
  551 {
  552         space_ref_t *sr;
  553 
  554         sr = kmem_alloc(sizeof (*sr), KM_SLEEP);
  555         sr->sr_offset = offset;
  556         sr->sr_refcnt = refcnt;
  557 
  558         avl_add(t, sr);
  559 }
  560 
  561 void
  562 space_map_ref_add_seg(avl_tree_t *t, uint64_t start, uint64_t end,
  563         int64_t refcnt)
  564 {
  565         space_map_ref_add_node(t, start, refcnt);
  566         space_map_ref_add_node(t, end, -refcnt);
  567 }
  568 
  569 /*
  570  * Convert (or add) a space map into a reference tree.
  571  */
  572 void
  573 space_map_ref_add_map(avl_tree_t *t, space_map_t *sm, int64_t refcnt)
  574 {
  575         space_seg_t *ss;
  576 
  577         ASSERT(MUTEX_HELD(sm->sm_lock));
  578 
  579         for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
  580                 space_map_ref_add_seg(t, ss->ss_start, ss->ss_end, refcnt);
  581 }
  582 
  583 /*
  584  * Convert a reference tree into a space map.  The space map will contain
  585  * all members of the reference tree for which refcnt >= minref.
  586  */
  587 void
  588 space_map_ref_generate_map(avl_tree_t *t, space_map_t *sm, int64_t minref)
  589 {
  590         uint64_t start = -1ULL;
  591         int64_t refcnt = 0;
  592         space_ref_t *sr;
  593 
  594         ASSERT(MUTEX_HELD(sm->sm_lock));
  595 
  596         space_map_vacate(sm, NULL, NULL);
  597 
  598         for (sr = avl_first(t); sr != NULL; sr = AVL_NEXT(t, sr)) {
  599                 refcnt += sr->sr_refcnt;
  600                 if (refcnt >= minref) {
  601                         if (start == -1ULL) {
  602                                 start = sr->sr_offset;
  603                         }
  604                 } else {
  605                         if (start != -1ULL) {
  606                                 uint64_t end = sr->sr_offset;
  607                                 ASSERT(start <= end);
  608                                 if (end > start)
  609                                         space_map_add(sm, start, end - start);
  610                                 start = -1ULL;
  611                         }
  612                 }
  613         }
  614         ASSERT(refcnt == 0);
  615         ASSERT(start == -1ULL);
  616 }

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