Commit e30729d4 authored by Naohiro Aota's avatar Naohiro Aota Committed by David Sterba
Browse files

btrfs: zoned: properly take lock to read/update block group's zoned variables 



__btrfs_add_free_space_zoned() references and modifies bg's alloc_offset,
ro, and zone_unusable, but without taking the lock. It is mostly safe
because they monotonically increase (at least for now) and this function is
mostly called by a transaction commit, which is serialized by itself.

Still, taking the lock is a safer and correct option and I'm going to add a
change to reset zone_unusable while a block group is still alive. So, add
locking around the operations.

Fixes: 169e0da9 ("btrfs: zoned: track unusable bytes for zones")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 008e2512

fs/btrfs/free-space-cache.c

+8 −6
Original line number Diff line number Diff line
@@ -2697,15 +2697,16 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, 
	u64 offset = bytenr - block_group->start;

	u64 to_free, to_unusable;

	int bg_reclaim_threshold = 0;

	bool initial = ((size == block_group->length) && (block_group->alloc_offset == 0));

	bool initial;

	u64 reclaimable_unusable;



	WARN_ON(!initial && offset + size > block_group->zone_capacity);

	spin_lock(&block_group->lock);



	initial = ((size == block_group->length) && (block_group->alloc_offset == 0));

	WARN_ON(!initial && offset + size > block_group->zone_capacity);

	if (!initial)

		bg_reclaim_threshold = READ_ONCE(sinfo->bg_reclaim_threshold);



	spin_lock(&ctl->tree_lock);

	if (!used)

		to_free = size;

	else if (initial)
@@ -2718,7 +2719,9 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, 
		to_free = offset + size - block_group->alloc_offset;

	to_unusable = size - to_free;



	spin_lock(&ctl->tree_lock);

	ctl->free_space += to_free;

	spin_unlock(&ctl->tree_lock);

	/*

	 * If the block group is read-only, we should account freed space into

	 * bytes_readonly.
@@ -2727,11 +2730,8 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, 
		block_group->zone_unusable += to_unusable;

		WARN_ON(block_group->zone_unusable > block_group->length);

	}

	spin_unlock(&ctl->tree_lock);

	if (!used) {

		spin_lock(&block_group->lock);

		block_group->alloc_offset -= size;

		spin_unlock(&block_group->lock);

	}



	reclaimable_unusable = block_group->zone_unusable -
@@ -2745,6 +2745,8 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, 
		btrfs_mark_bg_to_reclaim(block_group);

	}



	spin_unlock(&block_group->lock);



	return 0;

}