fs/btrfs/space-info.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include "misc.h"
   4 #include "ctree.h"
   5 #include "space-info.h"
   6 #include "sysfs.h"
   7 #include "volumes.h"
   8 #include "free-space-cache.h"
   9 #include "ordered-data.h"
  10 #include "transaction.h"
  11 #include "block-group.h"
  12
  13 /*
  14  * HOW DOES SPACE RESERVATION WORK
  15  *
  16  * If you want to know about delalloc specifically, there is a separate comment
  17  * for that with the delalloc code.  This comment is about how the whole system
  18  * works generally.
  19  *
  20  * BASIC CONCEPTS
  21  *
  22  *   1) space_info.  This is the ultimate arbiter of how much space we can use.
  23  *   There's a description of the bytes_ fields with the struct declaration,
  24  *   refer to that for specifics on each field.  Suffice it to say that for
  25  *   reservations we care about total_bytes - SUM(space_info->bytes_) when
  26  *   determining if there is space to make an allocation.  There is a space_info
  27  *   for METADATA, SYSTEM, and DATA areas.
  28  *
  29  *   2) block_rsv's.  These are basically buckets for every different type of
  30  *   metadata reservation we have.  You can see the comment in the block_rsv
  31  *   code on the rules for each type, but generally block_rsv->reserved is how
  32  *   much space is accounted for in space_info->bytes_may_use.
  33  *
  34  *   3) btrfs_calc*_size.  These are the worst case calculations we used based
  35  *   on the number of items we will want to modify.  We have one for changing
  36  *   items, and one for inserting new items.  Generally we use these helpers to
  37  *   determine the size of the block reserves, and then use the actual bytes
  38  *   values to adjust the space_info counters.
  39  *
  40  * MAKING RESERVATIONS, THE NORMAL CASE
  41  *
  42  *   We call into either btrfs_reserve_data_bytes() or
  43  *   btrfs_reserve_metadata_bytes(), depending on which we're looking for, with
  44  *   num_bytes we want to reserve.
  45  *
  46  *   ->reserve
  47  *     space_info->bytes_may_reserve += num_bytes
  48  *
  49  *   ->extent allocation
  50  *     Call btrfs_add_reserved_bytes() which does
  51  *     space_info->bytes_may_reserve -= num_bytes
  52  *     space_info->bytes_reserved += extent_bytes
  53  *
  54  *   ->insert reference
  55  *     Call btrfs_update_block_group() which does
  56  *     space_info->bytes_reserved -= extent_bytes
  57  *     space_info->bytes_used += extent_bytes
  58  *
  59  * MAKING RESERVATIONS, FLUSHING NORMALLY (non-priority)
  60  *
  61  *   Assume we are unable to simply make the reservation because we do not have
  62  *   enough space
  63  *
  64  *   -> __reserve_bytes
  65  *     create a reserve_ticket with ->bytes set to our reservation, add it to
  66  *     the tail of space_info->tickets, kick async flush thread
  67  *
  68  *   ->handle_reserve_ticket
  69  *     wait on ticket->wait for ->bytes to be reduced to 0, or ->error to be set
  70  *     on the ticket.
  71  *
  72  *   -> btrfs_async_reclaim_metadata_space/btrfs_async_reclaim_data_space
  73  *     Flushes various things attempting to free up space.
  74  *
  75  *   -> btrfs_try_granting_tickets()
  76  *     This is called by anything that either subtracts space from
  77  *     space_info->bytes_may_use, ->bytes_pinned, etc, or adds to the
  78  *     space_info->total_bytes.  This loops through the ->priority_tickets and
  79  *     then the ->tickets list checking to see if the reservation can be
  80  *     completed.  If it can the space is added to space_info->bytes_may_use and
  81  *     the ticket is woken up.
  82  *
  83  *   -> ticket wakeup
  84  *     Check if ->bytes == 0, if it does we got our reservation and we can carry
  85  *     on, if not return the appropriate error (ENOSPC, but can be EINTR if we
  86  *     were interrupted.)
  87  *
  88  * MAKING RESERVATIONS, FLUSHING HIGH PRIORITY
  89  *
  90  *   Same as the above, except we add ourselves to the
  91  *   space_info->priority_tickets, and we do not use ticket->wait, we simply
  92  *   call flush_space() ourselves for the states that are safe for us to call
  93  *   without deadlocking and hope for the best.
  94  *
  95  * THE FLUSHING STATES
  96  *
  97  *   Generally speaking we will have two cases for each state, a "nice" state
  98  *   and a "ALL THE THINGS" state.  In btrfs we delay a lot of work in order to
  99  *   reduce the locking over head on the various trees, and even to keep from
 100  *   doing any work at all in the case of delayed refs.  Each of these delayed
 101  *   things however hold reservations, and so letting them run allows us to
 102  *   reclaim space so we can make new reservations.
 103  *
 104  *   FLUSH_DELAYED_ITEMS
 105  *     Every inode has a delayed item to update the inode.  Take a simple write
 106  *     for example, we would update the inode item at write time to update the
 107  *     mtime, and then again at finish_ordered_io() time in order to update the
 108  *     isize or bytes.  We keep these delayed items to coalesce these operations
 109  *     into a single operation done on demand.  These are an easy way to reclaim
 110  *     metadata space.
 111  *
 112  *   FLUSH_DELALLOC
 113  *     Look at the delalloc comment to get an idea of how much space is reserved
 114  *     for delayed allocation.  We can reclaim some of this space simply by
 115  *     running delalloc, but usually we need to wait for ordered extents to
 116  *     reclaim the bulk of this space.
 117  *
 118  *   FLUSH_DELAYED_REFS
 119  *     We have a block reserve for the outstanding delayed refs space, and every
 120  *     delayed ref operation holds a reservation.  Running these is a quick way
 121  *     to reclaim space, but we want to hold this until the end because COW can
 122  *     churn a lot and we can avoid making some extent tree modifications if we
 123  *     are able to delay for as long as possible.
 124  *
 125  *   ALLOC_CHUNK
 126  *     We will skip this the first time through space reservation, because of
 127  *     overcommit and we don't want to have a lot of useless metadata space when
 128  *     our worst case reservations will likely never come true.
 129  *
 130  *   RUN_DELAYED_IPUTS
 131  *     If we're freeing inodes we're likely freeing checksums, file extent
 132  *     items, and extent tree items.  Loads of space could be freed up by these
 133  *     operations, however they won't be usable until the transaction commits.
 134  *
 135  *   COMMIT_TRANS
 136  *     This will commit the transaction.  Historically we had a lot of logic
 137  *     surrounding whether or not we'd commit the transaction, but this waits born
 138  *     out of a pre-tickets era where we could end up committing the transaction
 139  *     thousands of times in a row without making progress.  Now thanks to our
 140  *     ticketing system we know if we're not making progress and can error
 141  *     everybody out after a few commits rather than burning the disk hoping for
 142  *     a different answer.
 143  *
 144  * OVERCOMMIT
 145  *
 146  *   Because we hold so many reservations for metadata we will allow you to
 147  *   reserve more space than is currently free in the currently allocate
 148  *   metadata space.  This only happens with metadata, data does not allow
 149  *   overcommitting.
 150  *
 151  *   You can see the current logic for when we allow overcommit in
 152  *   btrfs_can_overcommit(), but it only applies to unallocated space.  If there
 153  *   is no unallocated space to be had, all reservations are kept within the
 154  *   free space in the allocated metadata chunks.
 155  *
 156  *   Because of overcommitting, you generally want to use the
 157  *   btrfs_can_overcommit() logic for metadata allocations, as it does the right
 158  *   thing with or without extra unallocated space.
 159  */
 160
 161 u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
 162                           bool may_use_included)
 163 {
 164         ASSERT(s_info);
 165         return s_info->bytes_used + s_info->bytes_reserved +
 166                 s_info->bytes_pinned + s_info->bytes_readonly +
 167                 s_info->bytes_zone_unusable +
 168                 (may_use_included ? s_info->bytes_may_use : 0);
 169 }
 170
 171 /*
 172  * after adding space to the filesystem, we need to clear the full flags
 173  * on all the space infos.
 174  */
 175 void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
 176 {
 177         struct list_head *head = &info->space_info;
 178         struct btrfs_space_info *found;
 179
 180         list_for_each_entry(found, head, list)
 181                 found->full = 0;
 182 }
 183
 184 static int create_space_info(struct btrfs_fs_info *info, u64 flags)
 185 {
 186
 187         struct btrfs_space_info *space_info;
 188         int i;
 189         int ret;
 190
 191         space_info = kzalloc(sizeof(*space_info), GFP_NOFS);
 192         if (!space_info)
 193                 return -ENOMEM;
 194
 195         for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
 196                 INIT_LIST_HEAD(&space_info->block_groups[i]);
 197         init_rwsem(&space_info->groups_sem);
 198         spin_lock_init(&space_info->lock);
 199         space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
 200         space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
 201         INIT_LIST_HEAD(&space_info->ro_bgs);
 202         INIT_LIST_HEAD(&space_info->tickets);
 203         INIT_LIST_HEAD(&space_info->priority_tickets);
 204         space_info->clamp = 1;
 205
 206         ret = btrfs_sysfs_add_space_info_type(info, space_info);
 207         if (ret)
 208                 return ret;
 209
 210         list_add(&space_info->list, &info->space_info);
 211         if (flags & BTRFS_BLOCK_GROUP_DATA)
 212                 info->data_sinfo = space_info;
 213
 214         return ret;
 215 }
 216
 217 int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 218 {
 219         struct btrfs_super_block *disk_super;
 220         u64 features;
 221         u64 flags;
 222         int mixed = 0;
 223         int ret;
 224
 225         disk_super = fs_info->super_copy;
 226         if (!btrfs_super_root(disk_super))
 227                 return -EINVAL;
 228
 229         features = btrfs_super_incompat_flags(disk_super);
 230         if (features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
 231                 mixed = 1;
 232
 233         flags = BTRFS_BLOCK_GROUP_SYSTEM;
 234         ret = create_space_info(fs_info, flags);
 235         if (ret)
 236                 goto out;
 237
 238         if (mixed) {
 239                 flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
 240                 ret = create_space_info(fs_info, flags);
 241         } else {
 242                 flags = BTRFS_BLOCK_GROUP_METADATA;
 243                 ret = create_space_info(fs_info, flags);
 244                 if (ret)
 245                         goto out;
 246
 247                 flags = BTRFS_BLOCK_GROUP_DATA;
 248                 ret = create_space_info(fs_info, flags);
 249         }
 250 out:
 251         return ret;
 252 }
 253
 254 void btrfs_update_space_info(struct btrfs_fs_info *info, u64 flags,
 255                              u64 total_bytes, u64 bytes_used,
 256                              u64 bytes_readonly, u64 bytes_zone_unusable,
 257                              struct btrfs_space_info **space_info)
 258 {
 259         struct btrfs_space_info *found;
 260         int factor;
 261
 262         factor = btrfs_bg_type_to_factor(flags);
 263
 264         found = btrfs_find_space_info(info, flags);
 265         ASSERT(found);
 266         spin_lock(&found->lock);
 267         found->total_bytes += total_bytes;
 268         found->disk_total += total_bytes * factor;
 269         found->bytes_used += bytes_used;
 270         found->disk_used += bytes_used * factor;
 271         found->bytes_readonly += bytes_readonly;
 272         found->bytes_zone_unusable += bytes_zone_unusable;
 273         if (total_bytes > 0)
 274                 found->full = 0;
 275         btrfs_try_granting_tickets(info, found);
 276         spin_unlock(&found->lock);
 277         *space_info = found;
 278 }
 279
 280 struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
 281                                                u64 flags)
 282 {
 283         struct list_head *head = &info->space_info;
 284         struct btrfs_space_info *found;
 285
 286         flags &= BTRFS_BLOCK_GROUP_TYPE_MASK;
 287
 288         list_for_each_entry(found, head, list) {
 289                 if (found->flags & flags)
 290                         return found;
 291         }
 292         return NULL;
 293 }
 294
 295 static u64 calc_available_free_space(struct btrfs_fs_info *fs_info,
 296                           struct btrfs_space_info *space_info,
 297                           enum btrfs_reserve_flush_enum flush)
 298 {
 299         u64 profile;
 300         u64 avail;
 301         int factor;
 302
 303         if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
 304                 profile = btrfs_system_alloc_profile(fs_info);
 305         else
 306                 profile = btrfs_metadata_alloc_profile(fs_info);
 307
 308         avail = atomic64_read(&fs_info->free_chunk_space);
 309
 310         /*
 311          * If we have dup, raid1 or raid10 then only half of the free
 312          * space is actually usable.  For raid56, the space info used
 313          * doesn't include the parity drive, so we don't have to
 314          * change the math
 315          */
 316         factor = btrfs_bg_type_to_factor(profile);
 317         avail = div_u64(avail, factor);
 318
 319         /*
 320          * If we aren't flushing all things, let us overcommit up to
 321          * 1/2th of the space. If we can flush, don't let us overcommit
 322          * too much, let it overcommit up to 1/8 of the space.
 323          */
 324         if (flush == BTRFS_RESERVE_FLUSH_ALL)
 325                 avail >>= 3;
 326         else
 327                 avail >>= 1;
 328         return avail;
 329 }
 330
 331 int btrfs_can_overcommit(struct btrfs_fs_info *fs_info,
 332                          struct btrfs_space_info *space_info, u64 bytes,
 333                          enum btrfs_reserve_flush_enum flush)
 334 {
 335         u64 avail;
 336         u64 used;
 337
 338         /* Don't overcommit when in mixed mode */
 339         if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
 340                 return 0;
 341
 342         used = btrfs_space_info_used(space_info, true);
 343         avail = calc_available_free_space(fs_info, space_info, flush);
 344
 345         if (used + bytes < space_info->total_bytes + avail)
 346                 return 1;
 347         return 0;
 348 }
 349
 350 static void remove_ticket(struct btrfs_space_info *space_info,
 351                           struct reserve_ticket *ticket)
 352 {
 353         if (!list_empty(&ticket->list)) {
 354                 list_del_init(&ticket->list);
 355                 ASSERT(space_info->reclaim_size >= ticket->bytes);
 356                 space_info->reclaim_size -= ticket->bytes;
 357         }
 358 }
 359
 360 /*
 361  * This is for space we already have accounted in space_info->bytes_may_use, so
 362  * basically when we're returning space from block_rsv's.
 363  */
 364 void btrfs_try_granting_tickets(struct btrfs_fs_info *fs_info,
 365                                 struct btrfs_space_info *space_info)
 366 {
 367         struct list_head *head;
 368         enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;
 369
 370         lockdep_assert_held(&space_info->lock);
 371
 372         head = &space_info->priority_tickets;
 373 again:
 374         while (!list_empty(head)) {
 375                 struct reserve_ticket *ticket;
 376                 u64 used = btrfs_space_info_used(space_info, true);
 377
 378                 ticket = list_first_entry(head, struct reserve_ticket, list);
 379
 380                 /* Check and see if our ticket can be satisfied now. */
 381                 if ((used + ticket->bytes <= space_info->total_bytes) ||
 382                     btrfs_can_overcommit(fs_info, space_info, ticket->bytes,
 383                                          flush)) {
 384                         btrfs_space_info_update_bytes_may_use(fs_info,
 385                                                               space_info,
 386                                                               ticket->bytes);
 387                         remove_ticket(space_info, ticket);
 388                         ticket->bytes = 0;
 389                         space_info->tickets_id++;
 390                         wake_up(&ticket->wait);
 391                 } else {
 392                         break;
 393                 }
 394         }
 395
 396         if (head == &space_info->priority_tickets) {
 397                 head = &space_info->tickets;
 398                 flush = BTRFS_RESERVE_FLUSH_ALL;
 399                 goto again;
 400         }
 401 }
 402
 403 #define DUMP_BLOCK_RSV(fs_info, rsv_name)                               \
 404 do {                                                                    \
 405         struct btrfs_block_rsv *__rsv = &(fs_info)->rsv_name;           \
 406         spin_lock(&__rsv->lock);                                        \
 407         btrfs_info(fs_info, #rsv_name ": size %llu reserved %llu",      \
 408                    __rsv->size, __rsv->reserved);                       \
 409         spin_unlock(&__rsv->lock);                                      \
 410 } while (0)
 411
 412 static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 413                                     struct btrfs_space_info *info)
 414 {
 415         lockdep_assert_held(&info->lock);
 416
 417         /* The free space could be negative in case of overcommit */
 418         btrfs_info(fs_info, "space_info %llu has %lld free, is %sfull",
 419                    info->flags,
 420                    (s64)(info->total_bytes - btrfs_space_info_used(info, true)),
 421                    info->full ? "" : "not ");
 422         btrfs_info(fs_info,
 423                 "space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu zone_unusable=%llu",
 424                 info->total_bytes, info->bytes_used, info->bytes_pinned,
 425                 info->bytes_reserved, info->bytes_may_use,
 426                 info->bytes_readonly, info->bytes_zone_unusable);
 427
 428         DUMP_BLOCK_RSV(fs_info, global_block_rsv);
 429         DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
 430         DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
 431         DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
 432         DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
 433
 434 }
 435
 436 void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 437                            struct btrfs_space_info *info, u64 bytes,
 438                            int dump_block_groups)
 439 {
 440         struct btrfs_block_group *cache;
 441         int index = 0;
 442
 443         spin_lock(&info->lock);
 444         __btrfs_dump_space_info(fs_info, info);
 445         spin_unlock(&info->lock);
 446
 447         if (!dump_block_groups)
 448                 return;
 449
 450         down_read(&info->groups_sem);
 451 again:
 452         list_for_each_entry(cache, &info->block_groups[index], list) {
 453                 spin_lock(&cache->lock);
 454                 btrfs_info(fs_info,
 455                         "block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %llu zone_unusable %s",
 456                         cache->start, cache->length, cache->used, cache->pinned,
 457                         cache->reserved, cache->zone_unusable,
 458                         cache->ro ? "[readonly]" : "");
 459                 spin_unlock(&cache->lock);
 460                 btrfs_dump_free_space(cache, bytes);
 461         }
 462         if (++index < BTRFS_NR_RAID_TYPES)
 463                 goto again;
 464         up_read(&info->groups_sem);
 465 }
 466
 467 static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
 468                                         u64 to_reclaim)
 469 {
 470         u64 bytes;
 471         u64 nr;
 472
 473         bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
 474         nr = div64_u64(to_reclaim, bytes);
 475         if (!nr)
 476                 nr = 1;
 477         return nr;
 478 }
 479
 480 #define EXTENT_SIZE_PER_ITEM    SZ_256K
 481
 482 /*
 483  * shrink metadata reservation for delalloc
 484  */
 485 static void shrink_delalloc(struct btrfs_fs_info *fs_info,
 486                             struct btrfs_space_info *space_info,
 487                             u64 to_reclaim, bool wait_ordered,
 488                             bool for_preempt)
 489 {
 490         struct btrfs_trans_handle *trans;
 491         u64 delalloc_bytes;
 492         u64 ordered_bytes;
 493         u64 items;
 494         long time_left;
 495         int loops;
 496
 497         delalloc_bytes = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
 498         ordered_bytes = percpu_counter_sum_positive(&fs_info->ordered_bytes);
 499         if (delalloc_bytes == 0 && ordered_bytes == 0)
 500                 return;
 501
 502         /* Calc the number of the pages we need flush for space reservation */
 503         if (to_reclaim == U64_MAX) {
 504                 items = U64_MAX;
 505         } else {
 506                 /*
 507                  * to_reclaim is set to however much metadata we need to
 508                  * reclaim, but reclaiming that much data doesn't really track
 509                  * exactly.  What we really want to do is reclaim full inode's
 510                  * worth of reservations, however that's not available to us
 511                  * here.  We will take a fraction of the delalloc bytes for our
 512                  * flushing loops and hope for the best.  Delalloc will expand
 513                  * the amount we write to cover an entire dirty extent, which
 514                  * will reclaim the metadata reservation for that range.  If
 515                  * it's not enough subsequent flush stages will be more
 516                  * aggressive.
 517                  */
 518                 to_reclaim = max(to_reclaim, delalloc_bytes >> 3);
 519                 items = calc_reclaim_items_nr(fs_info, to_reclaim) * 2;
 520         }
 521
 522         trans = (struct btrfs_trans_handle *)current->journal_info;
 523
 524         /*
 525          * If we are doing more ordered than delalloc we need to just wait on
 526          * ordered extents, otherwise we'll waste time trying to flush delalloc
 527          * that likely won't give us the space back we need.
 528          */
 529         if (ordered_bytes > delalloc_bytes && !for_preempt)
 530                 wait_ordered = true;
 531
 532         loops = 0;
 533         while ((delalloc_bytes || ordered_bytes) && loops < 3) {
 534                 u64 temp = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
 535                 long nr_pages = min_t(u64, temp, LONG_MAX);
 536                 int async_pages;
 537
 538                 btrfs_start_delalloc_roots(fs_info, nr_pages, true);
 539
 540                 /*
 541                  * We need to make sure any outstanding async pages are now
 542                  * processed before we continue.  This is because things like
 543                  * sync_inode() try to be smart and skip writing if the inode is
 544                  * marked clean.  We don't use filemap_fwrite for flushing
 545                  * because we want to control how many pages we write out at a
 546                  * time, thus this is the only safe way to make sure we've
 547                  * waited for outstanding compressed workers to have started
 548                  * their jobs and thus have ordered extents set up properly.
 549                  *
 550                  * This exists because we do not want to wait for each
 551                  * individual inode to finish its async work, we simply want to
 552                  * start the IO on everybody, and then come back here and wait
 553                  * for all of the async work to catch up.  Once we're done with
 554                  * that we know we'll have ordered extents for everything and we
 555                  * can decide if we wait for that or not.
 556                  *
 557                  * If we choose to replace this in the future, make absolutely
 558                  * sure that the proper waiting is being done in the async case,
 559                  * as there have been bugs in that area before.
 560                  */
 561                 async_pages = atomic_read(&fs_info->async_delalloc_pages);
 562                 if (!async_pages)
 563                         goto skip_async;
 564
 565                 /*
 566                  * We don't want to wait forever, if we wrote less pages in this
 567                  * loop than we have outstanding, only wait for that number of
 568                  * pages, otherwise we can wait for all async pages to finish
 569                  * before continuing.
 570                  */
 571                 if (async_pages > nr_pages)
 572                         async_pages -= nr_pages;
 573                 else
 574                         async_pages = 0;
 575                 wait_event(fs_info->async_submit_wait,
 576                            atomic_read(&fs_info->async_delalloc_pages) <=
 577                            async_pages);
 578 skip_async:
 579                 loops++;
 580                 if (wait_ordered && !trans) {
 581                         btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
 582                 } else {
 583                         time_left = schedule_timeout_killable(1);
 584                         if (time_left)
 585                                 break;
 586                 }
 587
 588                 /*
 589                  * If we are for preemption we just want a one-shot of delalloc
 590                  * flushing so we can stop flushing if we decide we don't need
 591                  * to anymore.
 592                  */
 593                 if (for_preempt)
 594                         break;
 595
 596                 spin_lock(&space_info->lock);
 597                 if (list_empty(&space_info->tickets) &&
 598                     list_empty(&space_info->priority_tickets)) {
 599                         spin_unlock(&space_info->lock);
 600                         break;
 601                 }
 602                 spin_unlock(&space_info->lock);
 603
 604                 delalloc_bytes = percpu_counter_sum_positive(
 605                                                 &fs_info->delalloc_bytes);
 606                 ordered_bytes = percpu_counter_sum_positive(
 607                                                 &fs_info->ordered_bytes);
 608         }
 609 }
 610
 611 /*
 612  * Try to flush some data based on policy set by @state. This is only advisory
 613  * and may fail for various reasons. The caller is supposed to examine the
 614  * state of @space_info to detect the outcome.
 615  */
 616 static void flush_space(struct btrfs_fs_info *fs_info,
 617                        struct btrfs_space_info *space_info, u64 num_bytes,
 618                        enum btrfs_flush_state state, bool for_preempt)
 619 {
 620         struct btrfs_root *root = fs_info->extent_root;
 621         struct btrfs_trans_handle *trans;
 622         int nr;
 623         int ret = 0;
 624
 625         switch (state) {
 626         case FLUSH_DELAYED_ITEMS_NR:
 627         case FLUSH_DELAYED_ITEMS:
 628                 if (state == FLUSH_DELAYED_ITEMS_NR)
 629                         nr = calc_reclaim_items_nr(fs_info, num_bytes) * 2;
 630                 else
 631                         nr = -1;
 632
 633                 trans = btrfs_join_transaction(root);
 634                 if (IS_ERR(trans)) {
 635                         ret = PTR_ERR(trans);
 636                         break;
 637                 }
 638                 ret = btrfs_run_delayed_items_nr(trans, nr);
 639                 btrfs_end_transaction(trans);
 640                 break;
 641         case FLUSH_DELALLOC:
 642         case FLUSH_DELALLOC_WAIT:
 643         case FLUSH_DELALLOC_FULL:
 644                 if (state == FLUSH_DELALLOC_FULL)
 645                         num_bytes = U64_MAX;
 646                 shrink_delalloc(fs_info, space_info, num_bytes,
 647                                 state != FLUSH_DELALLOC, for_preempt);
 648                 break;
 649         case FLUSH_DELAYED_REFS_NR:
 650         case FLUSH_DELAYED_REFS:
 651                 trans = btrfs_join_transaction(root);
 652                 if (IS_ERR(trans)) {
 653                         ret = PTR_ERR(trans);
 654                         break;
 655                 }
 656                 if (state == FLUSH_DELAYED_REFS_NR)
 657                         nr = calc_reclaim_items_nr(fs_info, num_bytes);
 658                 else
 659                         nr = 0;
 660                 btrfs_run_delayed_refs(trans, nr);
 661                 btrfs_end_transaction(trans);
 662                 break;
 663         case ALLOC_CHUNK:
 664         case ALLOC_CHUNK_FORCE:
 665                 trans = btrfs_join_transaction(root);
 666                 if (IS_ERR(trans)) {
 667                         ret = PTR_ERR(trans);
 668                         break;
 669                 }
 670                 ret = btrfs_chunk_alloc(trans,
 671                                 btrfs_get_alloc_profile(fs_info, space_info->flags),
 672                                 (state == ALLOC_CHUNK) ? CHUNK_ALLOC_NO_FORCE :
 673                                         CHUNK_ALLOC_FORCE);
 674                 btrfs_end_transaction(trans);
 675                 if (ret > 0 || ret == -ENOSPC)
 676                         ret = 0;
 677                 break;
 678         case RUN_DELAYED_IPUTS:
 679                 /*
 680                  * If we have pending delayed iputs then we could free up a
 681                  * bunch of pinned space, so make sure we run the iputs before
 682                  * we do our pinned bytes check below.
 683                  */
 684                 btrfs_run_delayed_iputs(fs_info);
 685                 btrfs_wait_on_delayed_iputs(fs_info);
 686                 break;
 687         case COMMIT_TRANS:
 688                 ASSERT(current->journal_info == NULL);
 689                 trans = btrfs_join_transaction(root);
 690                 if (IS_ERR(trans)) {
 691                         ret = PTR_ERR(trans);
 692                         break;
 693                 }
 694                 ret = btrfs_commit_transaction(trans);
 695                 break;
 696         default:
 697                 ret = -ENOSPC;
 698                 break;
 699         }
 700
 701         trace_btrfs_flush_space(fs_info, space_info->flags, num_bytes, state,
 702                                 ret, for_preempt);
 703         return;
 704 }
 705
 706 static inline u64
 707 btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
 708                                  struct btrfs_space_info *space_info)
 709 {
 710         u64 used;
 711         u64 avail;
 712         u64 to_reclaim = space_info->reclaim_size;
 713
 714         lockdep_assert_held(&space_info->lock);
 715
 716         avail = calc_available_free_space(fs_info, space_info,
 717                                           BTRFS_RESERVE_FLUSH_ALL);
 718         used = btrfs_space_info_used(space_info, true);
 719
 720         /*
 721          * We may be flushing because suddenly we have less space than we had
 722          * before, and now we're well over-committed based on our current free
 723          * space.  If that's the case add in our overage so we make sure to put
 724          * appropriate pressure on the flushing state machine.
 725          */
 726         if (space_info->total_bytes + avail < used)
 727                 to_reclaim += used - (space_info->total_bytes + avail);
 728
 729         return to_reclaim;
 730 }
 731
 732 static bool need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
 733                                     struct btrfs_space_info *space_info)
 734 {
 735         u64 global_rsv_size = fs_info->global_block_rsv.reserved;
 736         u64 ordered, delalloc;
 737         u64 thresh = div_factor_fine(space_info->total_bytes, 90);
 738         u64 used;
 739
 740         /* If we're just plain full then async reclaim just slows us down. */
 741         if ((space_info->bytes_used + space_info->bytes_reserved +
 742              global_rsv_size) >= thresh)
 743                 return false;
 744
 745         used = space_info->bytes_may_use + space_info->bytes_pinned;
 746
 747         /* The total flushable belongs to the global rsv, don't flush. */
 748         if (global_rsv_size >= used)
 749                 return false;
 750
 751         /*
 752          * 128MiB is 1/4 of the maximum global rsv size.  If we have less than
 753          * that devoted to other reservations then there's no sense in flushing,
 754          * we don't have a lot of things that need flushing.
 755          */
 756         if (used - global_rsv_size <= SZ_128M)
 757                 return false;
 758
 759         /*
 760          * We have tickets queued, bail so we don't compete with the async
 761          * flushers.
 762          */
 763         if (space_info->reclaim_size)
 764                 return false;
 765
 766         /*
 767          * If we have over half of the free space occupied by reservations or
 768          * pinned then we want to start flushing.
 769          *
 770          * We do not do the traditional thing here, which is to say
 771          *
 772          *   if (used >= ((total_bytes + avail) / 2))
 773          *     return 1;
 774          *
 775          * because this doesn't quite work how we want.  If we had more than 50%
 776          * of the space_info used by bytes_used and we had 0 available we'd just
 777          * constantly run the background flusher.  Instead we want it to kick in
 778          * if our reclaimable space exceeds our clamped free space.
 779          *
 780          * Our clamping range is 2^1 -> 2^8.  Practically speaking that means
 781          * the following:
 782          *
 783          * Amount of RAM        Minimum threshold       Maximum threshold
 784          *
 785          *        256GiB                     1GiB                  128GiB
 786          *        128GiB                   512MiB                   64GiB
 787          *         64GiB                   256MiB                   32GiB
 788          *         32GiB                   128MiB                   16GiB
 789          *         16GiB                    64MiB                    8GiB
 790          *
 791          * These are the range our thresholds will fall in, corresponding to how
 792          * much delalloc we need for the background flusher to kick in.
 793          */
 794
 795         thresh = calc_available_free_space(fs_info, space_info,
 796                                            BTRFS_RESERVE_FLUSH_ALL);
 797         used = space_info->bytes_used + space_info->bytes_reserved +
 798                space_info->bytes_readonly + global_rsv_size;
 799         if (used < space_info->total_bytes)
 800                 thresh += space_info->total_bytes - used;
 801         thresh >>= space_info->clamp;
 802
 803         used = space_info->bytes_pinned;
 804
 805         /*
 806          * If we have more ordered bytes than delalloc bytes then we're either
 807          * doing a lot of DIO, or we simply don't have a lot of delalloc waiting
 808          * around.  Preemptive flushing is only useful in that it can free up
 809          * space before tickets need to wait for things to finish.  In the case
 810          * of ordered extents, preemptively waiting on ordered extents gets us
 811          * nothing, if our reservations are tied up in ordered extents we'll
 812          * simply have to slow down writers by forcing them to wait on ordered
 813          * extents.
 814          *
 815          * In the case that ordered is larger than delalloc, only include the
 816          * block reserves that we would actually be able to directly reclaim
 817          * from.  In this case if we're heavy on metadata operations this will
 818          * clearly be heavy enough to warrant preemptive flushing.  In the case
 819          * of heavy DIO or ordered reservations, preemptive flushing will just
 820          * waste time and cause us to slow down.
 821          *
 822          * We want to make sure we truly are maxed out on ordered however, so
 823          * cut ordered in half, and if it's still higher than delalloc then we
 824          * can keep flushing.  This is to avoid the case where we start
 825          * flushing, and now delalloc == ordered and we stop preemptively
 826          * flushing when we could still have several gigs of delalloc to flush.
 827          */
 828         ordered = percpu_counter_read_positive(&fs_info->ordered_bytes) >> 1;
 829         delalloc = percpu_counter_read_positive(&fs_info->delalloc_bytes);
 830         if (ordered >= delalloc)
 831                 used += fs_info->delayed_refs_rsv.reserved +
 832                         fs_info->delayed_block_rsv.reserved;
 833         else
 834                 used += space_info->bytes_may_use - global_rsv_size;
 835
 836         return (used >= thresh && !btrfs_fs_closing(fs_info) &&
 837                 !test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
 838 }
 839
 840 static bool steal_from_global_rsv(struct btrfs_fs_info *fs_info,
 841                                   struct btrfs_space_info *space_info,
 842                                   struct reserve_ticket *ticket)
 843 {
 844         struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
 845         u64 min_bytes;
 846
 847         if (global_rsv->space_info != space_info)
 848                 return false;
 849
 850         spin_lock(&global_rsv->lock);
 851         min_bytes = div_factor(global_rsv->size, 1);
 852         if (global_rsv->reserved < min_bytes + ticket->bytes) {
 853                 spin_unlock(&global_rsv->lock);
 854                 return false;
 855         }
 856         global_rsv->reserved -= ticket->bytes;
 857         remove_ticket(space_info, ticket);
 858         ticket->bytes = 0;
 859         wake_up(&ticket->wait);
 860         space_info->tickets_id++;
 861         if (global_rsv->reserved < global_rsv->size)
 862                 global_rsv->full = 0;
 863         spin_unlock(&global_rsv->lock);
 864
 865         return true;
 866 }
 867
 868 /*
 869  * maybe_fail_all_tickets - we've exhausted our flushing, start failing tickets
 870  * @fs_info - fs_info for this fs
 871  * @space_info - the space info we were flushing
 872  *
 873  * We call this when we've exhausted our flushing ability and haven't made
 874  * progress in satisfying tickets.  The reservation code handles tickets in
 875  * order, so if there is a large ticket first and then smaller ones we could
 876  * very well satisfy the smaller tickets.  This will attempt to wake up any
 877  * tickets in the list to catch this case.
 878  *
 879  * This function returns true if it was able to make progress by clearing out
 880  * other tickets, or if it stumbles across a ticket that was smaller than the
 881  * first ticket.
 882  */
 883 static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
 884                                    struct btrfs_space_info *space_info)
 885 {
 886         struct reserve_ticket *ticket;
 887         u64 tickets_id = space_info->tickets_id;
 888
 889         trace_btrfs_fail_all_tickets(fs_info, space_info);
 890
 891         if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
 892                 btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
 893                 __btrfs_dump_space_info(fs_info, space_info);
 894         }
 895
 896         while (!list_empty(&space_info->tickets) &&
 897                tickets_id == space_info->tickets_id) {
 898                 ticket = list_first_entry(&space_info->tickets,
 899                                           struct reserve_ticket, list);
 900
 901                 if (ticket->steal &&
 902                     steal_from_global_rsv(fs_info, space_info, ticket))
 903                         return true;
 904
 905                 if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
 906                         btrfs_info(fs_info, "failing ticket with %llu bytes",
 907                                    ticket->bytes);
 908
 909                 remove_ticket(space_info, ticket);
 910                 ticket->error = -ENOSPC;
 911                 wake_up(&ticket->wait);
 912
 913                 /*
 914                  * We're just throwing tickets away, so more flushing may not
 915                  * trip over btrfs_try_granting_tickets, so we need to call it
 916                  * here to see if we can make progress with the next ticket in
 917                  * the list.
 918                  */
 919                 btrfs_try_granting_tickets(fs_info, space_info);
 920         }
 921         return (tickets_id != space_info->tickets_id);
 922 }
 923
 924 /*
 925  * This is for normal flushers, we can wait all goddamned day if we want to.  We
 926  * will loop and continuously try to flush as long as we are making progress.
 927  * We count progress as clearing off tickets each time we have to loop.
 928  */
 929 static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 930 {
 931         struct btrfs_fs_info *fs_info;
 932         struct btrfs_space_info *space_info;
 933         u64 to_reclaim;
 934         enum btrfs_flush_state flush_state;
 935         int commit_cycles = 0;
 936         u64 last_tickets_id;
 937
 938         fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
 939         space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 940
 941         spin_lock(&space_info->lock);
 942         to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
 943         if (!to_reclaim) {
 944                 space_info->flush = 0;
 945                 spin_unlock(&space_info->lock);
 946                 return;
 947         }
 948         last_tickets_id = space_info->tickets_id;
 949         spin_unlock(&space_info->lock);
 950
 951         flush_state = FLUSH_DELAYED_ITEMS_NR;
 952         do {
 953                 flush_space(fs_info, space_info, to_reclaim, flush_state, false);
 954                 spin_lock(&space_info->lock);
 955                 if (list_empty(&space_info->tickets)) {
 956                         space_info->flush = 0;
 957                         spin_unlock(&space_info->lock);
 958                         return;
 959                 }
 960                 to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
 961                                                               space_info);
 962                 if (last_tickets_id == space_info->tickets_id) {
 963                         flush_state++;
 964                 } else {
 965                         last_tickets_id = space_info->tickets_id;
 966                         flush_state = FLUSH_DELAYED_ITEMS_NR;
 967                         if (commit_cycles)
 968                                 commit_cycles--;
 969                 }
 970
 971                 /*
 972                  * We do not want to empty the system of delalloc unless we're
 973                  * under heavy pressure, so allow one trip through the flushing
 974                  * logic before we start doing a FLUSH_DELALLOC_FULL.
 975                  */
 976                 if (flush_state == FLUSH_DELALLOC_FULL && !commit_cycles)
 977                         flush_state++;
 978
 979                 /*
 980                  * We don't want to force a chunk allocation until we've tried
 981                  * pretty hard to reclaim space.  Think of the case where we
 982                  * freed up a bunch of space and so have a lot of pinned space
 983                  * to reclaim.  We would rather use that than possibly create a
 984                  * underutilized metadata chunk.  So if this is our first run
 985                  * through the flushing state machine skip ALLOC_CHUNK_FORCE and
 986                  * commit the transaction.  If nothing has changed the next go
 987                  * around then we can force a chunk allocation.
 988                  */
 989                 if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
 990                         flush_state++;
 991
 992                 if (flush_state > COMMIT_TRANS) {
 993                         commit_cycles++;
 994                         if (commit_cycles > 2) {
 995                                 if (maybe_fail_all_tickets(fs_info, space_info)) {
 996                                         flush_state = FLUSH_DELAYED_ITEMS_NR;
 997                                         commit_cycles--;
 998                                 } else {
 999                                         space_info->flush = 0;
1000                                 }
1001                         } else {
1002                                 flush_state = FLUSH_DELAYED_ITEMS_NR;
1003                         }
1004                 }
1005                 spin_unlock(&space_info->lock);
1006         } while (flush_state <= COMMIT_TRANS);
1007 }
1008
1009 /*
1010  * This handles pre-flushing of metadata space before we get to the point that
1011  * we need to start blocking threads on tickets.  The logic here is different
1012  * from the other flush paths because it doesn't rely on tickets to tell us how
1013  * much we need to flush, instead it attempts to keep us below the 80% full
1014  * watermark of space by flushing whichever reservation pool is currently the
1015  * largest.
1016  */
1017 static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
1018 {
1019         struct btrfs_fs_info *fs_info;
1020         struct btrfs_space_info *space_info;
1021         struct btrfs_block_rsv *delayed_block_rsv;
1022         struct btrfs_block_rsv *delayed_refs_rsv;
1023         struct btrfs_block_rsv *global_rsv;
1024         struct btrfs_block_rsv *trans_rsv;
1025         int loops = 0;
1026
1027         fs_info = container_of(work, struct btrfs_fs_info,
1028                                preempt_reclaim_work);
1029         space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
1030         delayed_block_rsv = &fs_info->delayed_block_rsv;
1031         delayed_refs_rsv = &fs_info->delayed_refs_rsv;
1032         global_rsv = &fs_info->global_block_rsv;
1033         trans_rsv = &fs_info->trans_block_rsv;
1034
1035         spin_lock(&space_info->lock);
1036         while (need_preemptive_reclaim(fs_info, space_info)) {
1037                 enum btrfs_flush_state flush;
1038                 u64 delalloc_size = 0;
1039                 u64 to_reclaim, block_rsv_size;
1040                 u64 global_rsv_size = global_rsv->reserved;
1041
1042                 loops++;
1043
1044                 /*
1045                  * We don't have a precise counter for the metadata being
1046                  * reserved for delalloc, so we'll approximate it by subtracting
1047                  * out the block rsv's space from the bytes_may_use.  If that
1048                  * amount is higher than the individual reserves, then we can
1049                  * assume it's tied up in delalloc reservations.
1050                  */
1051                 block_rsv_size = global_rsv_size +
1052                         delayed_block_rsv->reserved +
1053                         delayed_refs_rsv->reserved +
1054                         trans_rsv->reserved;
1055                 if (block_rsv_size < space_info->bytes_may_use)
1056                         delalloc_size = space_info->bytes_may_use - block_rsv_size;
1057                 spin_unlock(&space_info->lock);
1058
1059                 /*
1060                  * We don't want to include the global_rsv in our calculation,
1061                  * because that's space we can't touch.  Subtract it from the
1062                  * block_rsv_size for the next checks.
1063                  */
1064                 block_rsv_size -= global_rsv_size;
1065
1066                 /*
1067                  * We really want to avoid flushing delalloc too much, as it
1068                  * could result in poor allocation patterns, so only flush it if
1069                  * it's larger than the rest of the pools combined.
1070                  */
1071                 if (delalloc_size > block_rsv_size) {
1072                         to_reclaim = delalloc_size;
1073                         flush = FLUSH_DELALLOC;
1074                 } else if (space_info->bytes_pinned >
1075                            (delayed_block_rsv->reserved +
1076                             delayed_refs_rsv->reserved)) {
1077                         to_reclaim = space_info->bytes_pinned;
1078                         flush = COMMIT_TRANS;
1079                 } else if (delayed_block_rsv->reserved >
1080                            delayed_refs_rsv->reserved) {
1081                         to_reclaim = delayed_block_rsv->reserved;
1082                         flush = FLUSH_DELAYED_ITEMS_NR;
1083                 } else {
1084                         to_reclaim = delayed_refs_rsv->reserved;
1085                         flush = FLUSH_DELAYED_REFS_NR;
1086                 }
1087
1088                 /*
1089                  * We don't want to reclaim everything, just a portion, so scale
1090                  * down the to_reclaim by 1/4.  If it takes us down to 0,
1091                  * reclaim 1 items worth.
1092                  */
1093                 to_reclaim >>= 2;
1094                 if (!to_reclaim)
1095                         to_reclaim = btrfs_calc_insert_metadata_size(fs_info, 1);
1096                 flush_space(fs_info, space_info, to_reclaim, flush, true);
1097                 cond_resched();
1098                 spin_lock(&space_info->lock);
1099         }
1100
1101         /* We only went through once, back off our clamping. */
1102         if (loops == 1 && !space_info->reclaim_size)
1103                 space_info->clamp = max(1, space_info->clamp - 1);
1104         trace_btrfs_done_preemptive_reclaim(fs_info, space_info);
1105         spin_unlock(&space_info->lock);
1106 }
1107
1108 /*
1109  * FLUSH_DELALLOC_WAIT:
1110  *   Space is freed from flushing delalloc in one of two ways.
1111  *
1112  *   1) compression is on and we allocate less space than we reserved
1113  *   2) we are overwriting existing space
1114  *
1115  *   For #1 that extra space is reclaimed as soon as the delalloc pages are
1116  *   COWed, by way of btrfs_add_reserved_bytes() which adds the actual extent
1117  *   length to ->bytes_reserved, and subtracts the reserved space from
1118  *   ->bytes_may_use.
1119  *
1120  *   For #2 this is trickier.  Once the ordered extent runs we will drop the
1121  *   extent in the range we are overwriting, which creates a delayed ref for
1122  *   that freed extent.  This however is not reclaimed until the transaction
1123  *   commits, thus the next stages.
1124  *
1125  * RUN_DELAYED_IPUTS
1126  *   If we are freeing inodes, we want to make sure all delayed iputs have
1127  *   completed, because they could have been on an inode with i_nlink == 0, and
1128  *   thus have been truncated and freed up space.  But again this space is not
1129  *   immediately re-usable, it comes in the form of a delayed ref, which must be
1130  *   run and then the transaction must be committed.
1131  *
1132  * COMMIT_TRANS
1133  *   This is where we reclaim all of the pinned space generated by running the
1134  *   iputs
1135  *
1136  * ALLOC_CHUNK_FORCE
1137  *   For data we start with alloc chunk force, however we could have been full
1138  *   before, and then the transaction commit could have freed new block groups,
1139  *   so if we now have space to allocate do the force chunk allocation.
1140  */
1141 static const enum btrfs_flush_state data_flush_states[] = {
1142         FLUSH_DELALLOC_FULL,
1143         RUN_DELAYED_IPUTS,
1144         COMMIT_TRANS,
1145         ALLOC_CHUNK_FORCE,
1146 };
1147
1148 static void btrfs_async_reclaim_data_space(struct work_struct *work)
1149 {
1150         struct btrfs_fs_info *fs_info;
1151         struct btrfs_space_info *space_info;
1152         u64 last_tickets_id;
1153         enum btrfs_flush_state flush_state = 0;
1154
1155         fs_info = container_of(work, struct btrfs_fs_info, async_data_reclaim_work);
1156         space_info = fs_info->data_sinfo;
1157
1158         spin_lock(&space_info->lock);
1159         if (list_empty(&space_info->tickets)) {
1160                 space_info->flush = 0;
1161                 spin_unlock(&space_info->lock);
1162                 return;
1163         }
1164         last_tickets_id = space_info->tickets_id;
1165         spin_unlock(&space_info->lock);
1166
1167         while (!space_info->full) {
1168                 flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
1169                 spin_lock(&space_info->lock);
1170                 if (list_empty(&space_info->tickets)) {
1171                         space_info->flush = 0;
1172                         spin_unlock(&space_info->lock);
1173                         return;
1174                 }
1175                 last_tickets_id = space_info->tickets_id;
1176                 spin_unlock(&space_info->lock);
1177         }
1178
1179         while (flush_state < ARRAY_SIZE(data_flush_states)) {
1180                 flush_space(fs_info, space_info, U64_MAX,
1181                             data_flush_states[flush_state], false);
1182                 spin_lock(&space_info->lock);
1183                 if (list_empty(&space_info->tickets)) {
1184                         space_info->flush = 0;
1185                         spin_unlock(&space_info->lock);
1186                         return;
1187                 }
1188
1189                 if (last_tickets_id == space_info->tickets_id) {
1190                         flush_state++;
1191                 } else {
1192                         last_tickets_id = space_info->tickets_id;
1193                         flush_state = 0;
1194                 }
1195
1196                 if (flush_state >= ARRAY_SIZE(data_flush_states)) {
1197                         if (space_info->full) {
1198                                 if (maybe_fail_all_tickets(fs_info, space_info))
1199                                         flush_state = 0;
1200                                 else
1201                                         space_info->flush = 0;
1202                         } else {
1203                                 flush_state = 0;
1204                         }
1205                 }
1206                 spin_unlock(&space_info->lock);
1207         }
1208 }
1209
1210 void btrfs_init_async_reclaim_work(struct btrfs_fs_info *fs_info)
1211 {
1212         INIT_WORK(&fs_info->async_reclaim_work, btrfs_async_reclaim_metadata_space);
1213         INIT_WORK(&fs_info->async_data_reclaim_work, btrfs_async_reclaim_data_space);
1214         INIT_WORK(&fs_info->preempt_reclaim_work,
1215                   btrfs_preempt_reclaim_metadata_space);
1216 }
1217
1218 static const enum btrfs_flush_state priority_flush_states[] = {
1219         FLUSH_DELAYED_ITEMS_NR,
1220         FLUSH_DELAYED_ITEMS,
1221         ALLOC_CHUNK,
1222 };
1223
1224 static const enum btrfs_flush_state evict_flush_states[] = {
1225         FLUSH_DELAYED_ITEMS_NR,
1226         FLUSH_DELAYED_ITEMS,
1227         FLUSH_DELAYED_REFS_NR,
1228         FLUSH_DELAYED_REFS,
1229         FLUSH_DELALLOC,
1230         FLUSH_DELALLOC_WAIT,
1231         FLUSH_DELALLOC_FULL,
1232         ALLOC_CHUNK,
1233         COMMIT_TRANS,
1234 };
1235
1236 static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
1237                                 struct btrfs_space_info *space_info,
1238                                 struct reserve_ticket *ticket,
1239                                 const enum btrfs_flush_state *states,
1240                                 int states_nr)
1241 {
1242         u64 to_reclaim;
1243         int flush_state;
1244
1245         spin_lock(&space_info->lock);
1246         to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
1247         if (!to_reclaim) {
1248                 spin_unlock(&space_info->lock);
1249                 return;
1250         }
1251         spin_unlock(&space_info->lock);
1252
1253         flush_state = 0;
1254         do {
1255                 flush_space(fs_info, space_info, to_reclaim, states[flush_state],
1256                             false);
1257                 flush_state++;
1258                 spin_lock(&space_info->lock);
1259                 if (ticket->bytes == 0) {
1260                         spin_unlock(&space_info->lock);
1261                         return;
1262                 }
1263                 spin_unlock(&space_info->lock);
1264         } while (flush_state < states_nr);
1265 }
1266
1267 static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
1268                                         struct btrfs_space_info *space_info,
1269                                         struct reserve_ticket *ticket)
1270 {
1271         while (!space_info->full) {
1272                 flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
1273                 spin_lock(&space_info->lock);
1274                 if (ticket->bytes == 0) {
1275                         spin_unlock(&space_info->lock);
1276                         return;
1277                 }
1278                 spin_unlock(&space_info->lock);
1279         }
1280 }
1281
1282 static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
1283                                 struct btrfs_space_info *space_info,
1284                                 struct reserve_ticket *ticket)
1285
1286 {
1287         DEFINE_WAIT(wait);
1288         int ret = 0;
1289
1290         spin_lock(&space_info->lock);
1291         while (ticket->bytes > 0 && ticket->error == 0) {
1292                 ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
1293                 if (ret) {
1294                         /*
1295                          * Delete us from the list. After we unlock the space
1296                          * info, we don't want the async reclaim job to reserve
1297                          * space for this ticket. If that would happen, then the
1298                          * ticket's task would not known that space was reserved
1299                          * despite getting an error, resulting in a space leak
1300                          * (bytes_may_use counter of our space_info).
1301                          */
1302                         remove_ticket(space_info, ticket);
1303                         ticket->error = -EINTR;
1304                         break;
1305                 }
1306                 spin_unlock(&space_info->lock);
1307
1308                 schedule();
1309
1310                 finish_wait(&ticket->wait, &wait);
1311                 spin_lock(&space_info->lock);
1312         }
1313         spin_unlock(&space_info->lock);
1314 }
1315
1316 /**
1317  * Do the appropriate flushing and waiting for a ticket
1318  *
1319  * @fs_info:    the filesystem
1320  * @space_info: space info for the reservation
1321  * @ticket:     ticket for the reservation
1322  * @start_ns:   timestamp when the reservation started
1323  * @orig_bytes: amount of bytes originally reserved
1324  * @flush:      how much we can flush
1325  *
1326  * This does the work of figuring out how to flush for the ticket, waiting for
1327  * the reservation, and returning the appropriate error if there is one.
1328  */
1329 static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
1330                                  struct btrfs_space_info *space_info,
1331                                  struct reserve_ticket *ticket,
1332                                  u64 start_ns, u64 orig_bytes,
1333                                  enum btrfs_reserve_flush_enum flush)
1334 {
1335         int ret;
1336
1337         switch (flush) {
1338         case BTRFS_RESERVE_FLUSH_DATA:
1339         case BTRFS_RESERVE_FLUSH_ALL:
1340         case BTRFS_RESERVE_FLUSH_ALL_STEAL:
1341                 wait_reserve_ticket(fs_info, space_info, ticket);
1342                 break;
1343         case BTRFS_RESERVE_FLUSH_LIMIT:
1344                 priority_reclaim_metadata_space(fs_info, space_info, ticket,
1345                                                 priority_flush_states,
1346                                                 ARRAY_SIZE(priority_flush_states));
1347                 break;
1348         case BTRFS_RESERVE_FLUSH_EVICT:
1349                 priority_reclaim_metadata_space(fs_info, space_info, ticket,
1350                                                 evict_flush_states,
1351                                                 ARRAY_SIZE(evict_flush_states));
1352                 break;
1353         case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
1354                 priority_reclaim_data_space(fs_info, space_info, ticket);
1355                 break;
1356         default:
1357                 ASSERT(0);
1358                 break;
1359         }
1360
1361         spin_lock(&space_info->lock);
1362         ret = ticket->error;
1363         if (ticket->bytes || ticket->error) {
1364                 /*
1365                  * We were a priority ticket, so we need to delete ourselves
1366                  * from the list.  Because we could have other priority tickets
1367                  * behind us that require less space, run
1368                  * btrfs_try_granting_tickets() to see if their reservations can
1369                  * now be made.
1370                  */
1371                 if (!list_empty(&ticket->list)) {
1372                         remove_ticket(space_info, ticket);
1373                         btrfs_try_granting_tickets(fs_info, space_info);
1374                 }
1375
1376                 if (!ret)
1377                         ret = -ENOSPC;
1378         }
1379         spin_unlock(&space_info->lock);
1380         ASSERT(list_empty(&ticket->list));
1381         /*
1382          * Check that we can't have an error set if the reservation succeeded,
1383          * as that would confuse tasks and lead them to error out without
1384          * releasing reserved space (if an error happens the expectation is that
1385          * space wasn't reserved at all).
1386          */
1387         ASSERT(!(ticket->bytes == 0 && ticket->error));
1388         trace_btrfs_reserve_ticket(fs_info, space_info->flags, orig_bytes,
1389                                    start_ns, flush, ticket->error);
1390         return ret;
1391 }
1392
1393 /*
1394  * This returns true if this flush state will go through the ordinary flushing
1395  * code.
1396  */
1397 static inline bool is_normal_flushing(enum btrfs_reserve_flush_enum flush)
1398 {
1399         return  (flush == BTRFS_RESERVE_FLUSH_ALL) ||
1400                 (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
1401 }
1402
1403 static inline void maybe_clamp_preempt(struct btrfs_fs_info *fs_info,
1404                                        struct btrfs_space_info *space_info)
1405 {
1406         u64 ordered = percpu_counter_sum_positive(&fs_info->ordered_bytes);
1407         u64 delalloc = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
1408
1409         /*
1410          * If we're heavy on ordered operations then clamping won't help us.  We
1411          * need to clamp specifically to keep up with dirty'ing buffered
1412          * writers, because there's not a 1:1 correlation of writing delalloc
1413          * and freeing space, like there is with flushing delayed refs or
1414          * delayed nodes.  If we're already more ordered than delalloc then
1415          * we're keeping up, otherwise we aren't and should probably clamp.
1416          */
1417         if (ordered < delalloc)
1418                 space_info->clamp = min(space_info->clamp + 1, 8);
1419 }
1420
1421 /**
1422  * Try to reserve bytes from the block_rsv's space
1423  *
1424  * @fs_info:    the filesystem
1425  * @space_info: space info we want to allocate from
1426  * @orig_bytes: number of bytes we want
1427  * @flush:      whether or not we can flush to make our reservation
1428  *
1429  * This will reserve orig_bytes number of bytes from the space info associated
1430  * with the block_rsv.  If there is not enough space it will make an attempt to
1431  * flush out space to make room.  It will do this by flushing delalloc if
1432  * possible or committing the transaction.  If flush is 0 then no attempts to
1433  * regain reservations will be made and this will fail if there is not enough
1434  * space already.
1435  */
1436 static int __reserve_bytes(struct btrfs_fs_info *fs_info,
1437                            struct btrfs_space_info *space_info, u64 orig_bytes,
1438                            enum btrfs_reserve_flush_enum flush)
1439 {
1440         struct work_struct *async_work;
1441         struct reserve_ticket ticket;
1442         u64 start_ns = 0;
1443         u64 used;
1444         int ret = 0;
1445         bool pending_tickets;
1446
1447         ASSERT(orig_bytes);
1448         ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
1449
1450         if (flush == BTRFS_RESERVE_FLUSH_DATA)
1451                 async_work = &fs_info->async_data_reclaim_work;
1452         else
1453                 async_work = &fs_info->async_reclaim_work;
1454
1455         spin_lock(&space_info->lock);
1456         ret = -ENOSPC;
1457         used = btrfs_space_info_used(space_info, true);
1458
1459         /*
1460          * We don't want NO_FLUSH allocations to jump everybody, they can
1461          * generally handle ENOSPC in a different way, so treat them the same as
1462          * normal flushers when it comes to skipping pending tickets.
1463          */
1464         if (is_normal_flushing(flush) || (flush == BTRFS_RESERVE_NO_FLUSH))
1465                 pending_tickets = !list_empty(&space_info->tickets) ||
1466                         !list_empty(&space_info->priority_tickets);
1467         else
1468                 pending_tickets = !list_empty(&space_info->priority_tickets);
1469
1470         /*
1471          * Carry on if we have enough space (short-circuit) OR call
1472          * can_overcommit() to ensure we can overcommit to continue.
1473          */
1474         if (!pending_tickets &&
1475             ((used + orig_bytes <= space_info->total_bytes) ||
1476              btrfs_can_overcommit(fs_info, space_info, orig_bytes, flush))) {
1477                 btrfs_space_info_update_bytes_may_use(fs_info, space_info,
1478                                                       orig_bytes);
1479                 ret = 0;
1480         }
1481
1482         /*
1483          * If we couldn't make a reservation then setup our reservation ticket
1484          * and kick the async worker if it's not already running.
1485          *
1486          * If we are a priority flusher then we just need to add our ticket to
1487          * the list and we will do our own flushing further down.
1488          */
1489         if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
1490                 ticket.bytes = orig_bytes;
1491                 ticket.error = 0;
1492                 space_info->reclaim_size += ticket.bytes;
1493                 init_waitqueue_head(&ticket.wait);
1494                 ticket.steal = (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
1495                 if (trace_btrfs_reserve_ticket_enabled())
1496                         start_ns = ktime_get_ns();
1497
1498                 if (flush == BTRFS_RESERVE_FLUSH_ALL ||
1499                     flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
1500                     flush == BTRFS_RESERVE_FLUSH_DATA) {
1501                         list_add_tail(&ticket.list, &space_info->tickets);
1502                         if (!space_info->flush) {
1503                                 /*
1504                                  * We were forced to add a reserve ticket, so
1505                                  * our preemptive flushing is unable to keep
1506                                  * up.  Clamp down on the threshold for the
1507                                  * preemptive flushing in order to keep up with
1508                                  * the workload.
1509                                  */
1510                                 maybe_clamp_preempt(fs_info, space_info);
1511
1512                                 space_info->flush = 1;
1513                                 trace_btrfs_trigger_flush(fs_info,
1514                                                           space_info->flags,
1515                                                           orig_bytes, flush,
1516                                                           "enospc");
1517                                 queue_work(system_unbound_wq, async_work);
1518                         }
1519                 } else {
1520                         list_add_tail(&ticket.list,
1521                                       &space_info->priority_tickets);
1522                 }
1523         } else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
1524                 used += orig_bytes;
1525                 /*
1526                  * We will do the space reservation dance during log replay,
1527                  * which means we won't have fs_info->fs_root set, so don't do
1528                  * the async reclaim as we will panic.
1529                  */
1530                 if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
1531                     !work_busy(&fs_info->preempt_reclaim_work) &&
1532                     need_preemptive_reclaim(fs_info, space_info)) {
1533                         trace_btrfs_trigger_flush(fs_info, space_info->flags,
1534                                                   orig_bytes, flush, "preempt");
1535                         queue_work(system_unbound_wq,
1536                                    &fs_info->preempt_reclaim_work);
1537                 }
1538         }
1539         spin_unlock(&space_info->lock);
1540         if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
1541                 return ret;
1542
1543         return handle_reserve_ticket(fs_info, space_info, &ticket, start_ns,
1544                                      orig_bytes, flush);
1545 }
1546
1547 /**
1548  * Trye to reserve metadata bytes from the block_rsv's space
1549  *
1550  * @root:       the root we're allocating for
1551  * @block_rsv:  block_rsv we're allocating for
1552  * @orig_bytes: number of bytes we want
1553  * @flush:      whether or not we can flush to make our reservation
1554  *
1555  * This will reserve orig_bytes number of bytes from the space info associated
1556  * with the block_rsv.  If there is not enough space it will make an attempt to
1557  * flush out space to make room.  It will do this by flushing delalloc if
1558  * possible or committing the transaction.  If flush is 0 then no attempts to
1559  * regain reservations will be made and this will fail if there is not enough
1560  * space already.
1561  */
1562 int btrfs_reserve_metadata_bytes(struct btrfs_root *root,
1563                                  struct btrfs_block_rsv *block_rsv,
1564                                  u64 orig_bytes,
1565                                  enum btrfs_reserve_flush_enum flush)
1566 {
1567         struct btrfs_fs_info *fs_info = root->fs_info;
1568         struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
1569         int ret;
1570
1571         ret = __reserve_bytes(fs_info, block_rsv->space_info, orig_bytes, flush);
1572         if (ret == -ENOSPC &&
1573             unlikely(root->orphan_cleanup_state == ORPHAN_CLEANUP_STARTED)) {
1574                 if (block_rsv != global_rsv &&
1575                     !btrfs_block_rsv_use_bytes(global_rsv, orig_bytes))
1576                         ret = 0;
1577         }
1578         if (ret == -ENOSPC) {
1579                 trace_btrfs_space_reservation(fs_info, "space_info:enospc",
1580                                               block_rsv->space_info->flags,
1581                                               orig_bytes, 1);
1582
1583                 if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
1584                         btrfs_dump_space_info(fs_info, block_rsv->space_info,
1585                                               orig_bytes, 0);
1586         }
1587         return ret;
1588 }
1589
1590 /**
1591  * Try to reserve data bytes for an allocation
1592  *
1593  * @fs_info: the filesystem
1594  * @bytes:   number of bytes we need
1595  * @flush:   how we are allowed to flush
1596  *
1597  * This will reserve bytes from the data space info.  If there is not enough
1598  * space then we will attempt to flush space as specified by flush.
1599  */
1600 int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
1601                              enum btrfs_reserve_flush_enum flush)
1602 {
1603         struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
1604         int ret;
1605
1606         ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
1607                flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE);
1608         ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
1609
1610         ret = __reserve_bytes(fs_info, data_sinfo, bytes, flush);
1611         if (ret == -ENOSPC) {
1612                 trace_btrfs_space_reservation(fs_info, "space_info:enospc",
1613                                               data_sinfo->flags, bytes, 1);
1614                 if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
1615                         btrfs_dump_space_info(fs_info, data_sinfo, bytes, 0);
1616         }
1617         return ret;
1618 }