Commit 9aa06c76 authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
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btrfs: count extents before taking inode's spinlock when reserving metadata 



When reserving metadata space for delalloc (and direct IO too), at
btrfs_delalloc_reserve_metadata(), there's no need to count the number of
extents while holding the inode's spinlock, since that does not require
access to any field of the inode.

This section of code can be called concurrently, when we have direct IO
writes against different file ranges that don't increase the inode's
i_size, so it's beneficial to shorten the critical section by counting
the number of extents before taking the inode's spinlock.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 5758d1bd

fs/btrfs/delalloc-space.c

+1 −1
Original line number Diff line number Diff line
@@ -358,8 +358,8 @@ int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes, 
	 * racing with an ordered completion or some such that would think it

	 * needs to free the reservation we just made.

	 */

	spin_lock(&inode->lock);

	nr_extents = count_max_extents(fs_info, num_bytes);

	spin_lock(&inode->lock);

	btrfs_mod_outstanding_extents(inode, nr_extents);

	inode->csum_bytes += disk_num_bytes;

	btrfs_calculate_inode_block_rsv_size(fs_info, inode);