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btrfs: shorten critical section in btrfs_preempt_reclaim_metadata_space()

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We are doing a lot of small calculations and assignments while holding the
space_info's spinlock, which is a heavily used lock for space reservation
and flushing. There's no point in holding the lock for so long when all we
want is to call need_preemptive_reclaim() and get a consistent value for a
couple of counters from the space_info. Instead, grab the counters into
local variables, release the lock and then use the local variables.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana
2025-10-17 17:07:22 +01:00
committed by David Sterba
parent 8ab2b8bdbe
commit 4ddb077378
1 changed files with 7 additions and 6 deletions
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13
fs/btrfs/space-info.c
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@@ -1263,7 +1263,10 @@ static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
u64 delalloc_size = 0;
u64 to_reclaim, block_rsv_size;
const u64 global_rsv_size = btrfs_block_rsv_reserved(global_rsv);
const u64 bytes_may_use = space_info->bytes_may_use;
const u64 bytes_pinned = space_info->bytes_pinned;
spin_unlock(&space_info->lock);
/*
* We don't have a precise counter for the metadata being
* reserved for delalloc, so we'll approximate it by subtracting
@@ -1275,8 +1278,8 @@ static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
btrfs_block_rsv_reserved(delayed_block_rsv) +
btrfs_block_rsv_reserved(delayed_refs_rsv) +
btrfs_block_rsv_reserved(trans_rsv);
if (block_rsv_size < space_info->bytes_may_use)
delalloc_size = space_info->bytes_may_use - block_rsv_size;
if (block_rsv_size < bytes_may_use)
delalloc_size = bytes_may_use - block_rsv_size;
/*
* We don't want to include the global_rsv in our calculation,
@@ -1293,10 +1296,10 @@ static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
if (delalloc_size > block_rsv_size) {
to_reclaim = delalloc_size;
flush = FLUSH_DELALLOC;
} else if (space_info->bytes_pinned >
} else if (bytes_pinned >
(btrfs_block_rsv_reserved(delayed_block_rsv) +
btrfs_block_rsv_reserved(delayed_refs_rsv))) {
to_reclaim = space_info->bytes_pinned;
to_reclaim = bytes_pinned;
flush = COMMIT_TRANS;
} else if (btrfs_block_rsv_reserved(delayed_block_rsv) >
btrfs_block_rsv_reserved(delayed_refs_rsv)) {
@@ -1307,8 +1310,6 @@ static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
flush = FLUSH_DELAYED_REFS_NR;
}
spin_unlock(&space_info->lock);
loops++;
/*