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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 
 #include "misc.h"
 #include "ctree.h"
 #include "space-info.h"
 #include "sysfs.h"
 #include "volumes.h"
 #include "free-space-cache.h"
 #include "ordered-data.h"
 #include "transaction.h"
 #include "block-group.h"
 #include "zoned.h"
 
 /*
  * HOW DOES SPACE RESERVATION WORK
  *
  * If you want to know about delalloc specifically, there is a separate comment
  * for that with the delalloc code.  This comment is about how the whole system
  * works generally.
  *
  * BASIC CONCEPTS
  *
  *   1) space_info.  This is the ultimate arbiter of how much space we can use.
  *   There's a description of the bytes_ fields with the struct declaration,
  *   refer to that for specifics on each field.  Suffice it to say that for
  *   reservations we care about total_bytes - SUM(space_info->bytes_) when
  *   determining if there is space to make an allocation.  There is a space_info
  *   for METADATA, SYSTEM, and DATA areas.
  *
  *   2) block_rsv's.  These are basically buckets for every different type of
  *   metadata reservation we have.  You can see the comment in the block_rsv
  *   code on the rules for each type, but generally block_rsv->reserved is how
  *   much space is accounted for in space_info->bytes_may_use.
  *
  *   3) btrfs_calc*_size.  These are the worst case calculations we used based
  *   on the number of items we will want to modify.  We have one for changing
  *   items, and one for inserting new items.  Generally we use these helpers to
  *   determine the size of the block reserves, and then use the actual bytes
  *   values to adjust the space_info counters.
  *
  * MAKING RESERVATIONS, THE NORMAL CASE
  *
  *   We call into either btrfs_reserve_data_bytes() or
  *   btrfs_reserve_metadata_bytes(), depending on which we're looking for, with
  *   num_bytes we want to reserve.
  *
  *   ->reserve
  *     space_info->bytes_may_reserve += num_bytes
  *
  *   ->extent allocation
  *     Call btrfs_add_reserved_bytes() which does
  *     space_info->bytes_may_reserve -= num_bytes
  *     space_info->bytes_reserved += extent_bytes
  *
  *   ->insert reference
  *     Call btrfs_update_block_group() which does
  *     space_info->bytes_reserved -= extent_bytes
  *     space_info->bytes_used += extent_bytes
  *
  * MAKING RESERVATIONS, FLUSHING NORMALLY (non-priority)
  *
  *   Assume we are unable to simply make the reservation because we do not have
  *   enough space
  *
  *   -> __reserve_bytes
  *     create a reserve_ticket with ->bytes set to our reservation, add it to
  *     the tail of space_info->tickets, kick async flush thread
  *
  *   ->handle_reserve_ticket
  *     wait on ticket->wait for ->bytes to be reduced to 0, or ->error to be set
  *     on the ticket.
  *
  *   -> btrfs_async_reclaim_metadata_space/btrfs_async_reclaim_data_space
  *     Flushes various things attempting to free up space.
  *
  *   -> btrfs_try_granting_tickets()
  *     This is called by anything that either subtracts space from
  *     space_info->bytes_may_use, ->bytes_pinned, etc, or adds to the
  *     space_info->total_bytes.  This loops through the ->priority_tickets and
  *     then the ->tickets list checking to see if the reservation can be
  *     completed.  If it can the space is added to space_info->bytes_may_use and
  *     the ticket is woken up.
  *
  *   -> ticket wakeup
  *     Check if ->bytes == 0, if it does we got our reservation and we can carry
  *     on, if not return the appropriate error (ENOSPC, but can be EINTR if we
  *     were interrupted.)
  *
  * MAKING RESERVATIONS, FLUSHING HIGH PRIORITY
  *
  *   Same as the above, except we add ourselves to the
  *   space_info->priority_tickets, and we do not use ticket->wait, we simply
  *   call flush_space() ourselves for the states that are safe for us to call
  *   without deadlocking and hope for the best.
  *
  * THE FLUSHING STATES
  *
  *   Generally speaking we will have two cases for each state, a "nice" state
  *   and a "ALL THE THINGS" state.  In btrfs we delay a lot of work in order to
  *   reduce the locking over head on the various trees, and even to keep from
  *   doing any work at all in the case of delayed refs.  Each of these delayed
  *   things however hold reservations, and so letting them run allows us to
  *   reclaim space so we can make new reservations.
  *
  *   FLUSH_DELAYED_ITEMS
  *     Every inode has a delayed item to update the inode.  Take a simple write
  *     for example, we would update the inode item at write time to update the
  *     mtime, and then again at finish_ordered_io() time in order to update the
  *     isize or bytes.  We keep these delayed items to coalesce these operations
  *     into a single operation done on demand.  These are an easy way to reclaim
  *     metadata space.
  *
  *   FLUSH_DELALLOC
  *     Look at the delalloc comment to get an idea of how much space is reserved
  *     for delayed allocation.  We can reclaim some of this space simply by
  *     running delalloc, but usually we need to wait for ordered extents to
  *     reclaim the bulk of this space.
  *
  *   FLUSH_DELAYED_REFS
  *     We have a block reserve for the outstanding delayed refs space, and every
  *     delayed ref operation holds a reservation.  Running these is a quick way
  *     to reclaim space, but we want to hold this until the end because COW can
  *     churn a lot and we can avoid making some extent tree modifications if we
  *     are able to delay for as long as possible.
  *
  *   ALLOC_CHUNK
  *     We will skip this the first time through space reservation, because of
  *     overcommit and we don't want to have a lot of useless metadata space when
  *     our worst case reservations will likely never come true.
  *
  *   RUN_DELAYED_IPUTS
  *     If we're freeing inodes we're likely freeing checksums, file extent
  *     items, and extent tree items.  Loads of space could be freed up by these
  *     operations, however they won't be usable until the transaction commits.
  *
  *   COMMIT_TRANS
  *     This will commit the transaction.  Historically we had a lot of logic
  *     surrounding whether or not we'd commit the transaction, but this waits born
  *     out of a pre-tickets era where we could end up committing the transaction
  *     thousands of times in a row without making progress.  Now thanks to our
  *     ticketing system we know if we're not making progress and can error
  *     everybody out after a few commits rather than burning the disk hoping for
  *     a different answer.
  *
  * OVERCOMMIT
  *
  *   Because we hold so many reservations for metadata we will allow you to
  *   reserve more space than is currently free in the currently allocate
  *   metadata space.  This only happens with metadata, data does not allow
  *   overcommitting.
  *
  *   You can see the current logic for when we allow overcommit in
  *   btrfs_can_overcommit(), but it only applies to unallocated space.  If there
  *   is no unallocated space to be had, all reservations are kept within the
  *   free space in the allocated metadata chunks.
  *
  *   Because of overcommitting, you generally want to use the
  *   btrfs_can_overcommit() logic for metadata allocations, as it does the right
  *   thing with or without extra unallocated space.
  */
 
 u64 __pure btrfs_space_info_used(struct btrfs_space_info *s_info,
               bool may_use_included)
 {
     ASSERT(s_info);
     return s_info->bytes_used + s_info->bytes_reserved +
         s_info->bytes_pinned + s_info->bytes_readonly +
         s_info->bytes_zone_unusable +
         (may_use_included ? s_info->bytes_may_use : 0);
 }
 
 /*
  * after adding space to the filesystem, we need to clear the full flags
  * on all the space infos.
  */
 void btrfs_clear_space_info_full(struct btrfs_fs_info *info)
 {
     struct list_head *head = &info->space_info;
     struct btrfs_space_info *found;
 
     list_for_each_entry(found, head, list)
         found->full = 0;
 }
 
 /*
  * Block groups with more than this value (percents) of unusable space will be
  * scheduled for background reclaim.
  */
 #define BTRFS_DEFAULT_ZONED_RECLAIM_THRESH          (75)
 
 /*
  * Calculate chunk size depending on volume type (regular or zoned).
  */
 static u64 calc_chunk_size(const struct btrfs_fs_info *fs_info, u64 flags)
 {
     if (btrfs_is_zoned(fs_info))
         return fs_info->zone_size;
 
     ASSERT(flags & BTRFS_BLOCK_GROUP_TYPE_MASK);
 
     if (flags & BTRFS_BLOCK_GROUP_DATA)
         return BTRFS_MAX_DATA_CHUNK_SIZE;
     else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
         return SZ_32M;
 
     /* Handle BTRFS_BLOCK_GROUP_METADATA */
     if (fs_info->fs_devices->total_rw_bytes > 50ULL * SZ_1G)
         return SZ_1G;
 
     return SZ_256M;
 }
 
 /*
  * Update default chunk size.
  */
 void btrfs_update_space_info_chunk_size(struct btrfs_space_info *space_info,
                     u64 chunk_size)
 {
     WRITE_ONCE(space_info->chunk_size, chunk_size);
 }
 
 static int create_space_info(struct btrfs_fs_info *info, u64 flags)
 {
 
     struct btrfs_space_info *space_info;
     int i;
     int ret;
 
     space_info = kzalloc(sizeof(*space_info), GFP_NOFS);
     if (!space_info)
         return -ENOMEM;
 
     for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
         INIT_LIST_HEAD(&space_info->block_groups[i]);
     init_rwsem(&space_info->groups_sem);
     spin_lock_init(&space_info->lock);
     space_info->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
     space_info->force_alloc = CHUNK_ALLOC_NO_FORCE;
     INIT_LIST_HEAD(&space_info->ro_bgs);
     INIT_LIST_HEAD(&space_info->tickets);
     INIT_LIST_HEAD(&space_info->priority_tickets);
     space_info->clamp = 1;
     btrfs_update_space_info_chunk_size(space_info, calc_chunk_size(info, flags));
 
     if (btrfs_is_zoned(info))
         space_info->bg_reclaim_threshold = BTRFS_DEFAULT_ZONED_RECLAIM_THRESH;
 
     ret = btrfs_sysfs_add_space_info_type(info, space_info);
     if (ret)
         return ret;
 
     list_add(&space_info->list, &info->space_info);
     if (flags & BTRFS_BLOCK_GROUP_DATA)
         info->data_sinfo = space_info;
 
     return ret;
 }
 
 int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 {
     struct btrfs_super_block *disk_super;
     u64 features;
     u64 flags;
     int mixed = 0;
     int ret;
 
     disk_super = fs_info->super_copy;
     if (!btrfs_super_root(disk_super))
         return -EINVAL;
 
     features = btrfs_super_incompat_flags(disk_super);
     if (features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
         mixed = 1;
 
     flags = BTRFS_BLOCK_GROUP_SYSTEM;
     ret = create_space_info(fs_info, flags);
     if (ret)
         goto out;
 
     if (mixed) {
         flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
         ret = create_space_info(fs_info, flags);
     } else {
         flags = BTRFS_BLOCK_GROUP_METADATA;
         ret = create_space_info(fs_info, flags);
         if (ret)
             goto out;
 
         flags = BTRFS_BLOCK_GROUP_DATA;
         ret = create_space_info(fs_info, flags);
     }
 out:
     return ret;
 }
 
 void btrfs_update_space_info(struct btrfs_fs_info *info, u64 flags,
                  u64 total_bytes, u64 bytes_used,
                  u64 bytes_readonly, u64 bytes_zone_unusable,
                  bool active, struct btrfs_space_info **space_info)
 {
     struct btrfs_space_info *found;
     int factor;
 
     factor = btrfs_bg_type_to_factor(flags);
 
     found = btrfs_find_space_info(info, flags);
     ASSERT(found);
     spin_lock(&found->lock);
     found->total_bytes += total_bytes;
     if (active)
         found->active_total_bytes += total_bytes;
     found->disk_total += total_bytes * factor;
     found->bytes_used += bytes_used;
     found->disk_used += bytes_used * factor;
     found->bytes_readonly += bytes_readonly;
     found->bytes_zone_unusable += bytes_zone_unusable;
     if (total_bytes > 0)
         found->full = 0;
     btrfs_try_granting_tickets(info, found);
     spin_unlock(&found->lock);
     *space_info = found;
 }
 
 struct btrfs_space_info *btrfs_find_space_info(struct btrfs_fs_info *info,
                            u64 flags)
 {
     struct list_head *head = &info->space_info;
     struct btrfs_space_info *found;
 
     flags &= BTRFS_BLOCK_GROUP_TYPE_MASK;
 
     list_for_each_entry(found, head, list) {
         if (found->flags & flags)
             return found;
     }
     return NULL;
 }
 
 static u64 calc_available_free_space(struct btrfs_fs_info *fs_info,
               struct btrfs_space_info *space_info,
               enum btrfs_reserve_flush_enum flush)
 {
     u64 profile;
     u64 avail;
     int factor;
 
     if (space_info->flags & BTRFS_BLOCK_GROUP_SYSTEM)
         profile = btrfs_system_alloc_profile(fs_info);
     else
         profile = btrfs_metadata_alloc_profile(fs_info);
 
     avail = atomic64_read(&fs_info->free_chunk_space);
 
     /*
      * If we have dup, raid1 or raid10 then only half of the free
      * space is actually usable.  For raid56, the space info used
      * doesn't include the parity drive, so we don't have to
      * change the math
      */
     factor = btrfs_bg_type_to_factor(profile);
     avail = div_u64(avail, factor);
 
     /*
      * If we aren't flushing all things, let us overcommit up to
      * 1/2th of the space. If we can flush, don't let us overcommit
      * too much, let it overcommit up to 1/8 of the space.
      */
     if (flush == BTRFS_RESERVE_FLUSH_ALL)
         avail >>= 3;
     else
         avail >>= 1;
     return avail;
 }
 
 static inline u64 writable_total_bytes(struct btrfs_fs_info *fs_info,
                        struct btrfs_space_info *space_info)
 {
     /*
      * On regular filesystem, all total_bytes are always writable. On zoned
      * filesystem, there may be a limitation imposed by max_active_zones.
      * For metadata allocation, we cannot finish an existing active block
      * group to avoid a deadlock. Thus, we need to consider only the active
      * groups to be writable for metadata space.
      */
     if (!btrfs_is_zoned(fs_info) || (space_info->flags & BTRFS_BLOCK_GROUP_DATA))
         return space_info->total_bytes;
 
     return space_info->active_total_bytes;
 }
 
 int btrfs_can_overcommit(struct btrfs_fs_info *fs_info,
              struct btrfs_space_info *space_info, u64 bytes,
              enum btrfs_reserve_flush_enum flush)
 {
     u64 avail;
     u64 used;
 
     /* Don't overcommit when in mixed mode */
     if (space_info->flags & BTRFS_BLOCK_GROUP_DATA)
         return 0;
 
     used = btrfs_space_info_used(space_info, true);
     if (btrfs_is_zoned(fs_info) && (space_info->flags & BTRFS_BLOCK_GROUP_METADATA))
         avail = 0;
     else
         avail = calc_available_free_space(fs_info, space_info, flush);
 
     if (used + bytes < writable_total_bytes(fs_info, space_info) + avail)
         return 1;
     return 0;
 }
 
 static void remove_ticket(struct btrfs_space_info *space_info,
               struct reserve_ticket *ticket)
 {
     if (!list_empty(&ticket->list)) {
         list_del_init(&ticket->list);
         ASSERT(space_info->reclaim_size >= ticket->bytes);
         space_info->reclaim_size -= ticket->bytes;
     }
 }
 
 /*
  * This is for space we already have accounted in space_info->bytes_may_use, so
  * basically when we're returning space from block_rsv's.
  */
 void btrfs_try_granting_tickets(struct btrfs_fs_info *fs_info,
                 struct btrfs_space_info *space_info)
 {
     struct list_head *head;
     enum btrfs_reserve_flush_enum flush = BTRFS_RESERVE_NO_FLUSH;
 
     lockdep_assert_held(&space_info->lock);
 
     head = &space_info->priority_tickets;
 again:
     while (!list_empty(head)) {
         struct reserve_ticket *ticket;
         u64 used = btrfs_space_info_used(space_info, true);
 
         ticket = list_first_entry(head, struct reserve_ticket, list);
 
         /* Check and see if our ticket can be satisfied now. */
         if ((used + ticket->bytes <= writable_total_bytes(fs_info, space_info)) ||
             btrfs_can_overcommit(fs_info, space_info, ticket->bytes,
                      flush)) {
             btrfs_space_info_update_bytes_may_use(fs_info,
                                   space_info,
                                   ticket->bytes);
             remove_ticket(space_info, ticket);
             ticket->bytes = 0;
             space_info->tickets_id++;
             wake_up(&ticket->wait);
         } else {
             break;
         }
     }
 
     if (head == &space_info->priority_tickets) {
         head = &space_info->tickets;
         flush = BTRFS_RESERVE_FLUSH_ALL;
         goto again;
     }
 }
 
 #define DUMP_BLOCK_RSV(fs_info, rsv_name)               \
 do {                                    \
     struct btrfs_block_rsv *__rsv = &(fs_info)->rsv_name;       \
     spin_lock(&__rsv->lock);                    \
     btrfs_info(fs_info, #rsv_name ": size %llu reserved %llu",  \
            __rsv->size, __rsv->reserved);           \
     spin_unlock(&__rsv->lock);                  \
 } while (0)
 
 static void __btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
                     struct btrfs_space_info *info)
 {
     lockdep_assert_held(&info->lock);
 
     /* The free space could be negative in case of overcommit */
     btrfs_info(fs_info, "space_info %llu has %lld free, is %sfull",
            info->flags,
            (s64)(info->total_bytes - btrfs_space_info_used(info, true)),
            info->full ? "" : "not ");
     btrfs_info(fs_info,
         "space_info total=%llu, used=%llu, pinned=%llu, reserved=%llu, may_use=%llu, readonly=%llu zone_unusable=%llu",
         info->total_bytes, info->bytes_used, info->bytes_pinned,
         info->bytes_reserved, info->bytes_may_use,
         info->bytes_readonly, info->bytes_zone_unusable);
 
     DUMP_BLOCK_RSV(fs_info, global_block_rsv);
     DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
     DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
     DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
     DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
 
 }
 
 void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
                struct btrfs_space_info *info, u64 bytes,
                int dump_block_groups)
 {
     struct btrfs_block_group *cache;
     int index = 0;
 
     spin_lock(&info->lock);
     __btrfs_dump_space_info(fs_info, info);
     spin_unlock(&info->lock);
 
     if (!dump_block_groups)
         return;
 
     down_read(&info->groups_sem);
 again:
     list_for_each_entry(cache, &info->block_groups[index], list) {
         spin_lock(&cache->lock);
         btrfs_info(fs_info,
             "block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %llu zone_unusable %s",
             cache->start, cache->length, cache->used, cache->pinned,
             cache->reserved, cache->zone_unusable,
             cache->ro ? "[readonly]" : "");
         spin_unlock(&cache->lock);
         btrfs_dump_free_space(cache, bytes);
     }
     if (++index < BTRFS_NR_RAID_TYPES)
         goto again;
     up_read(&info->groups_sem);
 }
 
 static inline u64 calc_reclaim_items_nr(struct btrfs_fs_info *fs_info,
                     u64 to_reclaim)
 {
     u64 bytes;
     u64 nr;
 
     bytes = btrfs_calc_insert_metadata_size(fs_info, 1);
     nr = div64_u64(to_reclaim, bytes);
     if (!nr)
         nr = 1;
     return nr;
 }
 
 #define EXTENT_SIZE_PER_ITEM    SZ_256K
 
 /*
  * shrink metadata reservation for delalloc
  */
 static void shrink_delalloc(struct btrfs_fs_info *fs_info,
                 struct btrfs_space_info *space_info,
                 u64 to_reclaim, bool wait_ordered,
                 bool for_preempt)
 {
     struct btrfs_trans_handle *trans;
     u64 delalloc_bytes;
     u64 ordered_bytes;
     u64 items;
     long time_left;
     int loops;
 
     delalloc_bytes = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
     ordered_bytes = percpu_counter_sum_positive(&fs_info->ordered_bytes);
     if (delalloc_bytes == 0 && ordered_bytes == 0)
         return;
 
     /* Calc the number of the pages we need flush for space reservation */
     if (to_reclaim == U64_MAX) {
         items = U64_MAX;
     } else {
         /*
          * to_reclaim is set to however much metadata we need to
          * reclaim, but reclaiming that much data doesn't really track
          * exactly.  What we really want to do is reclaim full inode's
          * worth of reservations, however that's not available to us
          * here.  We will take a fraction of the delalloc bytes for our
          * flushing loops and hope for the best.  Delalloc will expand
          * the amount we write to cover an entire dirty extent, which
          * will reclaim the metadata reservation for that range.  If
          * it's not enough subsequent flush stages will be more
          * aggressive.
          */
         to_reclaim = max(to_reclaim, delalloc_bytes >> 3);
         items = calc_reclaim_items_nr(fs_info, to_reclaim) * 2;
     }
 
     trans = current->journal_info;
 
     /*
      * If we are doing more ordered than delalloc we need to just wait on
      * ordered extents, otherwise we'll waste time trying to flush delalloc
      * that likely won't give us the space back we need.
      */
     if (ordered_bytes > delalloc_bytes && !for_preempt)
         wait_ordered = true;
 
     loops = 0;
     while ((delalloc_bytes || ordered_bytes) && loops < 3) {
         u64 temp = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
         long nr_pages = min_t(u64, temp, LONG_MAX);
         int async_pages;
 
         btrfs_start_delalloc_roots(fs_info, nr_pages, true);
 
         /*
          * We need to make sure any outstanding async pages are now
          * processed before we continue.  This is because things like
          * sync_inode() try to be smart and skip writing if the inode is
          * marked clean.  We don't use filemap_fwrite for flushing
          * because we want to control how many pages we write out at a
          * time, thus this is the only safe way to make sure we've
          * waited for outstanding compressed workers to have started
          * their jobs and thus have ordered extents set up properly.
          *
          * This exists because we do not want to wait for each
          * individual inode to finish its async work, we simply want to
          * start the IO on everybody, and then come back here and wait
          * for all of the async work to catch up.  Once we're done with
          * that we know we'll have ordered extents for everything and we
          * can decide if we wait for that or not.
          *
          * If we choose to replace this in the future, make absolutely
          * sure that the proper waiting is being done in the async case,
          * as there have been bugs in that area before.
          */
         async_pages = atomic_read(&fs_info->async_delalloc_pages);
         if (!async_pages)
             goto skip_async;
 
         /*
          * We don't want to wait forever, if we wrote less pages in this
          * loop than we have outstanding, only wait for that number of
          * pages, otherwise we can wait for all async pages to finish
          * before continuing.
          */
         if (async_pages > nr_pages)
             async_pages -= nr_pages;
         else
             async_pages = 0;
         wait_event(fs_info->async_submit_wait,
                atomic_read(&fs_info->async_delalloc_pages) <=
                async_pages);
 skip_async:
         loops++;
         if (wait_ordered && !trans) {
             btrfs_wait_ordered_roots(fs_info, items, 0, (u64)-1);
         } else {
             time_left = schedule_timeout_killable(1);
             if (time_left)
                 break;
         }
 
         /*
          * If we are for preemption we just want a one-shot of delalloc
          * flushing so we can stop flushing if we decide we don't need
          * to anymore.
          */
         if (for_preempt)
             break;
 
         spin_lock(&space_info->lock);
         if (list_empty(&space_info->tickets) &&
             list_empty(&space_info->priority_tickets)) {
             spin_unlock(&space_info->lock);
             break;
         }
         spin_unlock(&space_info->lock);
 
         delalloc_bytes = percpu_counter_sum_positive(
                         &fs_info->delalloc_bytes);
         ordered_bytes = percpu_counter_sum_positive(
                         &fs_info->ordered_bytes);
     }
 }
 
 /*
  * Try to flush some data based on policy set by @state. This is only advisory
  * and may fail for various reasons. The caller is supposed to examine the
  * state of @space_info to detect the outcome.
  */
 static void flush_space(struct btrfs_fs_info *fs_info,
                struct btrfs_space_info *space_info, u64 num_bytes,
                enum btrfs_flush_state state, bool for_preempt)
 {
     struct btrfs_root *root = fs_info->tree_root;
     struct btrfs_trans_handle *trans;
     int nr;
     int ret = 0;
 
     switch (state) {
     case FLUSH_DELAYED_ITEMS_NR:
     case FLUSH_DELAYED_ITEMS:
         if (state == FLUSH_DELAYED_ITEMS_NR)
             nr = calc_reclaim_items_nr(fs_info, num_bytes) * 2;
         else
             nr = -1;
 
         trans = btrfs_join_transaction(root);
         if (IS_ERR(trans)) {
             ret = PTR_ERR(trans);
             break;
         }
         ret = btrfs_run_delayed_items_nr(trans, nr);
         btrfs_end_transaction(trans);
         break;
     case FLUSH_DELALLOC:
     case FLUSH_DELALLOC_WAIT:
     case FLUSH_DELALLOC_FULL:
         if (state == FLUSH_DELALLOC_FULL)
             num_bytes = U64_MAX;
         shrink_delalloc(fs_info, space_info, num_bytes,
                 state != FLUSH_DELALLOC, for_preempt);
         break;
     case FLUSH_DELAYED_REFS_NR:
     case FLUSH_DELAYED_REFS:
         trans = btrfs_join_transaction(root);
         if (IS_ERR(trans)) {
             ret = PTR_ERR(trans);
             break;
         }
         if (state == FLUSH_DELAYED_REFS_NR)
             nr = calc_reclaim_items_nr(fs_info, num_bytes);
         else
             nr = 0;
         btrfs_run_delayed_refs(trans, nr);
         btrfs_end_transaction(trans);
         break;
     case ALLOC_CHUNK:
     case ALLOC_CHUNK_FORCE:
         /*
          * For metadata space on zoned filesystem, reaching here means we
          * don't have enough space left in active_total_bytes. Try to
          * activate a block group first, because we may have inactive
          * block group already allocated.
          */
         ret = btrfs_zoned_activate_one_bg(fs_info, space_info, false);
         if (ret < 0)
             break;
         else if (ret == 1)
             break;
 
         trans = btrfs_join_transaction(root);
         if (IS_ERR(trans)) {
             ret = PTR_ERR(trans);
             break;
         }
         ret = btrfs_chunk_alloc(trans,
                 btrfs_get_alloc_profile(fs_info, space_info->flags),
                 (state == ALLOC_CHUNK) ? CHUNK_ALLOC_NO_FORCE :
                     CHUNK_ALLOC_FORCE);
         btrfs_end_transaction(trans);
 
         /*
          * For metadata space on zoned filesystem, allocating a new chunk
          * is not enough. We still need to activate the block * group.
          * Active the newly allocated block group by (maybe) finishing
          * a block group.
          */
         if (ret == 1) {
             ret = btrfs_zoned_activate_one_bg(fs_info, space_info, true);
             /*
              * Revert to the original ret regardless we could finish
              * one block group or not.
              */
             if (ret >= 0)
                 ret = 1;
         }
 
         if (ret > 0 || ret == -ENOSPC)
             ret = 0;
         break;
     case RUN_DELAYED_IPUTS:
         /*
          * If we have pending delayed iputs then we could free up a
          * bunch of pinned space, so make sure we run the iputs before
          * we do our pinned bytes check below.
          */
         btrfs_run_delayed_iputs(fs_info);
         btrfs_wait_on_delayed_iputs(fs_info);
         break;
     case COMMIT_TRANS:
         ASSERT(current->journal_info == NULL);
         trans = btrfs_join_transaction(root);
         if (IS_ERR(trans)) {
             ret = PTR_ERR(trans);
             break;
         }
         ret = btrfs_commit_transaction(trans);
         break;
     default:
         ret = -ENOSPC;
         break;
     }
 
     trace_btrfs_flush_space(fs_info, space_info->flags, num_bytes, state,
                 ret, for_preempt);
     return;
 }
 
 static inline u64
 btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
                  struct btrfs_space_info *space_info)
 {
     u64 used;
     u64 avail;
     u64 total;
     u64 to_reclaim = space_info->reclaim_size;
 
     lockdep_assert_held(&space_info->lock);
 
     avail = calc_available_free_space(fs_info, space_info,
                       BTRFS_RESERVE_FLUSH_ALL);
     used = btrfs_space_info_used(space_info, true);
 
     /*
      * We may be flushing because suddenly we have less space than we had
      * before, and now we're well over-committed based on our current free
      * space.  If that's the case add in our overage so we make sure to put
      * appropriate pressure on the flushing state machine.
      */
     total = writable_total_bytes(fs_info, space_info);
     if (total + avail < used)
         to_reclaim += used - (total + avail);
 
     return to_reclaim;
 }
 
 static bool need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
                     struct btrfs_space_info *space_info)
 {
     u64 global_rsv_size = fs_info->global_block_rsv.reserved;
     u64 ordered, delalloc;
     u64 total = writable_total_bytes(fs_info, space_info);
     u64 thresh;
     u64 used;
 
     thresh = div_factor_fine(total, 90);
 
     lockdep_assert_held(&space_info->lock);
 
     /* If we're just plain full then async reclaim just slows us down. */
     if ((space_info->bytes_used + space_info->bytes_reserved +
          global_rsv_size) >= thresh)
         return false;
 
     used = space_info->bytes_may_use + space_info->bytes_pinned;
 
     /* The total flushable belongs to the global rsv, don't flush. */
     if (global_rsv_size >= used)
         return false;
 
     /*
      * 128MiB is 1/4 of the maximum global rsv size.  If we have less than
      * that devoted to other reservations then there's no sense in flushing,
      * we don't have a lot of things that need flushing.
      */
     if (used - global_rsv_size <= SZ_128M)
         return false;
 
     /*
      * We have tickets queued, bail so we don't compete with the async
      * flushers.
      */
     if (space_info->reclaim_size)
         return false;
 
     /*
      * If we have over half of the free space occupied by reservations or
      * pinned then we want to start flushing.
      *
      * We do not do the traditional thing here, which is to say
      *
      *   if (used >= ((total_bytes + avail) / 2))
      *     return 1;
      *
      * because this doesn't quite work how we want.  If we had more than 50%
      * of the space_info used by bytes_used and we had 0 available we'd just
      * constantly run the background flusher.  Instead we want it to kick in
      * if our reclaimable space exceeds our clamped free space.
      *
      * Our clamping range is 2^1 -> 2^8.  Practically speaking that means
      * the following:
      *
      * Amount of RAM        Minimum threshold       Maximum threshold
      *
      *        256GiB                     1GiB                  128GiB
      *        128GiB                   512MiB                   64GiB
      *         64GiB                   256MiB                   32GiB
      *         32GiB                   128MiB                   16GiB
      *         16GiB                    64MiB                    8GiB
      *
      * These are the range our thresholds will fall in, corresponding to how
      * much delalloc we need for the background flusher to kick in.
      */
 
     thresh = calc_available_free_space(fs_info, space_info,
                        BTRFS_RESERVE_FLUSH_ALL);
     used = space_info->bytes_used + space_info->bytes_reserved +
            space_info->bytes_readonly + global_rsv_size;
     if (used < total)
         thresh += total - used;
     thresh >>= space_info->clamp;
 
     used = space_info->bytes_pinned;
 
     /*
      * If we have more ordered bytes than delalloc bytes then we're either
      * doing a lot of DIO, or we simply don't have a lot of delalloc waiting
      * around.  Preemptive flushing is only useful in that it can free up
      * space before tickets need to wait for things to finish.  In the case
      * of ordered extents, preemptively waiting on ordered extents gets us
      * nothing, if our reservations are tied up in ordered extents we'll
      * simply have to slow down writers by forcing them to wait on ordered
      * extents.
      *
      * In the case that ordered is larger than delalloc, only include the
      * block reserves that we would actually be able to directly reclaim
      * from.  In this case if we're heavy on metadata operations this will
      * clearly be heavy enough to warrant preemptive flushing.  In the case
      * of heavy DIO or ordered reservations, preemptive flushing will just
      * waste time and cause us to slow down.
      *
      * We want to make sure we truly are maxed out on ordered however, so
      * cut ordered in half, and if it's still higher than delalloc then we
      * can keep flushing.  This is to avoid the case where we start
      * flushing, and now delalloc == ordered and we stop preemptively
      * flushing when we could still have several gigs of delalloc to flush.
      */
     ordered = percpu_counter_read_positive(&fs_info->ordered_bytes) >> 1;
     delalloc = percpu_counter_read_positive(&fs_info->delalloc_bytes);
     if (ordered >= delalloc)
         used += fs_info->delayed_refs_rsv.reserved +
             fs_info->delayed_block_rsv.reserved;
     else
         used += space_info->bytes_may_use - global_rsv_size;
 
     return (used >= thresh && !btrfs_fs_closing(fs_info) &&
         !test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
 }
 
 static bool steal_from_global_rsv(struct btrfs_fs_info *fs_info,
                   struct btrfs_space_info *space_info,
                   struct reserve_ticket *ticket)
 {
     struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
     u64 min_bytes;
 
     if (!ticket->steal)
         return false;
 
     if (global_rsv->space_info != space_info)
         return false;
 
     spin_lock(&global_rsv->lock);
     min_bytes = div_factor(global_rsv->size, 1);
     if (global_rsv->reserved < min_bytes + ticket->bytes) {
         spin_unlock(&global_rsv->lock);
         return false;
     }
     global_rsv->reserved -= ticket->bytes;
     remove_ticket(space_info, ticket);
     ticket->bytes = 0;
     wake_up(&ticket->wait);
     space_info->tickets_id++;
     if (global_rsv->reserved < global_rsv->size)
         global_rsv->full = 0;
     spin_unlock(&global_rsv->lock);
 
     return true;
 }
 
 /*
  * maybe_fail_all_tickets - we've exhausted our flushing, start failing tickets
  * @fs_info - fs_info for this fs
  * @space_info - the space info we were flushing
  *
  * We call this when we've exhausted our flushing ability and haven't made
  * progress in satisfying tickets.  The reservation code handles tickets in
  * order, so if there is a large ticket first and then smaller ones we could
  * very well satisfy the smaller tickets.  This will attempt to wake up any
  * tickets in the list to catch this case.
  *
  * This function returns true if it was able to make progress by clearing out
  * other tickets, or if it stumbles across a ticket that was smaller than the
  * first ticket.
  */
 static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
                    struct btrfs_space_info *space_info)
 {
     struct reserve_ticket *ticket;
     u64 tickets_id = space_info->tickets_id;
     const bool aborted = BTRFS_FS_ERROR(fs_info);
 
     trace_btrfs_fail_all_tickets(fs_info, space_info);
 
     if (btrfs_test_opt(fs_info, ENOSPC_DEBUG)) {
         btrfs_info(fs_info, "cannot satisfy tickets, dumping space info");
         __btrfs_dump_space_info(fs_info, space_info);
     }
 
     while (!list_empty(&space_info->tickets) &&
            tickets_id == space_info->tickets_id) {
         ticket = list_first_entry(&space_info->tickets,
                       struct reserve_ticket, list);
 
         if (!aborted && steal_from_global_rsv(fs_info, space_info, ticket))
             return true;
 
         if (!aborted && btrfs_test_opt(fs_info, ENOSPC_DEBUG))
             btrfs_info(fs_info, "failing ticket with %llu bytes",
                    ticket->bytes);
 
         remove_ticket(space_info, ticket);
         if (aborted)
             ticket->error = -EIO;
         else
             ticket->error = -ENOSPC;
         wake_up(&ticket->wait);
 
         /*
          * We're just throwing tickets away, so more flushing may not
          * trip over btrfs_try_granting_tickets, so we need to call it
          * here to see if we can make progress with the next ticket in
          * the list.
          */
         if (!aborted)
             btrfs_try_granting_tickets(fs_info, space_info);
     }
     return (tickets_id != space_info->tickets_id);
 }
 
 /*
  * This is for normal flushers, we can wait all goddamned day if we want to.  We
  * will loop and continuously try to flush as long as we are making progress.
  * We count progress as clearing off tickets each time we have to loop.
  */
 static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
 {
     struct btrfs_fs_info *fs_info;
     struct btrfs_space_info *space_info;
     u64 to_reclaim;
     enum btrfs_flush_state flush_state;
     int commit_cycles = 0;
     u64 last_tickets_id;
 
     fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
     space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 
     spin_lock(&space_info->lock);
     to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
     if (!to_reclaim) {
         space_info->flush = 0;
         spin_unlock(&space_info->lock);
         return;
     }
     last_tickets_id = space_info->tickets_id;
     spin_unlock(&space_info->lock);
 
     flush_state = FLUSH_DELAYED_ITEMS_NR;
     do {
         flush_space(fs_info, space_info, to_reclaim, flush_state, false);
         spin_lock(&space_info->lock);
         if (list_empty(&space_info->tickets)) {
             space_info->flush = 0;
             spin_unlock(&space_info->lock);
             return;
         }
         to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info,
                                   space_info);
         if (last_tickets_id == space_info->tickets_id) {
             flush_state++;
         } else {
             last_tickets_id = space_info->tickets_id;
             flush_state = FLUSH_DELAYED_ITEMS_NR;
             if (commit_cycles)
                 commit_cycles--;
         }
 
         /*
          * We do not want to empty the system of delalloc unless we're
          * under heavy pressure, so allow one trip through the flushing
          * logic before we start doing a FLUSH_DELALLOC_FULL.
          */
         if (flush_state == FLUSH_DELALLOC_FULL && !commit_cycles)
             flush_state++;
 
         /*
          * We don't want to force a chunk allocation until we've tried
          * pretty hard to reclaim space.  Think of the case where we
          * freed up a bunch of space and so have a lot of pinned space
          * to reclaim.  We would rather use that than possibly create a
          * underutilized metadata chunk.  So if this is our first run
          * through the flushing state machine skip ALLOC_CHUNK_FORCE and
          * commit the transaction.  If nothing has changed the next go
          * around then we can force a chunk allocation.
          */
         if (flush_state == ALLOC_CHUNK_FORCE && !commit_cycles)
             flush_state++;
 
         if (flush_state > COMMIT_TRANS) {
             commit_cycles++;
             if (commit_cycles > 2) {
                 if (maybe_fail_all_tickets(fs_info, space_info)) {
                     flush_state = FLUSH_DELAYED_ITEMS_NR;
                     commit_cycles--;
                 } else {
                     space_info->flush = 0;
                 }
             } else {
                 flush_state = FLUSH_DELAYED_ITEMS_NR;
             }
         }
         spin_unlock(&space_info->lock);
     } while (flush_state <= COMMIT_TRANS);
 }
 
 /*
  * This handles pre-flushing of metadata space before we get to the point that
  * we need to start blocking threads on tickets.  The logic here is different
  * from the other flush paths because it doesn't rely on tickets to tell us how
  * much we need to flush, instead it attempts to keep us below the 80% full
  * watermark of space by flushing whichever reservation pool is currently the
  * largest.
  */
 static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
 {
     struct btrfs_fs_info *fs_info;
     struct btrfs_space_info *space_info;
     struct btrfs_block_rsv *delayed_block_rsv;
     struct btrfs_block_rsv *delayed_refs_rsv;
     struct btrfs_block_rsv *global_rsv;
     struct btrfs_block_rsv *trans_rsv;
     int loops = 0;
 
     fs_info = container_of(work, struct btrfs_fs_info,
                    preempt_reclaim_work);
     space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
     delayed_block_rsv = &fs_info->delayed_block_rsv;
     delayed_refs_rsv = &fs_info->delayed_refs_rsv;
     global_rsv = &fs_info->global_block_rsv;
     trans_rsv = &fs_info->trans_block_rsv;
 
     spin_lock(&space_info->lock);
     while (need_preemptive_reclaim(fs_info, space_info)) {
         enum btrfs_flush_state flush;
         u64 delalloc_size = 0;
         u64 to_reclaim, block_rsv_size;
         u64 global_rsv_size = global_rsv->reserved;
 
         loops++;
 
         /*
          * We don't have a precise counter for the metadata being
          * reserved for delalloc, so we'll approximate it by subtracting
          * out the block rsv's space from the bytes_may_use.  If that
          * amount is higher than the individual reserves, then we can
          * assume it's tied up in delalloc reservations.
          */
         block_rsv_size = global_rsv_size +
             delayed_block_rsv->reserved +
             delayed_refs_rsv->reserved +
             trans_rsv->reserved;
         if (block_rsv_size < space_info->bytes_may_use)
             delalloc_size = space_info->bytes_may_use - block_rsv_size;
 
         /*
          * We don't want to include the global_rsv in our calculation,
          * because that's space we can't touch.  Subtract it from the
          * block_rsv_size for the next checks.
          */
         block_rsv_size -= global_rsv_size;
 
         /*
          * We really want to avoid flushing delalloc too much, as it
          * could result in poor allocation patterns, so only flush it if
          * it's larger than the rest of the pools combined.
          */
         if (delalloc_size > block_rsv_size) {
             to_reclaim = delalloc_size;
             flush = FLUSH_DELALLOC;
         } else if (space_info->bytes_pinned >
                (delayed_block_rsv->reserved +
                 delayed_refs_rsv->reserved)) {
             to_reclaim = space_info->bytes_pinned;
             flush = COMMIT_TRANS;
         } else if (delayed_block_rsv->reserved >
                delayed_refs_rsv->reserved) {
             to_reclaim = delayed_block_rsv->reserved;
             flush = FLUSH_DELAYED_ITEMS_NR;
         } else {
             to_reclaim = delayed_refs_rsv->reserved;
             flush = FLUSH_DELAYED_REFS_NR;
         }
 
         spin_unlock(&space_info->lock);
 
         /*
          * We don't want to reclaim everything, just a portion, so scale
          * down the to_reclaim by 1/4.  If it takes us down to 0,
          * reclaim 1 items worth.
          */
         to_reclaim >>= 2;
         if (!to_reclaim)
             to_reclaim = btrfs_calc_insert_metadata_size(fs_info, 1);
         flush_space(fs_info, space_info, to_reclaim, flush, true);
         cond_resched();
         spin_lock(&space_info->lock);
     }
 
     /* We only went through once, back off our clamping. */
     if (loops == 1 && !space_info->reclaim_size)
         space_info->clamp = max(1, space_info->clamp - 1);
     trace_btrfs_done_preemptive_reclaim(fs_info, space_info);
     spin_unlock(&space_info->lock);
 }
 
 /*
  * FLUSH_DELALLOC_WAIT:
  *   Space is freed from flushing delalloc in one of two ways.
  *
  *   1) compression is on and we allocate less space than we reserved
  *   2) we are overwriting existing space
  *
  *   For #1 that extra space is reclaimed as soon as the delalloc pages are
  *   COWed, by way of btrfs_add_reserved_bytes() which adds the actual extent
  *   length to ->bytes_reserved, and subtracts the reserved space from
  *   ->bytes_may_use.
  *
  *   For #2 this is trickier.  Once the ordered extent runs we will drop the
  *   extent in the range we are overwriting, which creates a delayed ref for
  *   that freed extent.  This however is not reclaimed until the transaction
  *   commits, thus the next stages.
  *
  * RUN_DELAYED_IPUTS
  *   If we are freeing inodes, we want to make sure all delayed iputs have
  *   completed, because they could have been on an inode with i_nlink == 0, and
  *   thus have been truncated and freed up space.  But again this space is not
  *   immediately re-usable, it comes in the form of a delayed ref, which must be
  *   run and then the transaction must be committed.
  *
  * COMMIT_TRANS
  *   This is where we reclaim all of the pinned space generated by running the
  *   iputs
  *
  * ALLOC_CHUNK_FORCE
  *   For data we start with alloc chunk force, however we could have been full
  *   before, and then the transaction commit could have freed new block groups,
  *   so if we now have space to allocate do the force chunk allocation.
  */
 static const enum btrfs_flush_state data_flush_states[] = {
     FLUSH_DELALLOC_FULL,
     RUN_DELAYED_IPUTS,
     COMMIT_TRANS,
     ALLOC_CHUNK_FORCE,
 };
 
 static void btrfs_async_reclaim_data_space(struct work_struct *work)
 {
     struct btrfs_fs_info *fs_info;
     struct btrfs_space_info *space_info;
     u64 last_tickets_id;
     enum btrfs_flush_state flush_state = 0;
 
     fs_info = container_of(work, struct btrfs_fs_info, async_data_reclaim_work);
     space_info = fs_info->data_sinfo;
 
     spin_lock(&space_info->lock);
     if (list_empty(&space_info->tickets)) {
         space_info->flush = 0;
         spin_unlock(&space_info->lock);
         return;
     }
     last_tickets_id = space_info->tickets_id;
     spin_unlock(&space_info->lock);
 
     while (!space_info->full) {
         flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
         spin_lock(&space_info->lock);
         if (list_empty(&space_info->tickets)) {
             space_info->flush = 0;
             spin_unlock(&space_info->lock);
             return;
         }
 
         /* Something happened, fail everything and bail. */
         if (BTRFS_FS_ERROR(fs_info))
             goto aborted_fs;
         last_tickets_id = space_info->tickets_id;
         spin_unlock(&space_info->lock);
     }
 
     while (flush_state < ARRAY_SIZE(data_flush_states)) {
         flush_space(fs_info, space_info, U64_MAX,
                 data_flush_states[flush_state], false);
         spin_lock(&space_info->lock);
         if (list_empty(&space_info->tickets)) {
             space_info->flush = 0;
             spin_unlock(&space_info->lock);
             return;
         }
 
         if (last_tickets_id == space_info->tickets_id) {
             flush_state++;
         } else {
             last_tickets_id = space_info->tickets_id;
             flush_state = 0;
         }
 
         if (flush_state >= ARRAY_SIZE(data_flush_states)) {
             if (space_info->full) {
                 if (maybe_fail_all_tickets(fs_info, space_info))
                     flush_state = 0;
                 else
                     space_info->flush = 0;
             } else {
                 flush_state = 0;
             }
 
             /* Something happened, fail everything and bail. */
             if (BTRFS_FS_ERROR(fs_info))
                 goto aborted_fs;
 
         }
         spin_unlock(&space_info->lock);
     }
     return;
 
 aborted_fs:
     maybe_fail_all_tickets(fs_info, space_info);
     space_info->flush = 0;
     spin_unlock(&space_info->lock);
 }
 
 void btrfs_init_async_reclaim_work(struct btrfs_fs_info *fs_info)
 {
     INIT_WORK(&fs_info->async_reclaim_work, btrfs_async_reclaim_metadata_space);
     INIT_WORK(&fs_info->async_data_reclaim_work, btrfs_async_reclaim_data_space);
     INIT_WORK(&fs_info->preempt_reclaim_work,
           btrfs_preempt_reclaim_metadata_space);
 }
 
 static const enum btrfs_flush_state priority_flush_states[] = {
     FLUSH_DELAYED_ITEMS_NR,
     FLUSH_DELAYED_ITEMS,
     ALLOC_CHUNK,
 };
 
 static const enum btrfs_flush_state evict_flush_states[] = {
     FLUSH_DELAYED_ITEMS_NR,
     FLUSH_DELAYED_ITEMS,
     FLUSH_DELAYED_REFS_NR,
     FLUSH_DELAYED_REFS,
     FLUSH_DELALLOC,
     FLUSH_DELALLOC_WAIT,
     FLUSH_DELALLOC_FULL,
     ALLOC_CHUNK,
     COMMIT_TRANS,
 };
 
 static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
                 struct btrfs_space_info *space_info,
                 struct reserve_ticket *ticket,
                 const enum btrfs_flush_state *states,
                 int states_nr)
 {
     u64 to_reclaim;
     int flush_state = 0;
 
     spin_lock(&space_info->lock);
     to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info);
     /*
      * This is the priority reclaim path, so to_reclaim could be >0 still
      * because we may have only satisfied the priority tickets and still
      * left non priority tickets on the list.  We would then have
      * to_reclaim but ->bytes == 0.
      */
     if (ticket->bytes == 0) {
         spin_unlock(&space_info->lock);
         return;
     }
 
     while (flush_state < states_nr) {
         spin_unlock(&space_info->lock);
         flush_space(fs_info, space_info, to_reclaim, states[flush_state],
                 false);
         flush_state++;
         spin_lock(&space_info->lock);
         if (ticket->bytes == 0) {
             spin_unlock(&space_info->lock);
             return;
         }
     }
 
     /* Attempt to steal from the global rsv if we can. */
     if (!steal_from_global_rsv(fs_info, space_info, ticket)) {
         ticket->error = -ENOSPC;
         remove_ticket(space_info, ticket);
     }
 
     /*
      * We must run try_granting_tickets here because we could be a large
      * ticket in front of a smaller ticket that can now be satisfied with
      * the available space.
      */
     btrfs_try_granting_tickets(fs_info, space_info);
     spin_unlock(&space_info->lock);
 }
 
 static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
                     struct btrfs_space_info *space_info,
                     struct reserve_ticket *ticket)
 {
     spin_lock(&space_info->lock);
 
     /* We could have been granted before we got here. */
     if (ticket->bytes == 0) {
         spin_unlock(&space_info->lock);
         return;
     }
 
     while (!space_info->full) {
         spin_unlock(&space_info->lock);
         flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE, false);
         spin_lock(&space_info->lock);
         if (ticket->bytes == 0) {
             spin_unlock(&space_info->lock);
             return;
         }
     }
 
     ticket->error = -ENOSPC;
     remove_ticket(space_info, ticket);
     btrfs_try_granting_tickets(fs_info, space_info);
     spin_unlock(&space_info->lock);
 }
 
 static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
                 struct btrfs_space_info *space_info,
                 struct reserve_ticket *ticket)
 
 {
     DEFINE_WAIT(wait);
     int ret = 0;
 
     spin_lock(&space_info->lock);
     while (ticket->bytes > 0 && ticket->error == 0) {
         ret = prepare_to_wait_event(&ticket->wait, &wait, TASK_KILLABLE);
         if (ret) {
             /*
              * Delete us from the list. After we unlock the space
              * info, we don't want the async reclaim job to reserve
              * space for this ticket. If that would happen, then the
              * ticket's task would not known that space was reserved
              * despite getting an error, resulting in a space leak
              * (bytes_may_use counter of our space_info).
              */
             remove_ticket(space_info, ticket);
             ticket->error = -EINTR;
             break;
         }
         spin_unlock(&space_info->lock);
 
         schedule();
 
         finish_wait(&ticket->wait, &wait);
         spin_lock(&space_info->lock);
     }
     spin_unlock(&space_info->lock);
 }
 
 /**
  * Do the appropriate flushing and waiting for a ticket
  *
  * @fs_info:    the filesystem
  * @space_info: space info for the reservation
  * @ticket:     ticket for the reservation
  * @start_ns:   timestamp when the reservation started
  * @orig_bytes: amount of bytes originally reserved
  * @flush:      how much we can flush
  *
  * This does the work of figuring out how to flush for the ticket, waiting for
  * the reservation, and returning the appropriate error if there is one.
  */
 static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
                  struct btrfs_space_info *space_info,
                  struct reserve_ticket *ticket,
                  u64 start_ns, u64 orig_bytes,
                  enum btrfs_reserve_flush_enum flush)
 {
     int ret;
 
     switch (flush) {
     case BTRFS_RESERVE_FLUSH_DATA:
     case BTRFS_RESERVE_FLUSH_ALL:
     case BTRFS_RESERVE_FLUSH_ALL_STEAL:
         wait_reserve_ticket(fs_info, space_info, ticket);
         break;
     case BTRFS_RESERVE_FLUSH_LIMIT:
         priority_reclaim_metadata_space(fs_info, space_info, ticket,
                         priority_flush_states,
                         ARRAY_SIZE(priority_flush_states));
         break;
     case BTRFS_RESERVE_FLUSH_EVICT:
         priority_reclaim_metadata_space(fs_info, space_info, ticket,
                         evict_flush_states,
                         ARRAY_SIZE(evict_flush_states));
         break;
     case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
         priority_reclaim_data_space(fs_info, space_info, ticket);
         break;
     default:
         ASSERT(0);
         break;
     }
 
     ret = ticket->error;
     ASSERT(list_empty(&ticket->list));
     /*
      * Check that we can't have an error set if the reservation succeeded,
      * as that would confuse tasks and lead them to error out without
      * releasing reserved space (if an error happens the expectation is that
      * space wasn't reserved at all).
      */
     ASSERT(!(ticket->bytes == 0 && ticket->error));
     trace_btrfs_reserve_ticket(fs_info, space_info->flags, orig_bytes,
                    start_ns, flush, ticket->error);
     return ret;
 }
 
 /*
  * This returns true if this flush state will go through the ordinary flushing
  * code.
  */
 static inline bool is_normal_flushing(enum btrfs_reserve_flush_enum flush)
 {
     return  (flush == BTRFS_RESERVE_FLUSH_ALL) ||
         (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
 }
 
 static inline void maybe_clamp_preempt(struct btrfs_fs_info *fs_info,
                        struct btrfs_space_info *space_info)
 {
     u64 ordered = percpu_counter_sum_positive(&fs_info->ordered_bytes);
     u64 delalloc = percpu_counter_sum_positive(&fs_info->delalloc_bytes);
 
     /*
      * If we're heavy on ordered operations then clamping won't help us.  We
      * need to clamp specifically to keep up with dirty'ing buffered
      * writers, because there's not a 1:1 correlation of writing delalloc
      * and freeing space, like there is with flushing delayed refs or
      * delayed nodes.  If we're already more ordered than delalloc then
      * we're keeping up, otherwise we aren't and should probably clamp.
      */
     if (ordered < delalloc)
         space_info->clamp = min(space_info->clamp + 1, 8);
 }
 
 static inline bool can_steal(enum btrfs_reserve_flush_enum flush)
 {
     return (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
         flush == BTRFS_RESERVE_FLUSH_EVICT);
 }
 
 /**
  * Try to reserve bytes from the block_rsv's space
  *
  * @fs_info:    the filesystem
  * @space_info: space info we want to allocate from
  * @orig_bytes: number of bytes we want
  * @flush:      whether or not we can flush to make our reservation
  *
  * This will reserve orig_bytes number of bytes from the space info associated
  * with the block_rsv.  If there is not enough space it will make an attempt to
  * flush out space to make room.  It will do this by flushing delalloc if
  * possible or committing the transaction.  If flush is 0 then no attempts to
  * regain reservations will be made and this will fail if there is not enough
  * space already.
  */
 static int __reserve_bytes(struct btrfs_fs_info *fs_info,
                struct btrfs_space_info *space_info, u64 orig_bytes,
                enum btrfs_reserve_flush_enum flush)
 {
     struct work_struct *async_work;
     struct reserve_ticket ticket;
     u64 start_ns = 0;
     u64 used;
     int ret = 0;
     bool pending_tickets;
 
     ASSERT(orig_bytes);
     ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
 
     if (flush == BTRFS_RESERVE_FLUSH_DATA)
         async_work = &fs_info->async_data_reclaim_work;
     else
         async_work = &fs_info->async_reclaim_work;
 
     spin_lock(&space_info->lock);
     ret = -ENOSPC;
     used = btrfs_space_info_used(space_info, true);
 
     /*
      * We don't want NO_FLUSH allocations to jump everybody, they can
      * generally handle ENOSPC in a different way, so treat them the same as
      * normal flushers when it comes to skipping pending tickets.
      */
     if (is_normal_flushing(flush) || (flush == BTRFS_RESERVE_NO_FLUSH))
         pending_tickets = !list_empty(&space_info->tickets) ||
             !list_empty(&space_info->priority_tickets);
     else
         pending_tickets = !list_empty(&space_info->priority_tickets);
 
     /*
      * Carry on if we have enough space (short-circuit) OR call
      * can_overcommit() to ensure we can overcommit to continue.
      */
     if (!pending_tickets &&
         ((used + orig_bytes <= writable_total_bytes(fs_info, space_info)) ||
          btrfs_can_overcommit(fs_info, space_info, orig_bytes, flush))) {
         btrfs_space_info_update_bytes_may_use(fs_info, space_info,
                               orig_bytes);
         ret = 0;
     }
 
     /*
      * If we couldn't make a reservation then setup our reservation ticket
      * and kick the async worker if it's not already running.
      *
      * If we are a priority flusher then we just need to add our ticket to
      * the list and we will do our own flushing further down.
      */
     if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
         ticket.bytes = orig_bytes;
         ticket.error = 0;
         space_info->reclaim_size += ticket.bytes;
         init_waitqueue_head(&ticket.wait);
         ticket.steal = can_steal(flush);
         if (trace_btrfs_reserve_ticket_enabled())
             start_ns = ktime_get_ns();
 
         if (flush == BTRFS_RESERVE_FLUSH_ALL ||
             flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
             flush == BTRFS_RESERVE_FLUSH_DATA) {
             list_add_tail(&ticket.list, &space_info->tickets);
             if (!space_info->flush) {
                 /*
                  * We were forced to add a reserve ticket, so
                  * our preemptive flushing is unable to keep
                  * up.  Clamp down on the threshold for the
                  * preemptive flushing in order to keep up with
                  * the workload.
                  */
                 maybe_clamp_preempt(fs_info, space_info);
 
                 space_info->flush = 1;
                 trace_btrfs_trigger_flush(fs_info,
                               space_info->flags,
                               orig_bytes, flush,
                               "enospc");
                 queue_work(system_unbound_wq, async_work);
             }
         } else {
             list_add_tail(&ticket.list,
                       &space_info->priority_tickets);
         }
     } else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
         used += orig_bytes;
         /*
          * We will do the space reservation dance during log replay,
          * which means we won't have fs_info->fs_root set, so don't do
          * the async reclaim as we will panic.
          */
         if (!test_bit(BTRFS_FS_LOG_RECOVERING, &fs_info->flags) &&
             !work_busy(&fs_info->preempt_reclaim_work) &&
             need_preemptive_reclaim(fs_info, space_info)) {
             trace_btrfs_trigger_flush(fs_info, space_info->flags,
                           orig_bytes, flush, "preempt");
             queue_work(system_unbound_wq,
                    &fs_info->preempt_reclaim_work);
         }
     }
     spin_unlock(&space_info->lock);
     if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
         return ret;
 
     return handle_reserve_ticket(fs_info, space_info, &ticket, start_ns,
                      orig_bytes, flush);
 }
 
 /**
  * Trye to reserve metadata bytes from the block_rsv's space
  *
  * @fs_info:    the filesystem
  * @block_rsv:  block_rsv we're allocating for
  * @orig_bytes: number of bytes we want
  * @flush:      whether or not we can flush to make our reservation
  *
  * This will reserve orig_bytes number of bytes from the space info associated
  * with the block_rsv.  If there is not enough space it will make an attempt to
  * flush out space to make room.  It will do this by flushing delalloc if
  * possible or committing the transaction.  If flush is 0 then no attempts to
  * regain reservations will be made and this will fail if there is not enough
  * space already.
  */
 int btrfs_reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
                  struct btrfs_block_rsv *block_rsv,
                  u64 orig_bytes,
                  enum btrfs_reserve_flush_enum flush)
 {
     int ret;
 
     ret = __reserve_bytes(fs_info, block_rsv->space_info, orig_bytes, flush);
     if (ret == -ENOSPC) {
         trace_btrfs_space_reservation(fs_info, "space_info:enospc",
                           block_rsv->space_info->flags,
                           orig_bytes, 1);
 
         if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
             btrfs_dump_space_info(fs_info, block_rsv->space_info,
                           orig_bytes, 0);
     }
     return ret;
 }
 
 /**
  * Try to reserve data bytes for an allocation
  *
  * @fs_info: the filesystem
  * @bytes:   number of bytes we need
  * @flush:   how we are allowed to flush
  *
  * This will reserve bytes from the data space info.  If there is not enough
  * space then we will attempt to flush space as specified by flush.
  */
 int btrfs_reserve_data_bytes(struct btrfs_fs_info *fs_info, u64 bytes,
                  enum btrfs_reserve_flush_enum flush)
 {
     struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
     int ret;
 
     ASSERT(flush == BTRFS_RESERVE_FLUSH_DATA ||
            flush == BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE);
     ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
 
     ret = __reserve_bytes(fs_info, data_sinfo, bytes, flush);
     if (ret == -ENOSPC) {
         trace_btrfs_space_reservation(fs_info, "space_info:enospc",
                           data_sinfo->flags, bytes, 1);
         if (btrfs_test_opt(fs_info, ENOSPC_DEBUG))
             btrfs_dump_space_info(fs_info, data_sinfo, bytes, 0);
     }
     return ret;
 }

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