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  *     may_commit_transaction() is the ultimate arbiter on whether we commit the
 137  *     transaction or not.  In order to avoid constantly churning we do all the
 138  *     above flushing first and then commit the transaction as the last resort.
 139  *     However we need to take into account things like pinned space that would
 140  *     be freed, plus any delayed work we may not have gotten rid of in the case
 141  *     of metadata.
 142  *
 143  * OVERCOMMIT
 144  *
 145  *   Because we hold so many reservations for metadata we will allow you to
 146  *   reserve more space than is currently free in the currently allocate
 147  *   metadata space.  This only happens with metadata, data does not allow
 148  *   overcommitting.
 149  *
 150  *   You can see the current logic for when we allow overcommit in
 151  *   btrfs_can_overcommit(), but it only applies to unallocated space.  If there
 152  *   is no unallocated space to be had, all reservations are kept within the
 153  *   free space in the allocated metadata chunks.
 154  *
 155  *   Because of overcommitting, you generally want to use the
 156  *   btrfs_can_overcommit() logic for metadata allocations, as it does the right
 157  *   thing with or without extra unallocated space.
 158  */
 159
 160 u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
 161                           bool may_use_included)
 162 {
 163         ASSERT(s_info);
 164         return s_info->bytes_used + s_info->bytes_reserved +
 165                 s_info->bytes_pinned + s_info->bytes_readonly +
 166                 (may_use_included ? s_info->bytes_may_use : 0);
 167 }
 168
 169 /*
 170  * after adding space to the filesystem, we need to clear the full flags
 171  * on all the space infos.
 172  */
 173 void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
 174 {
 175         struct list_head *head = &info->space_info;
 176         struct btrfs_space_info *found;
 177
 178         rcu_read_lock();
 179         list_for_each_entry_rcu(found, head, list)
 180                 found->full = 0;
 181         rcu_read_unlock();
 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         ret = percpu_counter_init(&space_info->total_bytes_pinned, 0,
 196                                  GFP_KERNEL);
 197         if (ret) {
 198                 kfree(space_info);
 199                 return ret;
 200         }
 201
 202         for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
 203                 INIT_LIST_HEAD(&space_info->block_groups[i]);
 204         init_rwsem(&space_info->groups_sem);
 205         spin_lock_init(&space_info->lock);
 206         space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
 207         space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
 208         INIT_LIST_HEAD(&space_info->ro_bgs);
 209         INIT_LIST_HEAD(&space_info->tickets);
 210         INIT_LIST_HEAD(&space_info->priority_tickets);
 211
 212         ret = btrfs_sysfs_add_space_info_type(info, space_info);
 213         if (ret)
 214                 return ret;
 215
 216         list_add_rcu(&space_info->list, &info->space_info);
 217         if (flags & BTRFS_BLOCK_GROUP_DATA)
 218                 info->data_sinfo = space_info;
 219
 220         return ret;
 221 }
 222
 223 int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 224 {
 225         struct btrfs_super_block *disk_super;
 226         u64 features;
 227         u64 flags;
 228         int mixed = 0;
 229         int ret;
 230
 231         disk_super = fs_info->super_copy;
 232         if (!btrfs_super_root(disk_super))
 233                 return -EINVAL;
 234
 235         features = btrfs_super_incompat_flags(disk_super);
 236         if (features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
 237                 mixed = 1;
 238
 239         flags = BTRFS_BLOCK_GROUP_SYSTEM;
 240         ret = create_space_info(fs_info, flags);
 241         if (ret)
 242                 goto out;
 243
 244         if (mixed) {
 245                 flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
 246                 ret = create_space_info(fs_info, flags);
 247         } else {
 248                 flags = BTRFS_BLOCK_GROUP_METADATA;
 249                 ret = create_space_info(fs_info, flags);
 250                 if (ret)
 251                         goto out;
 252
 253                 flags = BTRFS_BLOCK_GROUP_DATA;
 254                 ret = create_space_info(fs_info, flags);
 255         }
 256 out:
 257         return ret;
 258 }
 259
 260 void btrfs_update_space_info(struct btrfs_fs_info *info, u64 flags,
 261                              u64 total_bytes, u64 bytes_used,
 262                              u64 bytes_readonly,
 263                              struct btrfs_space_info **space_info)
 264 {
 265         struct btrfs_space_info *found;
 266         int factor;
 267
 268         factor = btrfs_bg_type_to_factor(flags);
 269
 270         found = btrfs_find_space_info(info, flags);
 271         ASSERT(found);
 272         spin_lock(&found->lock);
 273         found->total_bytes += total_bytes;
 274         found->disk_total += total_bytes * factor;
 275         found->bytes_used += bytes_used;
 276         found->disk_used += bytes_used * factor;
 277         found->bytes_readonly += bytes_readonly;
 278         if (total_bytes > 0)
 279                 found->full = 0;
 280         btrfs_try_granting_tickets(info, found);
 281         spin_unlock(&found->lock);
 282         *space_info = found;
 283 }
 284
 285 struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
 286                                                u64 flags)
 287 {
 288         struct list_head *head = &info->space_info;
 289         struct btrfs_space_info *found;
 290
 291         flags &= BTRFS_BLOCK_GROUP_TYPE_MASK;
 292
 293         rcu_read_lock();
 294         list_for_each_entry_rcu(found, head, list) {
 295                 if (found->flags & flags) {
 296                         rcu_read_unlock();
 297                         return found;
 298                 }
 299         }
 300         rcu_read_unlock();
 301         return NULL;
 302 }
 303
 304 static inline u64 calc_global_rsv_need_space(struct btrfs_block_rsv *global)
 305 {
 306         return (global->size << 1);
 307 }
 308
 309 static u64 calc_available_free_space(struct btrfs_fs_info *fs_info,
 310                           struct btrfs_space_info *space_info,
 311                           enum btrfs_reserve_flush_enum flush)
 312 {
 313         u64 profile;
 314         u64 avail;
 315         int factor;
 316
 317         if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
 318                 profile = btrfs_system_alloc_profile(fs_info);
 319         else
 320                 profile = btrfs_metadata_alloc_profile(fs_info);
 321
 322         avail = atomic64_read(&fs_info->free_chunk_space);
 323
 324         /*
 325          * If we have dup, raid1 or raid10 then only half of the free
 326          * space is actually usable.  For raid56, the space info used
 327          * doesn't include the parity drive, so we don't have to
 328          * change the math
 329          */
 330         factor = btrfs_bg_type_to_factor(profile);
 331         avail = div_u64(avail, factor);
 332
 333         /*
 334          * If we aren't flushing all things, let us overcommit up to
 335          * 1/2th of the space. If we can flush, don't let us overcommit
 336          * too much, let it overcommit up to 1/8 of the space.
 337          */
 338         if (flush == BTRFS_RESERVE_FLUSH_ALL)
 339                 avail >>= 3;
 340         else
 341                 avail >>= 1;
 342         return avail;
 343 }
 344
 345 int btrfs_can_overcommit(struct btrfs_fs_info *fs_info,
 346                          struct btrfs_space_info *space_info, u64 bytes,
 347                          enum btrfs_reserve_flush_enum flush)
 348 {
 349         u64 avail;
 350         u64 used;
 351
 352         /* Don't overcommit when in mixed mode */
 353         if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
 354                 return 0;
 355
 356         used = btrfs_space_info_used(space_info, true);
 357         avail = calc_available_free_space(fs_info, space_info, flush);
 358
 359         if (used + bytes < space_info->total_bytes + avail)
 360                 return 1;
 361         return 0;
 362 }
 363
 364 static void remove_ticket(struct btrfs_space_info *space_info,
 365                           struct reserve_ticket *ticket)
 366 {
 367         if (!list_empty(&ticket->list)) {
 368                 list_del_init(&ticket->list);
 369                 ASSERT(space_info->reclaim_size >= ticket->bytes);
 370                 space_info->reclaim_size -= ticket->bytes;
 371         }
 372 }
 373
 374 /*
 375  * This is for space we already have accounted in space_info->bytes_may_use, so
 376  * basically when we're returning space from block_rsv's.
 377  */
 378 void btrfs_try_granting_tickets(struct btrfs_fs_info *fs_info,
 379                                 struct btrfs_space_info *space_info)
 380 {
 381         struct list_head *head;
 382         enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;
 383
 384         lockdep_assert_held(&space_info->lock);
 385
 386         head = &space_info->priority_tickets;
 387 again:
 388         while (!list_empty(head)) {
 389                 struct reserve_ticket *ticket;
 390                 u64 used = btrfs_space_info_used(space_info, true);
 391
 392                 ticket = list_first_entry(head, struct reserve_ticket, list);
 393
 394                 /* Check and see if our ticket can be satisified now. */
 395                 if ((used + ticket->bytes <= space_info->total_bytes) ||
 396                     btrfs_can_overcommit(fs_info, space_info, ticket->bytes,
 397                                          flush)) {
 398                         btrfs_space_info_update_bytes_may_use(fs_info,
 399                                                               space_info,
 400                                                               ticket->bytes);
 401                         remove_ticket(space_info, ticket);
 402                         ticket->bytes = 0;
 403                         space_info->tickets_id++;
 404                         wake_up(&ticket->wait);
 405                 } else {
 406                         break;
 407                 }
 408         }
 409
 410         if (head == &space_info->priority_tickets) {
 411                 head = &space_info->tickets;
 412                 flush = BTRFS_RESERVE_FLUSH_ALL;
 413                 goto again;
 414         }
 415 }
 416
 417 #define DUMP_BLOCK_RSV(fs_info, rsv_name)                               \
 418 do {                                                                    \
 419         struct btrfs_block_rsv *__rsv = &(fs_info)->rsv_name;           \
 420         spin_lock(&__rsv->lock);                                        \
 421         btrfs_info(fs_info, #rsv_name ": size %llu reserved %llu",      \
 422                    __rsv->size, __rsv->reserved);                       \
 423         spin_unlock(&__rsv->lock);                                      \
 424 } while (0)
 425
 426 static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 427                                     struct btrfs_space_info *info)
 428 {
 429         lockdep_assert_held(&info->lock);
 430
 431         btrfs_info(fs_info, "space_info %llu has %llu free, is %sfull",
 432                    info->flags,
 433                    info->total_bytes - btrfs_space_info_used(info, true),
 434                    info->full ? "" : "not ");
 435         btrfs_info(fs_info,
 436                 "space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu",
 437                 info->total_bytes, info->bytes_used, info->bytes_pinned,
 438                 info->bytes_reserved, info->bytes_may_use,
 439                 info->bytes_readonly);
 440
 441         DUMP_BLOCK_RSV(fs_info, global_block_rsv);
 442         DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
 443         DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
 444         DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
 445         DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
 446
 447 }
 448
 449 void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
 450                            struct btrfs_space_info *info, u64 bytes,
 451                            int dump_block_groups)
 452 {
 453         struct btrfs_block_group *cache;
 454         int index = 0;
 455
 456         spin_lock(&info->lock);
 457         __btrfs_dump_space_info(fs_info, info);
 458         spin_unlock(&info->lock);
 459
 460         if (!dump_block_groups)
 461                 return;
 462
 463         down_read(&info->groups_sem);
 464 again:
 465         list_for_each_entry(cache, &info->block_groups[index], list) {
 466                 spin_lock(&cache->lock);
 467                 btrfs_info(fs_info,
 468                         "block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %s",
 469                         cache->start, cache->length, cache->used, cache->pinned,
 470                         cache->reserved, cache->ro ? "[readonly]" : "");
 471                 spin_unlock(&cache->lock);
 472                 btrfs_dump_free_space(cache, bytes);
 473         }
 474         if (++index < BTRFS_NR_RAID_TYPES)
 475                 goto again;
 476         up_read(&info->groups_sem);
 477 }
 478
 479 static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
 480                                         u64 to_reclaim)
 481 {
 482         u64 bytes;
 483         u64 nr;
 484
 485         bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
 486         nr = div64_u64(to_reclaim, bytes);
 487         if (!nr)
 488                 nr = 1;
 489         return nr;
 490 }
 491
 492 #define EXTENT_SIZE_PER_ITEM    SZ_256K
 493
 494 /*
 495  * shrink metadata reservation for delalloc
 496  */
 497 static void shrink_delalloc(struct btrfs_fs_info *fs_info,
 498                             struct btrfs_space_info *space_info,
 499                             u64 to_reclaim, bool wait_ordered)
 500 {
 501         struct btrfs_trans_handle *trans;
 502         u64 delalloc_bytes;
 503         u64 dio_bytes;
 504         u64 items;
 505         long time_left;
 506         int loops;
 507
 508         /* Calc the number of the pages we need flush for space reservation */
 509         if (to_reclaim == U64_MAX) {
 510                 items = U64_MAX;
 511         } else {
 512                 /*
 513                  * to_reclaim is set to however much metadata we need to
 514                  * reclaim, but reclaiming that much data doesn't really track
 515                  * exactly, so increase the amount to reclaim by 2x in order to
 516                  * make sure we're flushing enough delalloc to hopefully reclaim
 517                  * some metadata reservations.
 518                  */
 519                 items = calc_reclaim_items_nr(fs_info, to_reclaim) * 2;
 520                 to_reclaim = items * EXTENT_SIZE_PER_ITEM;
 521         }
 522
 523         trans = (struct btrfs_trans_handle *)current->journal_info;
 524
 525         delalloc_bytes = percpu_counter_sum_positive(
 526                                                 &fs_info->delalloc_bytes);
 527         dio_bytes = percpu_counter_sum_positive(&fs_info->dio_bytes);
 528         if (delalloc_bytes == 0 && dio_bytes == 0) {
 529                 if (trans)
 530                         return;
 531                 if (wait_ordered)
 532                         btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
 533                 return;
 534         }
 535
 536         /*
 537          * If we are doing more ordered than delalloc we need to just wait on
 538          * ordered extents, otherwise we'll waste time trying to flush delalloc
 539          * that likely won't give us the space back we need.
 540          */
 541         if (dio_bytes > delalloc_bytes)
 542                 wait_ordered = true;
 543
 544         loops = 0;
 545         while ((delalloc_bytes || dio_bytes) && loops < 3) {
 546                 btrfs_start_delalloc_roots(fs_info, items);
 547
 548                 loops++;
 549                 if (wait_ordered && !trans) {
 550                         btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
 551                 } else {
 552                         time_left = schedule_timeout_killable(1);
 553                         if (time_left)
 554                                 break;
 555                 }
 556
 557                 spin_lock(&space_info->lock);
 558                 if (list_empty(&space_info->tickets) &&
 559                     list_empty(&space_info->priority_tickets)) {
 560                         spin_unlock(&space_info->lock);
 561                         break;
 562                 }
 563                 spin_unlock(&space_info->lock);
 564
 565                 delalloc_bytes = percpu_counter_sum_positive(
 566                                                 &fs_info->delalloc_bytes);
 567                 dio_bytes = percpu_counter_sum_positive(&fs_info->dio_bytes);
 568         }
 569 }
 570
 571 /**
 572  * maybe_commit_transaction - possibly commit the transaction if its ok to
 573  * @root - the root we're allocating for
 574  * @bytes - the number of bytes we want to reserve
 575  * @force - force the commit
 576  *
 577  * This will check to make sure that committing the transaction will actually
 578  * get us somewhere and then commit the transaction if it does.  Otherwise it
 579  * will return -ENOSPC.
 580  */
 581 static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 582                                   struct btrfs_space_info *space_info,
 583                                   u64 bytes_needed)
 584 {
 585         struct reserve_ticket *ticket = NULL;
 586         struct btrfs_block_rsv *delayed_rsv = &fs_info->delayed_block_rsv;
 587         struct btrfs_block_rsv *delayed_refs_rsv = &fs_info->delayed_refs_rsv;
 588         struct btrfs_block_rsv *trans_rsv = &fs_info->trans_block_rsv;
 589         struct btrfs_trans_handle *trans;
 590         u64 reclaim_bytes = 0;
 591         u64 cur_free_bytes = 0;
 592         bool do_commit = false;
 593
 594         trans = (struct btrfs_trans_handle *)current->journal_info;
 595         if (trans)
 596                 return -EAGAIN;
 597
 598         /*
 599          * If we are data and have passed in U64_MAX we just want to
 600          * unconditionally commit the transaction to match the previous data
 601          * flushing behavior.
 602          */
 603         if ((space_info->flags & BTRFS_BLOCK_GROUP_DATA) &&
 604             bytes_needed == U64_MAX) {
 605                 do_commit = true;
 606                 goto check_pinned;
 607         }
 608
 609         spin_lock(&space_info->lock);
 610         cur_free_bytes = btrfs_space_info_used(space_info, true);
 611         if (cur_free_bytes < space_info->total_bytes)
 612                 cur_free_bytes = space_info->total_bytes - cur_free_bytes;
 613         else
 614                 cur_free_bytes = 0;
 615
 616         if (!list_empty(&space_info->priority_tickets))
 617                 ticket = list_first_entry(&space_info->priority_tickets,
 618                                           struct reserve_ticket, list);
 619         else if (!list_empty(&space_info->tickets))
 620                 ticket = list_first_entry(&space_info->tickets,
 621                                           struct reserve_ticket, list);
 622         if (ticket)
 623                 bytes_needed = ticket->bytes;
 624
 625         if (bytes_needed > cur_free_bytes)
 626                 bytes_needed -= cur_free_bytes;
 627         else
 628                 bytes_needed = 0;
 629         spin_unlock(&space_info->lock);
 630
 631         if (!bytes_needed)
 632                 return 0;
 633
 634 check_pinned:
 635         trans = btrfs_join_transaction(fs_info->extent_root);
 636         if (IS_ERR(trans))
 637                 return PTR_ERR(trans);
 638
 639         /*
 640          * See if there is enough pinned space to make this reservation, or if
 641          * we have block groups that are going to be freed, allowing us to
 642          * possibly do a chunk allocation the next loop through.
 643          */
 644         if (do_commit ||
 645             test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags) ||
 646             __percpu_counter_compare(&space_info->total_bytes_pinned,
 647                                      bytes_needed,
 648                                      BTRFS_TOTAL_BYTES_PINNED_BATCH) >= 0)
 649                 goto commit;
 650
 651         /*
 652          * See if there is some space in the delayed insertion reserve for this
 653          * reservation.  If the space_info's don't match (like for DATA or
 654          * SYSTEM) then just go enospc, reclaiming this space won't recover any
 655          * space to satisfy those reservations.
 656          */
 657         if (space_info != delayed_rsv->space_info)
 658                 goto enospc;
 659
 660         spin_lock(&delayed_rsv->lock);
 661         reclaim_bytes += delayed_rsv->reserved;
 662         spin_unlock(&delayed_rsv->lock);
 663
 664         spin_lock(&delayed_refs_rsv->lock);
 665         reclaim_bytes += delayed_refs_rsv->reserved;
 666         spin_unlock(&delayed_refs_rsv->lock);
 667
 668         spin_lock(&trans_rsv->lock);
 669         reclaim_bytes += trans_rsv->reserved;
 670         spin_unlock(&trans_rsv->lock);
 671
 672         if (reclaim_bytes >= bytes_needed)
 673                 goto commit;
 674         bytes_needed -= reclaim_bytes;
 675
 676         if (__percpu_counter_compare(&space_info->total_bytes_pinned,
 677                                    bytes_needed,
 678                                    BTRFS_TOTAL_BYTES_PINNED_BATCH) < 0)
 679                 goto enospc;
 680
 681 commit:
 682         return btrfs_commit_transaction(trans);
 683 enospc:
 684         btrfs_end_transaction(trans);
 685         return -ENOSPC;
 686 }
 687
 688 /*
 689  * Try to flush some data based on policy set by @state. This is only advisory
 690  * and may fail for various reasons. The caller is supposed to examine the
 691  * state of @space_info to detect the outcome.
 692  */
 693 static void flush_space(struct btrfs_fs_info *fs_info,
 694                        struct btrfs_space_info *space_info, u64 num_bytes,
 695                        int state)
 696 {
 697         struct btrfs_root *root = fs_info->extent_root;
 698         struct btrfs_trans_handle *trans;
 699         int nr;
 700         int ret = 0;
 701
 702         switch (state) {
 703         case FLUSH_DELAYED_ITEMS_NR:
 704         case FLUSH_DELAYED_ITEMS:
 705                 if (state == FLUSH_DELAYED_ITEMS_NR)
 706                         nr = calc_reclaim_items_nr(fs_info, num_bytes) * 2;
 707                 else
 708                         nr = -1;
 709
 710                 trans = btrfs_join_transaction(root);
 711                 if (IS_ERR(trans)) {
 712                         ret = PTR_ERR(trans);
 713                         break;
 714                 }
 715                 ret = btrfs_run_delayed_items_nr(trans, nr);
 716                 btrfs_end_transaction(trans);
 717                 break;
 718         case FLUSH_DELALLOC:
 719         case FLUSH_DELALLOC_WAIT:
 720                 shrink_delalloc(fs_info, space_info, num_bytes,
 721                                 state == FLUSH_DELALLOC_WAIT);
 722                 break;
 723         case FLUSH_DELAYED_REFS_NR:
 724         case FLUSH_DELAYED_REFS:
 725                 trans = btrfs_join_transaction(root);
 726                 if (IS_ERR(trans)) {
 727                         ret = PTR_ERR(trans);
 728                         break;
 729                 }
 730                 if (state == FLUSH_DELAYED_REFS_NR)
 731                         nr = calc_reclaim_items_nr(fs_info, num_bytes);
 732                 else
 733                         nr = 0;
 734                 btrfs_run_delayed_refs(trans, nr);
 735                 btrfs_end_transaction(trans);
 736                 break;
 737         case ALLOC_CHUNK:
 738         case ALLOC_CHUNK_FORCE:
 739                 trans = btrfs_join_transaction(root);
 740                 if (IS_ERR(trans)) {
 741                         ret = PTR_ERR(trans);
 742                         break;
 743                 }
 744                 ret = btrfs_chunk_alloc(trans,
 745                                 btrfs_get_alloc_profile(fs_info, space_info->flags),
 746                                 (state == ALLOC_CHUNK) ? CHUNK_ALLOC_NO_FORCE :
 747                                         CHUNK_ALLOC_FORCE);
 748                 btrfs_end_transaction(trans);
 749                 if (ret > 0 || ret == -ENOSPC)
 750                         ret = 0;
 751                 break;
 752         case RUN_DELAYED_IPUTS:
 753                 /*
 754                  * If we have pending delayed iputs then we could free up a
 755                  * bunch of pinned space, so make sure we run the iputs before
 756                  * we do our pinned bytes check below.
 757                  */
 758                 btrfs_run_delayed_iputs(fs_info);
 759                 btrfs_wait_on_delayed_iputs(fs_info);
 760                 break;
 761         case COMMIT_TRANS:
 762                 ret = may_commit_transaction(fs_info, space_info, num_bytes);
 763                 break;
 764         default:
 765                 ret = -ENOSPC;
 766                 break;
 767         }
 768
 769         trace_btrfs_flush_space(fs_info, space_info->flags, num_bytes, state,
 770                                 ret);
 771         return;
 772 }
 773
 774 static inline u64
 775 btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
 776                                  struct btrfs_space_info *space_info)
 777 {
 778         u64 used;
 779         u64 avail;
 780         u64 expected;
 781         u64 to_reclaim = space_info->reclaim_size;
 782
 783         lockdep_assert_held(&space_info->lock);
 784
 785         avail = calc_available_free_space(fs_info, space_info,
 786                                           BTRFS_RESERVE_FLUSH_ALL);
 787         used = btrfs_space_info_used(space_info, true);
 788
 789         /*
 790          * We may be flushing because suddenly we have less space than we had
 791          * before, and now we're well over-committed based on our current free
 792          * space.  If that's the case add in our overage so we make sure to put
 793          * appropriate pressure on the flushing state machine.
 794          */
 795         if (space_info->total_bytes + avail < used)
 796                 to_reclaim += used - (space_info->total_bytes + avail);
 797
 798         if (to_reclaim)
 799                 return to_reclaim;
 800
 801         to_reclaim = min_t(u64, num_online_cpus() * SZ_1M, SZ_16M);
 802         if (btrfs_can_overcommit(fs_info, space_info, to_reclaim,
 803                                  BTRFS_RESERVE_FLUSH_ALL))
 804                 return 0;
 805
 806         used = btrfs_space_info_used(space_info, true);
 807
 808         if (btrfs_can_overcommit(fs_info, space_info, SZ_1M,
 809                                  BTRFS_RESERVE_FLUSH_ALL))
 810                 expected = div_factor_fine(space_info->total_bytes, 95);
 811         else
 812                 expected = div_factor_fine(space_info->total_bytes, 90);
 813
 814         if (used > expected)
 815                 to_reclaim = used - expected;
 816         else
 817                 to_reclaim = 0;
 818         to_reclaim = min(to_reclaim, space_info->bytes_may_use +
 819                                      space_info->bytes_reserved);
 820         return to_reclaim;
 821 }
 822
 823 static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
 824                                         struct btrfs_space_info *space_info,
 825                                         u64 used)
 826 {
 827         u64 thresh = div_factor_fine(space_info->total_bytes, 98);
 828
 829         /* If we're just plain full then async reclaim just slows us down. */
 830         if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh)
 831                 return 0;
 832
 833         if (!btrfs_calc_reclaim_metadata_size(fs_info, space_info))
 834                 return 0;
 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         u64 first_ticket_bytes = 0;
 889
 890         if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
 891                 btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
 892                 __btrfs_dump_space_info(fs_info, space_info);
 893         }
 894
 895         while (!list_empty(&space_info->tickets) &&
 896                tickets_id == space_info->tickets_id) {
 897                 ticket = list_first_entry(&space_info->tickets,
 898                                           struct reserve_ticket, list);
 899
 900                 if (ticket->steal &&
 901                     steal_from_global_rsv(fs_info, space_info, ticket))
 902                         return true;
 903
 904                 /*
 905                  * may_commit_transaction will avoid committing the transaction
 906                  * if it doesn't feel like the space reclaimed by the commit
 907                  * would result in the ticket succeeding.  However if we have a
 908                  * smaller ticket in the queue it may be small enough to be
 909                  * satisified by committing the transaction, so if any
 910                  * subsequent ticket is smaller than the first ticket go ahead
 911                  * and send us back for another loop through the enospc flushing
 912                  * code.
 913                  */
 914                 if (first_ticket_bytes == 0)
 915                         first_ticket_bytes = ticket->bytes;
 916                 else if (first_ticket_bytes > ticket->bytes)
 917                         return true;
 918
 919                 if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
 920                         btrfs_info(fs_info, "failing ticket with %llu bytes",
 921                                    ticket->bytes);
 922
 923                 remove_ticket(space_info, ticket);
 924                 ticket->error = -ENOSPC;
 925                 wake_up(&ticket->wait);
 926
 927                 /*
 928                  * We're just throwing tickets away, so more flushing may not
 929                  * trip over btrfs_try_granting_tickets, so we need to call it
 930                  * here to see if we can make progress with the next ticket in
 931                  * the list.
 932                  */
 933                 btrfs_try_granting_tickets(fs_info, space_info);
 934         }
 935         return (tickets_id != space_info->tickets_id);
 936 }
 937
 938 /*
 939  * This is for normal flushers, we can wait all goddamned day if we want to.  We
 940  * will loop and continuously try to flush as long as we are making progress.
 941  * We count progress as clearing off tickets each time we have to loop.
 942  */
 943 static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 944 {
 945         struct btrfs_fs_info *fs_info;
 946         struct btrfs_space_info *space_info;
 947         u64 to_reclaim;
 948         int flush_state;
 949         int commit_cycles = 0;
 950         u64 last_tickets_id;
 951
 952         fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
 953         space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 954
 955         spin_lock(&space_info->lock);
 956         to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
 957         if (!to_reclaim) {
 958                 space_info->flush = 0;
 959                 spin_unlock(&space_info->lock);
 960                 return;
 961         }
 962         last_tickets_id = space_info->tickets_id;
 963         spin_unlock(&space_info->lock);
 964
 965         flush_state = FLUSH_DELAYED_ITEMS_NR;
 966         do {
 967                 flush_space(fs_info, space_info, to_reclaim, flush_state);
 968                 spin_lock(&space_info->lock);
 969                 if (list_empty(&space_info->tickets)) {
 970                         space_info->flush = 0;
 971                         spin_unlock(&space_info->lock);
 972                         return;
 973                 }
 974                 to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
 975                                                               space_info);
 976                 if (last_tickets_id == space_info->tickets_id) {
 977                         flush_state++;
 978                 } else {
 979                         last_tickets_id = space_info->tickets_id;
 980                         flush_state = FLUSH_DELAYED_ITEMS_NR;
 981                         if (commit_cycles)
 982                                 commit_cycles--;
 983                 }
 984
 985                 /*
 986                  * We don't want to force a chunk allocation until we've tried
 987                  * pretty hard to reclaim space.  Think of the case where we
 988                  * freed up a bunch of space and so have a lot of pinned space
 989                  * to reclaim.  We would rather use that than possibly create a
 990                  * underutilized metadata chunk.  So if this is our first run
 991                  * through the flushing state machine skip ALLOC_CHUNK_FORCE and
 992                  * commit the transaction.  If nothing has changed the next go
 993                  * around then we can force a chunk allocation.
 994                  */
 995                 if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
 996                         flush_state++;
 997
 998                 if (flush_state > COMMIT_TRANS) {
 999                         commit_cycles++;
1000                         if (commit_cycles > 2) {
1001                                 if (maybe_fail_all_tickets(fs_info, space_info)) {
1002                                         flush_state = FLUSH_DELAYED_ITEMS_NR;
1003                                         commit_cycles--;
1004                                 } else {
1005                                         space_info->flush = 0;
1006                                 }
1007                         } else {
1008                                 flush_state = FLUSH_DELAYED_ITEMS_NR;
1009                         }
1010                 }
1011                 spin_unlock(&space_info->lock);
1012         } while (flush_state <= COMMIT_TRANS);
1013 }
1014
1015 void btrfs_init_async_reclaim_work(struct work_struct *work)
1016 {
1017         INIT_WORK(work, btrfs_async_reclaim_metadata_space);
1018 }
1019
1020 static const enum btrfs_flush_state priority_flush_states[] = {
1021         FLUSH_DELAYED_ITEMS_NR,
1022         FLUSH_DELAYED_ITEMS,
1023         ALLOC_CHUNK,
1024 };
1025
1026 static const enum btrfs_flush_state evict_flush_states[] = {
1027         FLUSH_DELAYED_ITEMS_NR,
1028         FLUSH_DELAYED_ITEMS,
1029         FLUSH_DELAYED_REFS_NR,
1030         FLUSH_DELAYED_REFS,
1031         FLUSH_DELALLOC,
1032         FLUSH_DELALLOC_WAIT,
1033         ALLOC_CHUNK,
1034         COMMIT_TRANS,
1035 };
1036
1037 static const enum btrfs_flush_state data_flush_states[] = {
1038         FLUSH_DELALLOC_WAIT,
1039         COMMIT_TRANS,
1040         RUN_DELAYED_IPUTS,
1041 };
1042
1043 static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
1044                                 struct btrfs_space_info *space_info,
1045                                 struct reserve_ticket *ticket,
1046                                 const enum btrfs_flush_state *states,
1047                                 int states_nr)
1048 {
1049         u64 to_reclaim;
1050         int flush_state;
1051
1052         spin_lock(&space_info->lock);
1053         to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
1054         if (!to_reclaim) {
1055                 spin_unlock(&space_info->lock);
1056                 return;
1057         }
1058         spin_unlock(&space_info->lock);
1059
1060         flush_state = 0;
1061         do {
1062                 flush_space(fs_info, space_info, to_reclaim, states[flush_state]);
1063                 flush_state++;
1064                 spin_lock(&space_info->lock);
1065                 if (ticket->bytes == 0) {
1066                         spin_unlock(&space_info->lock);
1067                         return;
1068                 }
1069                 spin_unlock(&space_info->lock);
1070         } while (flush_state < states_nr);
1071 }
1072
1073 static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
1074                                 struct btrfs_space_info *space_info,
1075                                 struct reserve_ticket *ticket)
1076
1077 {
1078         DEFINE_WAIT(wait);
1079         int ret = 0;
1080
1081         spin_lock(&space_info->lock);
1082         while (ticket->bytes > 0 && ticket->error == 0) {
1083                 ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
1084                 if (ret) {
1085                         /*
1086                          * Delete us from the list. After we unlock the space
1087                          * info, we don't want the async reclaim job to reserve
1088                          * space for this ticket. If that would happen, then the
1089                          * ticket's task would not known that space was reserved
1090                          * despite getting an error, resulting in a space leak
1091                          * (bytes_may_use counter of our space_info).
1092                          */
1093                         remove_ticket(space_info, ticket);
1094                         ticket->error = -EINTR;
1095                         break;
1096                 }
1097                 spin_unlock(&space_info->lock);
1098
1099                 schedule();
1100
1101                 finish_wait(&ticket->wait, &wait);
1102                 spin_lock(&space_info->lock);
1103         }
1104         spin_unlock(&space_info->lock);
1105 }
1106
1107 /**
1108  * handle_reserve_ticket - do the appropriate flushing and waiting for a ticket
1109  * @fs_info - the fs
1110  * @space_info - the space_info for the reservation
1111  * @ticket - the ticket for the reservation
1112  * @flush - how much we can flush
1113  *
1114  * This does the work of figuring out how to flush for the ticket, waiting for
1115  * the reservation, and returning the appropriate error if there is one.
1116  */
1117 static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
1118                                  struct btrfs_space_info *space_info,
1119                                  struct reserve_ticket *ticket,
1120                                  enum btrfs_reserve_flush_enum flush)
1121 {
1122         int ret;
1123
1124         switch (flush) {
1125         case BTRFS_RESERVE_FLUSH_ALL:
1126         case BTRFS_RESERVE_FLUSH_ALL_STEAL:
1127                 wait_reserve_ticket(fs_info, space_info, ticket);
1128                 break;
1129         case BTRFS_RESERVE_FLUSH_LIMIT:
1130                 priority_reclaim_metadata_space(fs_info, space_info, ticket,
1131                                                 priority_flush_states,
1132                                                 ARRAY_SIZE(priority_flush_states));
1133                 break;
1134         case BTRFS_RESERVE_FLUSH_EVICT:
1135                 priority_reclaim_metadata_space(fs_info, space_info, ticket,
1136                                                 evict_flush_states,
1137                                                 ARRAY_SIZE(evict_flush_states));
1138                 break;
1139         default:
1140                 ASSERT(0);
1141                 break;
1142         }
1143
1144         spin_lock(&space_info->lock);
1145         ret = ticket->error;
1146         if (ticket->bytes || ticket->error) {
1147                 /*
1148                  * We were a priority ticket, so we need to delete ourselves
1149                  * from the list.  Because we could have other priority tickets
1150                  * behind us that require less space, run
1151                  * btrfs_try_granting_tickets() to see if their reservations can
1152                  * now be made.
1153                  */
1154                 if (!list_empty(&ticket->list)) {
1155                         remove_ticket(space_info, ticket);
1156                         btrfs_try_granting_tickets(fs_info, space_info);
1157                 }
1158
1159                 if (!ret)
1160                         ret = -ENOSPC;
1161         }
1162         spin_unlock(&space_info->lock);
1163         ASSERT(list_empty(&ticket->list));
1164         /*
1165          * Check that we can't have an error set if the reservation succeeded,
1166          * as that would confuse tasks and lead them to error out without
1167          * releasing reserved space (if an error happens the expectation is that
1168          * space wasn't reserved at all).
1169          */
1170         ASSERT(!(ticket->bytes == 0 && ticket->error));
1171         return ret;
1172 }
1173
1174 /*
1175  * This returns true if this flush state will go through the ordinary flushing
1176  * code.
1177  */
1178 static inline bool is_normal_flushing(enum btrfs_reserve_flush_enum flush)
1179 {
1180         return  (flush == BTRFS_RESERVE_FLUSH_ALL) ||
1181                 (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
1182 }
1183
1184 /**
1185  * reserve_metadata_bytes - try to reserve bytes from the block_rsv's space
1186  * @root - the root we're allocating for
1187  * @space_info - the space info we want to allocate from
1188  * @orig_bytes - the number of bytes we want
1189  * @flush - whether or not we can flush to make our reservation
1190  *
1191  * This will reserve orig_bytes number of bytes from the space info associated
1192  * with the block_rsv.  If there is not enough space it will make an attempt to
1193  * flush out space to make room.  It will do this by flushing delalloc if
1194  * possible or committing the transaction.  If flush is 0 then no attempts to
1195  * regain reservations will be made and this will fail if there is not enough
1196  * space already.
1197  */
1198 static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
1199                                     struct btrfs_space_info *space_info,
1200                                     u64 orig_bytes,
1201                                     enum btrfs_reserve_flush_enum flush)
1202 {
1203         struct reserve_ticket ticket;
1204         u64 used;
1205         int ret = 0;
1206         bool pending_tickets;
1207
1208         ASSERT(orig_bytes);
1209         ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
1210
1211         spin_lock(&space_info->lock);
1212         ret = -ENOSPC;
1213         used = btrfs_space_info_used(space_info, true);
1214
1215         /*
1216          * We don't want NO_FLUSH allocations to jump everybody, they can
1217          * generally handle ENOSPC in a different way, so treat them the same as
1218          * normal flushers when it comes to skipping pending tickets.
1219          */
1220         if (is_normal_flushing(flush) || (flush == BTRFS_RESERVE_NO_FLUSH))
1221                 pending_tickets = !list_empty(&space_info->tickets) ||
1222                         !list_empty(&space_info->priority_tickets);
1223         else
1224                 pending_tickets = !list_empty(&space_info->priority_tickets);
1225
1226         /*
1227          * Carry on if we have enough space (short-circuit) OR call
1228          * can_overcommit() to ensure we can overcommit to continue.
1229          */
1230         if (!pending_tickets &&
1231             ((used + orig_bytes <= space_info->total_bytes) ||
1232              btrfs_can_overcommit(fs_info, space_info, orig_bytes, flush))) {
1233                 btrfs_space_info_update_bytes_may_use(fs_info, space_info,
1234                                                       orig_bytes);
1235                 ret = 0;
1236         }
1237
1238         /*
1239          * If we couldn't make a reservation then setup our reservation ticket
1240          * and kick the async worker if it's not already running.
1241          *
1242          * If we are a priority flusher then we just need to add our ticket to
1243          * the list and we will do our own flushing further down.
1244          */
1245         if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
1246                 ticket.bytes = orig_bytes;
1247                 ticket.error = 0;
1248                 space_info->reclaim_size += ticket.bytes;
1249                 init_waitqueue_head(&ticket.wait);
1250                 ticket.steal = (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
1251                 if (flush == BTRFS_RESERVE_FLUSH_ALL ||
1252                     flush == BTRFS_RESERVE_FLUSH_ALL_STEAL) {
1253                         list_add_tail(&ticket.list, &space_info->tickets);
1254                         if (!space_info->flush) {
1255                                 space_info->flush = 1;
1256                                 trace_btrfs_trigger_flush(fs_info,
1257                                                           space_info->flags,
1258                                                           orig_bytes, flush,
1259                                                           "enospc");
1260                                 queue_work(system_unbound_wq,
1261                                            &fs_info->async_reclaim_work);
1262                         }
1263                 } else {
1264                         list_add_tail(&ticket.list,
1265                                       &space_info->priority_tickets);
1266                 }
1267         } else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
1268                 used += orig_bytes;
1269                 /*
1270                  * We will do the space reservation dance during log replay,
1271                  * which means we won't have fs_info->fs_root set, so don't do
1272                  * the async reclaim as we will panic.
1273                  */
1274                 if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
1275                     need_do_async_reclaim(fs_info, space_info, used) &&
1276                     !work_busy(&fs_info->async_reclaim_work)) {
1277                         trace_btrfs_trigger_flush(fs_info, space_info->flags,
1278                                                   orig_bytes, flush, "preempt");
1279                         queue_work(system_unbound_wq,
1280                                    &fs_info->async_reclaim_work);
1281                 }
1282         }
1283         spin_unlock(&space_info->lock);
1284         if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
1285                 return ret;
1286
1287         return handle_reserve_ticket(fs_info, space_info, &ticket, flush);
1288 }
1289
1290 /**
1291  * reserve_metadata_bytes - try to reserve bytes from the block_rsv's space
1292  * @root - the root we're allocating for
1293  * @block_rsv - the block_rsv we're allocating for
1294  * @orig_bytes - the number of bytes we want
1295  * @flush - whether or not we can flush to make our reservation
1296  *
1297  * This will reserve orig_bytes number of bytes from the space info associated
1298  * with the block_rsv.  If there is not enough space it will make an attempt to
1299  * flush out space to make room.  It will do this by flushing delalloc if
1300  * possible or committing the transaction.  If flush is 0 then no attempts to
1301  * regain reservations will be made and this will fail if there is not enough
1302  * space already.
1303  */
1304 int btrfs_reserve_metadata_bytes(struct btrfs_root *root,
1305                                  struct btrfs_block_rsv *block_rsv,
1306                                  u64 orig_bytes,
1307                                  enum btrfs_reserve_flush_enum flush)
1308 {
1309         struct btrfs_fs_info *fs_info = root->fs_info;
1310         struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
1311         int ret;
1312
1313         ret = __reserve_metadata_bytes(fs_info, block_rsv->space_info,
1314                                        orig_bytes, flush);
1315         if (ret == -ENOSPC &&
1316             unlikely(root->orphan_cleanup_state == ORPHAN_CLEANUP_STARTED)) {
1317                 if (block_rsv != global_rsv &&
1318                     !btrfs_block_rsv_use_bytes(global_rsv, orig_bytes))
1319                         ret = 0;
1320         }
1321         if (ret == -ENOSPC) {
1322                 trace_btrfs_space_reservation(fs_info, "space_info:enospc",
1323                                               block_rsv->space_info->flags,
1324                                               orig_bytes, 1);
1325
1326                 if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
1327                         btrfs_dump_space_info(fs_info, block_rsv->space_info,
1328                                               orig_bytes, 0);
1329         }
1330         return ret;
1331 }