linux/fs/btrfs/space-info.c
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   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
 161u64 __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 */
 175void 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
 184static 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
 217int 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        }
 250out:
 251        return ret;
 252}
 253
 254void 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
 280struct 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
 295static 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
 331int 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
 350static 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 */
 364void 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;
 373again:
 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)                               \
 404do {                                                                    \
 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
 412static 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
 436void 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);
 451again:
 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
 467static 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 */
 485static 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);
 578skip_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 */
 616static 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->tree_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
 706static inline u64
 707btrfs_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
 732static 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
 840static 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 (!ticket->steal)
 848                return false;
 849
 850        if (global_rsv->space_info != space_info)
 851                return false;
 852
 853        spin_lock(&global_rsv->lock);
 854        min_bytes = div_factor(global_rsv->size, 1);
 855        if (global_rsv->reserved < min_bytes + ticket->bytes) {
 856                spin_unlock(&global_rsv->lock);
 857                return false;
 858        }
 859        global_rsv->reserved -= ticket->bytes;
 860        remove_ticket(space_info, ticket);
 861        ticket->bytes = 0;
 862        wake_up(&ticket->wait);
 863        space_info->tickets_id++;
 864        if (global_rsv->reserved < global_rsv->size)
 865                global_rsv->full = 0;
 866        spin_unlock(&global_rsv->lock);
 867
 868        return true;
 869}
 870
 871/*
 872 * maybe_fail_all_tickets - we've exhausted our flushing, start failing tickets
 873 * @fs_info - fs_info for this fs
 874 * @space_info - the space info we were flushing
 875 *
 876 * We call this when we've exhausted our flushing ability and haven't made
 877 * progress in satisfying tickets.  The reservation code handles tickets in
 878 * order, so if there is a large ticket first and then smaller ones we could
 879 * very well satisfy the smaller tickets.  This will attempt to wake up any
 880 * tickets in the list to catch this case.
 881 *
 882 * This function returns true if it was able to make progress by clearing out
 883 * other tickets, or if it stumbles across a ticket that was smaller than the
 884 * first ticket.
 885 */
 886static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
 887                                   struct btrfs_space_info *space_info)
 888{
 889        struct reserve_ticket *ticket;
 890        u64 tickets_id = space_info->tickets_id;
 891        const bool aborted = BTRFS_FS_ERROR(fs_info);
 892
 893        trace_btrfs_fail_all_tickets(fs_info, space_info);
 894
 895        if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
 896                btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
 897                __btrfs_dump_space_info(fs_info, space_info);
 898        }
 899
 900        while (!list_empty(&space_info->tickets) &&
 901               tickets_id == space_info->tickets_id) {
 902                ticket = list_first_entry(&space_info->tickets,
 903                                          struct reserve_ticket, list);
 904
 905                if (!aborted && steal_from_global_rsv(fs_info, space_info, ticket))
 906                        return true;
 907
 908                if (!aborted && btrfs_test_opt(fs_info, ENOSPC_DEBUG))
 909                        btrfs_info(fs_info, "failing ticket with %llu bytes",
 910                                   ticket->bytes);
 911
 912                remove_ticket(space_info, ticket);
 913                if (aborted)
 914                        ticket->error = -EIO;
 915                else
 916                        ticket->error = -ENOSPC;
 917                wake_up(&ticket->wait);
 918
 919                /*
 920                 * We're just throwing tickets away, so more flushing may not
 921                 * trip over btrfs_try_granting_tickets, so we need to call it
 922                 * here to see if we can make progress with the next ticket in
 923                 * the list.
 924                 */
 925                if (!aborted)
 926                        btrfs_try_granting_tickets(fs_info, space_info);
 927        }
 928        return (tickets_id != space_info->tickets_id);
 929}
 930
 931/*
 932 * This is for normal flushers, we can wait all goddamned day if we want to.  We
 933 * will loop and continuously try to flush as long as we are making progress.
 934 * We count progress as clearing off tickets each time we have to loop.
 935 */
 936static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 937{
 938        struct btrfs_fs_info *fs_info;
 939        struct btrfs_space_info *space_info;
 940        u64 to_reclaim;
 941        enum btrfs_flush_state flush_state;
 942        int commit_cycles = 0;
 943        u64 last_tickets_id;
 944
 945        fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
 946        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 947
 948        spin_lock(&space_info->lock);
 949        to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
 950        if (!to_reclaim) {
 951                space_info->flush = 0;
 952                spin_unlock(&space_info->lock);
 953                return;
 954        }
 955        last_tickets_id = space_info->tickets_id;
 956        spin_unlock(&space_info->lock);
 957
 958        flush_state = FLUSH_DELAYED_ITEMS_NR;
 959        do {
 960                flush_space(fs_info, space_info, to_reclaim, flush_state, false);
 961                spin_lock(&space_info->lock);
 962                if (list_empty(&space_info->tickets)) {
 963                        space_info->flush = 0;
 964                        spin_unlock(&space_info->lock);
 965                        return;
 966                }
 967                to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
 968                                                              space_info);
 969                if (last_tickets_id == space_info->tickets_id) {
 970                        flush_state++;
 971                } else {
 972                        last_tickets_id = space_info->tickets_id;
 973                        flush_state = FLUSH_DELAYED_ITEMS_NR;
 974                        if (commit_cycles)
 975                                commit_cycles--;
 976                }
 977
 978                /*
 979                 * We do not want to empty the system of delalloc unless we're
 980                 * under heavy pressure, so allow one trip through the flushing
 981                 * logic before we start doing a FLUSH_DELALLOC_FULL.
 982                 */
 983                if (flush_state == FLUSH_DELALLOC_FULL && !commit_cycles)
 984                        flush_state++;
 985
 986                /*
 987                 * We don't want to force a chunk allocation until we've tried
 988                 * pretty hard to reclaim space.  Think of the case where we
 989                 * freed up a bunch of space and so have a lot of pinned space
 990                 * to reclaim.  We would rather use that than possibly create a
 991                 * underutilized metadata chunk.  So if this is our first run
 992                 * through the flushing state machine skip ALLOC_CHUNK_FORCE and
 993                 * commit the transaction.  If nothing has changed the next go
 994                 * around then we can force a chunk allocation.
 995                 */
 996                if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
 997                        flush_state++;
 998
 999                if (flush_state > COMMIT_TRANS) {
1000                        commit_cycles++;
1001                        if (commit_cycles > 2) {
1002                                if (maybe_fail_all_tickets(fs_info, space_info)) {
1003                                        flush_state = FLUSH_DELAYED_ITEMS_NR;
1004                                        commit_cycles--;
1005                                } else {
1006                                        space_info->flush = 0;
1007                                }
1008                        } else {
1009                                flush_state = FLUSH_DELAYED_ITEMS_NR;
1010                        }
1011                }
1012                spin_unlock(&space_info->lock);
1013        } while (flush_state <= COMMIT_TRANS);
1014}
1015
1016/*
1017 * This handles pre-flushing of metadata space before we get to the point that
1018 * we need to start blocking threads on tickets.  The logic here is different
1019 * from the other flush paths because it doesn't rely on tickets to tell us how
1020 * much we need to flush, instead it attempts to keep us below the 80% full
1021 * watermark of space by flushing whichever reservation pool is currently the
1022 * largest.
1023 */
1024static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
1025{
1026        struct btrfs_fs_info *fs_info;
1027        struct btrfs_space_info *space_info;
1028        struct btrfs_block_rsv *delayed_block_rsv;
1029        struct btrfs_block_rsv *delayed_refs_rsv;
1030        struct btrfs_block_rsv *global_rsv;
1031        struct btrfs_block_rsv *trans_rsv;
1032        int loops = 0;
1033
1034        fs_info = container_of(work, struct btrfs_fs_info,
1035                               preempt_reclaim_work);
1036        space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
1037        delayed_block_rsv = &fs_info->delayed_block_rsv;
1038        delayed_refs_rsv = &fs_info->delayed_refs_rsv;
1039        global_rsv = &fs_info->global_block_rsv;
1040        trans_rsv = &fs_info->trans_block_rsv;
1041
1042        spin_lock(&space_info->lock);
1043        while (need_preemptive_reclaim(fs_info, space_info)) {
1044                enum btrfs_flush_state flush;
1045                u64 delalloc_size = 0;
1046                u64 to_reclaim, block_rsv_size;
1047                u64 global_rsv_size = global_rsv->reserved;
1048
1049                loops++;
1050
1051                /*
1052                 * We don't have a precise counter for the metadata being
1053                 * reserved for delalloc, so we'll approximate it by subtracting
1054                 * out the block rsv's space from the bytes_may_use.  If that
1055                 * amount is higher than the individual reserves, then we can
1056                 * assume it's tied up in delalloc reservations.
1057                 */
1058                block_rsv_size = global_rsv_size +
1059                        delayed_block_rsv->reserved +
1060                        delayed_refs_rsv->reserved +
1061                        trans_rsv->reserved;
1062                if (block_rsv_size < space_info->bytes_may_use)
1063                        delalloc_size = space_info->bytes_may_use - block_rsv_size;
1064                spin_unlock(&space_info->lock);
1065
1066                /*
1067                 * We don't want to include the global_rsv in our calculation,
1068                 * because that's space we can't touch.  Subtract it from the
1069                 * block_rsv_size for the next checks.
1070                 */
1071                block_rsv_size -= global_rsv_size;
1072
1073                /*
1074                 * We really want to avoid flushing delalloc too much, as it
1075                 * could result in poor allocation patterns, so only flush it if
1076                 * it's larger than the rest of the pools combined.
1077                 */
1078                if (delalloc_size > block_rsv_size) {
1079                        to_reclaim = delalloc_size;
1080                        flush = FLUSH_DELALLOC;
1081                } else if (space_info->bytes_pinned >
1082                           (delayed_block_rsv->reserved +
1083                            delayed_refs_rsv->reserved)) {
1084                        to_reclaim = space_info->bytes_pinned;
1085                        flush = COMMIT_TRANS;
1086                } else if (delayed_block_rsv->reserved >
1087                           delayed_refs_rsv->reserved) {
1088                        to_reclaim = delayed_block_rsv->reserved;
1089                        flush = FLUSH_DELAYED_ITEMS_NR;
1090                } else {
1091                        to_reclaim = delayed_refs_rsv->reserved;
1092                        flush = FLUSH_DELAYED_REFS_NR;
1093                }
1094
1095                /*
1096                 * We don't want to reclaim everything, just a portion, so scale
1097                 * down the to_reclaim by 1/4.  If it takes us down to 0,
1098                 * reclaim 1 items worth.
1099                 */
1100                to_reclaim >>= 2;
1101                if (!to_reclaim)
1102                        to_reclaim = btrfs_calc_insert_metadata_size(fs_info, 1);
1103                flush_space(fs_info, space_info, to_reclaim, flush, true);
1104                cond_resched();
1105                spin_lock(&space_info->lock);
1106        }
1107
1108        /* We only went through once, back off our clamping. */
1109        if (loops == 1 && !space_info->reclaim_size)
1110                space_info->clamp = max(1, space_info->clamp - 1);
1111        trace_btrfs_done_preemptive_reclaim(fs_info, space_info);
1112        spin_unlock(&space_info->lock);
1113}
1114
1115/*
1116 * FLUSH_DELALLOC_WAIT:
1117 *   Space is freed from flushing delalloc in one of two ways.
1118 *
1119 *   1) compression is on and we allocate less space than we reserved
1120 *   2) we are overwriting existing space
1121 *
1122 *   For #1 that extra space is reclaimed as soon as the delalloc pages are
1123 *   COWed, by way of btrfs_add_reserved_bytes() which adds the actual extent
1124 *   length to ->bytes_reserved, and subtracts the reserved space from
1125 *   ->bytes_may_use.
1126 *
1127 *   For #2 this is trickier.  Once the ordered extent runs we will drop the
1128 *   extent in the range we are overwriting, which creates a delayed ref for
1129 *   that freed extent.  This however is not reclaimed until the transaction
1130 *   commits, thus the next stages.
1131 *
1132 * RUN_DELAYED_IPUTS
1133 *   If we are freeing inodes, we want to make sure all delayed iputs have
1134 *   completed, because they could have been on an inode with i_nlink == 0, and
1135 *   thus have been truncated and freed up space.  But again this space is not
1136 *   immediately re-usable, it comes in the form of a delayed ref, which must be
1137 *   run and then the transaction must be committed.
1138 *
1139 * COMMIT_TRANS
1140 *   This is where we reclaim all of the pinned space generated by running the
1141 *   iputs
1142 *
1143 * ALLOC_CHUNK_FORCE
1144 *   For data we start with alloc chunk force, however we could have been full
1145 *   before, and then the transaction commit could have freed new block groups,
1146 *   so if we now have space to allocate do the force chunk allocation.
1147 */
1148static const enum btrfs_flush_state data_flush_states[] = {
1149        FLUSH_DELALLOC_FULL,
1150        RUN_DELAYED_IPUTS,
1151        COMMIT_TRANS,
1152        ALLOC_CHUNK_FORCE,
1153};
1154
1155static void btrfs_async_reclaim_data_space(struct work_struct *work)
1156{
1157        struct btrfs_fs_info *fs_info;
1158        struct btrfs_space_info *space_info;
1159        u64 last_tickets_id;
1160        enum btrfs_flush_state flush_state = 0;
1161
1162        fs_info = container_of(work, struct btrfs_fs_info, async_data_reclaim_work);
1163        space_info = fs_info->data_sinfo;
1164
1165        spin_lock(&space_info->lock);
1166        if (list_empty(&space_info->tickets)) {
1167                space_info->flush = 0;
1168                spin_unlock(&space_info->lock);
1169                return;
1170        }
1171        last_tickets_id = space_info->tickets_id;
1172        spin_unlock(&space_info->lock);
1173
1174        while (!space_info->full) {
1175                flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
1176                spin_lock(&space_info->lock);
1177                if (list_empty(&space_info->tickets)) {
1178                        space_info->flush = 0;
1179                        spin_unlock(&space_info->lock);
1180                        return;
1181                }
1182
1183                /* Something happened, fail everything and bail. */
1184                if (BTRFS_FS_ERROR(fs_info))
1185                        goto aborted_fs;
1186                last_tickets_id = space_info->tickets_id;
1187                spin_unlock(&space_info->lock);
1188        }
1189
1190        while (flush_state < ARRAY_SIZE(data_flush_states)) {
1191                flush_space(fs_info, space_info, U64_MAX,
1192                            data_flush_states[flush_state], false);
1193                spin_lock(&space_info->lock);
1194                if (list_empty(&space_info->tickets)) {
1195                        space_info->flush = 0;
1196                        spin_unlock(&space_info->lock);
1197                        return;
1198                }
1199
1200                if (last_tickets_id == space_info->tickets_id) {
1201                        flush_state++;
1202                } else {
1203                        last_tickets_id = space_info->tickets_id;
1204                        flush_state = 0;
1205                }
1206
1207                if (flush_state >= ARRAY_SIZE(data_flush_states)) {
1208                        if (space_info->full) {
1209                                if (maybe_fail_all_tickets(fs_info, space_info))
1210                                        flush_state = 0;
1211                                else
1212                                        space_info->flush = 0;
1213                        } else {
1214                                flush_state = 0;
1215                        }
1216
1217                        /* Something happened, fail everything and bail. */
1218                        if (BTRFS_FS_ERROR(fs_info))
1219                                goto aborted_fs;
1220
1221                }
1222                spin_unlock(&space_info->lock);
1223        }
1224        return;
1225
1226aborted_fs:
1227        maybe_fail_all_tickets(fs_info, space_info);
1228        space_info->flush = 0;
1229        spin_unlock(&space_info->lock);
1230}
1231
1232void btrfs_init_async_reclaim_work(struct btrfs_fs_info *fs_info)
1233{
1234        INIT_WORK(&fs_info->async_reclaim_work, btrfs_async_reclaim_metadata_space);
1235        INIT_WORK(&fs_info->async_data_reclaim_work, btrfs_async_reclaim_data_space);
1236        INIT_WORK(&fs_info->preempt_reclaim_work,
1237                  btrfs_preempt_reclaim_metadata_space);
1238}
1239
1240static const enum btrfs_flush_state priority_flush_states[] = {
1241        FLUSH_DELAYED_ITEMS_NR,
1242        FLUSH_DELAYED_ITEMS,
1243        ALLOC_CHUNK,
1244};
1245
1246static const enum btrfs_flush_state evict_flush_states[] = {
1247        FLUSH_DELAYED_ITEMS_NR,
1248        FLUSH_DELAYED_ITEMS,
1249        FLUSH_DELAYED_REFS_NR,
1250        FLUSH_DELAYED_REFS,
1251        FLUSH_DELALLOC,
1252        FLUSH_DELALLOC_WAIT,
1253        FLUSH_DELALLOC_FULL,
1254        ALLOC_CHUNK,
1255        COMMIT_TRANS,
1256};
1257
1258static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
1259                                struct btrfs_space_info *space_info,
1260                                struct reserve_ticket *ticket,
1261                                const enum btrfs_flush_state *states,
1262                                int states_nr)
1263{
1264        u64 to_reclaim;
1265        int flush_state = 0;
1266
1267        spin_lock(&space_info->lock);
1268        to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
1269        /*
1270         * This is the priority reclaim path, so to_reclaim could be >0 still
1271         * because we may have only satisified the priority tickets and still
1272         * left non priority tickets on the list.  We would then have
1273         * to_reclaim but ->bytes == 0.
1274         */
1275        if (ticket->bytes == 0) {
1276                spin_unlock(&space_info->lock);
1277                return;
1278        }
1279
1280        while (flush_state < states_nr) {
1281                spin_unlock(&space_info->lock);
1282                flush_space(fs_info, space_info, to_reclaim, states[flush_state],
1283                            false);
1284                flush_state++;
1285                spin_lock(&space_info->lock);
1286                if (ticket->bytes == 0) {
1287                        spin_unlock(&space_info->lock);
1288                        return;
1289                }
1290        }
1291
1292        /* Attempt to steal from the global rsv if we can. */
1293        if (!steal_from_global_rsv(fs_info, space_info, ticket)) {
1294                ticket->error = -ENOSPC;
1295                remove_ticket(space_info, ticket);
1296        }
1297
1298        /*
1299         * We must run try_granting_tickets here because we could be a large
1300         * ticket in front of a smaller ticket that can now be satisfied with
1301         * the available space.
1302         */
1303        btrfs_try_granting_tickets(fs_info, space_info);
1304        spin_unlock(&space_info->lock);
1305}
1306
1307static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
1308                                        struct btrfs_space_info *space_info,
1309                                        struct reserve_ticket *ticket)
1310{
1311        spin_lock(&space_info->lock);
1312
1313        /* We could have been granted before we got here. */
1314        if (ticket->bytes == 0) {
1315                spin_unlock(&space_info->lock);
1316                return;
1317        }
1318
1319        while (!space_info->full) {
1320                spin_unlock(&space_info->lock);
1321                flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
1322                spin_lock(&space_info->lock);
1323                if (ticket->bytes == 0) {
1324                        spin_unlock(&space_info->lock);
1325                        return;
1326                }
1327        }
1328
1329        ticket->error = -ENOSPC;
1330        remove_ticket(space_info, ticket);
1331        btrfs_try_granting_tickets(fs_info, space_info);
1332        spin_unlock(&space_info->lock);
1333}
1334
1335static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
1336                                struct btrfs_space_info *space_info,
1337                                struct reserve_ticket *ticket)
1338
1339{
1340        DEFINE_WAIT(wait);
1341        int ret = 0;
1342
1343        spin_lock(&space_info->lock);
1344        while (ticket->bytes > 0 && ticket->error == 0) {
1345                ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
1346                if (ret) {
1347                        /*
1348                         * Delete us from the list. After we unlock the space
1349                         * info, we don't want the async reclaim job to reserve
1350                         * space for this ticket. If that would happen, then the
1351                         * ticket's task would not known that space was reserved
1352                         * despite getting an error, resulting in a space leak
1353                         * (bytes_may_use counter of our space_info).
1354                         */
1355                        remove_ticket(space_info, ticket);
1356                        ticket->error = -EINTR;
1357                        break;
1358                }
1359                spin_unlock(&space_info->lock);
1360
1361                schedule();
1362
1363                finish_wait(&ticket->wait, &wait);
1364                spin_lock(&space_info->lock);
1365        }
1366        spin_unlock(&space_info->lock);
1367}
1368
1369/**
1370 * Do the appropriate flushing and waiting for a ticket
1371 *
1372 * @fs_info:    the filesystem
1373 * @space_info: space info for the reservation
1374 * @ticket:     ticket for the reservation
1375 * @start_ns:   timestamp when the reservation started
1376 * @orig_bytes: amount of bytes originally reserved
1377 * @flush:      how much we can flush
1378 *
1379 * This does the work of figuring out how to flush for the ticket, waiting for
1380 * the reservation, and returning the appropriate error if there is one.
1381 */
1382static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
1383                                 struct btrfs_space_info *space_info,
1384                                 struct reserve_ticket *ticket,
1385                                 u64 start_ns, u64 orig_bytes,
1386                                 enum btrfs_reserve_flush_enum flush)
1387{
1388        int ret;
1389
1390        switch (flush) {
1391        case BTRFS_RESERVE_FLUSH_DATA:
1392        case BTRFS_RESERVE_FLUSH_ALL:
1393        case BTRFS_RESERVE_FLUSH_ALL_STEAL:
1394                wait_reserve_ticket(fs_info, space_info, ticket);
1395                break;
1396        case BTRFS_RESERVE_FLUSH_LIMIT:
1397                priority_reclaim_metadata_space(fs_info, space_info, ticket,
1398                                                priority_flush_states,
1399                                                ARRAY_SIZE(priority_flush_states));
1400                break;
1401        case BTRFS_RESERVE_FLUSH_EVICT:
1402                priority_reclaim_metadata_space(fs_info, space_info, ticket,
1403                                                evict_flush_states,
1404                                                ARRAY_SIZE(evict_flush_states));
1405                break;
1406        case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
1407                priority_reclaim_data_space(fs_info, space_info, ticket);
1408                break;
1409        default:
1410                ASSERT(0);
1411                break;
1412        }
1413
1414        ret = ticket->error;
1415        ASSERT(list_empty(&ticket->list));
1416        /*
1417         * Check that we can't have an error set if the reservation succeeded,
1418         * as that would confuse tasks and lead them to error out without
1419         * releasing reserved space (if an error happens the expectation is that
1420         * space wasn't reserved at all).
1421         */
1422        ASSERT(!(ticket->bytes == 0 && ticket->error));
1423        trace_btrfs_reserve_ticket(fs_info, space_info->flags, orig_bytes,
1424                                   start_ns, flush, ticket->error);
1425        return ret;
1426}
1427
1428/*
1429 * This returns true if this flush state will go through the ordinary flushing
1430 * code.
1431 */
1432static inline bool is_normal_flushing(enum btrfs_reserve_flush_enum flush)
1433{
1434        return  (flush == BTRFS_RESERVE_FLUSH_ALL) ||
1435                (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
1436}
1437
1438static inline void maybe_clamp_preempt(struct btrfs_fs_info *fs_info,
1439                                       struct btrfs_space_info *space_info)
1440{
1441        u64 ordered = percpu_counter_sum_positive(&fs_info->ordered_bytes);
1442        u64 delalloc = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
1443
1444        /*
1445         * If we're heavy on ordered operations then clamping won't help us.  We
1446         * need to clamp specifically to keep up with dirty'ing buffered
1447         * writers, because there's not a 1:1 correlation of writing delalloc
1448         * and freeing space, like there is with flushing delayed refs or
1449         * delayed nodes.  If we're already more ordered than delalloc then
1450         * we're keeping up, otherwise we aren't and should probably clamp.
1451         */
1452        if (ordered < delalloc)
1453                space_info->clamp = min(space_info->clamp + 1, 8);
1454}
1455
1456static inline bool can_steal(enum btrfs_reserve_flush_enum flush)
1457{
1458        return (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
1459                flush == BTRFS_RESERVE_FLUSH_EVICT);
1460}
1461
1462/**
1463 * Try to reserve bytes from the block_rsv's space
1464 *
1465 * @fs_info:    the filesystem
1466 * @space_info: space info we want to allocate from
1467 * @orig_bytes: number of bytes we want
1468 * @flush:      whether or not we can flush to make our reservation
1469 *
1470 * This will reserve orig_bytes number of bytes from the space info associated
1471 * with the block_rsv.  If there is not enough space it will make an attempt to
1472 * flush out space to make room.  It will do this by flushing delalloc if
1473 * possible or committing the transaction.  If flush is 0 then no attempts to
1474 * regain reservations will be made and this will fail if there is not enough
1475 * space already.
1476 */
1477static int __reserve_bytes(struct btrfs_fs_info *fs_info,
1478                           struct btrfs_space_info *space_info, u64 orig_bytes,
1479                           enum btrfs_reserve_flush_enum flush)
1480{
1481        struct work_struct *async_work;
1482        struct reserve_ticket ticket;
1483        u64 start_ns = 0;
1484        u64 used;
1485        int ret = 0;
1486        bool pending_tickets;
1487
1488        ASSERT(orig_bytes);
1489        ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
1490
1491        if (flush == BTRFS_RESERVE_FLUSH_DATA)
1492                async_work = &fs_info->async_data_reclaim_work;
1493        else
1494                async_work = &fs_info->async_reclaim_work;
1495
1496        spin_lock(&space_info->lock);
1497        ret = -ENOSPC;
1498        used = btrfs_space_info_used(space_info, true);
1499
1500        /*
1501         * We don't want NO_FLUSH allocations to jump everybody, they can
1502         * generally handle ENOSPC in a different way, so treat them the same as
1503         * normal flushers when it comes to skipping pending tickets.
1504         */
1505        if (is_normal_flushing(flush) || (flush == BTRFS_RESERVE_NO_FLUSH))
1506                pending_tickets = !list_empty(&space_info->tickets) ||
1507                        !list_empty(&space_info->priority_tickets);
1508        else
1509                pending_tickets = !list_empty(&space_info->priority_tickets);
1510
1511        /*
1512         * Carry on if we have enough space (short-circuit) OR call
1513         * can_overcommit() to ensure we can overcommit to continue.
1514         */
1515        if (!pending_tickets &&
1516            ((used + orig_bytes <= space_info->total_bytes) ||
1517             btrfs_can_overcommit(fs_info, space_info, orig_bytes, flush))) {
1518                btrfs_space_info_update_bytes_may_use(fs_info, space_info,
1519                                                      orig_bytes);
1520                ret = 0;
1521        }
1522
1523        /*
1524         * If we couldn't make a reservation then setup our reservation ticket
1525         * and kick the async worker if it's not already running.
1526         *
1527         * If we are a priority flusher then we just need to add our ticket to
1528         * the list and we will do our own flushing further down.
1529         */
1530        if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
1531                ticket.bytes = orig_bytes;
1532                ticket.error = 0;
1533                space_info->reclaim_size += ticket.bytes;
1534                init_waitqueue_head(&ticket.wait);
1535                ticket.steal = can_steal(flush);
1536                if (trace_btrfs_reserve_ticket_enabled())
1537                        start_ns = ktime_get_ns();
1538
1539                if (flush == BTRFS_RESERVE_FLUSH_ALL ||
1540                    flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
1541                    flush == BTRFS_RESERVE_FLUSH_DATA) {
1542                        list_add_tail(&ticket.list, &space_info->tickets);
1543                        if (!space_info->flush) {
1544                                /*
1545                                 * We were forced to add a reserve ticket, so
1546                                 * our preemptive flushing is unable to keep
1547                                 * up.  Clamp down on the threshold for the
1548                                 * preemptive flushing in order to keep up with
1549                                 * the workload.
1550                                 */
1551                                maybe_clamp_preempt(fs_info, space_info);
1552
1553                                space_info->flush = 1;
1554                                trace_btrfs_trigger_flush(fs_info,
1555                                                          space_info->flags,
1556                                                          orig_bytes, flush,
1557                                                          "enospc");
1558                                queue_work(system_unbound_wq, async_work);
1559                        }
1560                } else {
1561                        list_add_tail(&ticket.list,
1562                                      &space_info->priority_tickets);
1563                }
1564        } else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
1565                used += orig_bytes;
1566                /*
1567                 * We will do the space reservation dance during log replay,
1568                 * which means we won't have fs_info->fs_root set, so don't do
1569                 * the async reclaim as we will panic.
1570                 */
1571                if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
1572                    !work_busy(&fs_info->preempt_reclaim_work) &&
1573                    need_preemptive_reclaim(fs_info, space_info)) {
1574                        trace_btrfs_trigger_flush(fs_info, space_info->flags,
1575                                                  orig_bytes, flush, "preempt");
1576                        queue_work(system_unbound_wq,
1577                                   &fs_info->preempt_reclaim_work);
1578                }
1579        }
1580        spin_unlock(&space_info->lock);
1581        if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
1582                return ret;
1583
1584        return handle_reserve_ticket(fs_info, space_info, &ticket, start_ns,
1585                                     orig_bytes, flush);
1586}
1587
1588/**
1589 * Trye to reserve metadata bytes from the block_rsv's space
1590 *
1591 * @fs_info:    the filesystem
1592 * @block_rsv:  block_rsv we're allocating for
1593 * @orig_bytes: number of bytes we want
1594 * @flush:      whether or not we can flush to make our reservation
1595 *
1596 * This will reserve orig_bytes number of bytes from the space info associated
1597 * with the block_rsv.  If there is not enough space it will make an attempt to
1598 * flush out space to make room.  It will do this by flushing delalloc if
1599 * possible or committing the transaction.  If flush is 0 then no attempts to
1600 * regain reservations will be made and this will fail if there is not enough
1601 * space already.
1602 */
1603int btrfs_reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
1604                                 struct btrfs_block_rsv *block_rsv,
1605                                 u64 orig_bytes,
1606                                 enum btrfs_reserve_flush_enum flush)
1607{
1608        int ret;
1609
1610        ret = __reserve_bytes(fs_info, block_rsv->space_info, orig_bytes, flush);
1611        if (ret == -ENOSPC) {
1612                trace_btrfs_space_reservation(fs_info, "space_info:enospc",
1613                                              block_rsv->space_info->flags,
1614                                              orig_bytes, 1);
1615
1616                if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
1617                        btrfs_dump_space_info(fs_info, block_rsv->space_info,
1618                                              orig_bytes, 0);
1619        }
1620        return ret;
1621}
1622
1623/**
1624 * Try to reserve data bytes for an allocation
1625 *
1626 * @fs_info: the filesystem
1627 * @bytes:   number of bytes we need
1628 * @flush:   how we are allowed to flush
1629 *
1630 * This will reserve bytes from the data space info.  If there is not enough
1631 * space then we will attempt to flush space as specified by flush.
1632 */
1633int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
1634                             enum btrfs_reserve_flush_enum flush)
1635{
1636        struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
1637        int ret;
1638
1639        ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
1640               flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE);
1641        ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
1642
1643        ret = __reserve_bytes(fs_info, data_sinfo, bytes, flush);
1644        if (ret == -ENOSPC) {
1645                trace_btrfs_space_reservation(fs_info, "space_info:enospc",
1646                                              data_sinfo->flags, bytes, 1);
1647                if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
1648                        btrfs_dump_space_info(fs_info, data_sinfo, bytes, 0);
1649        }
1650        return ret;
1651}
1652