From: Filipe Manana <fdmanana@xxxxxxxx> [ Upstream commit 20903032cd9f0260b99aeab92e6540f0350e4a23 ] During the nocow writeback path, we currently iterate the rbtree of block groups twice: once for checking if the target block group is RO with the call to btrfs_extent_readonly()), and once again for getting a nocow reference on the block group with a call to btrfs_inc_nocow_writers(). Since btrfs_inc_nocow_writers() already returns false when the target block group is RO, remove the call to btrfs_extent_readonly(). Not only we avoid searching the blocks group rbtree twice, it also helps reduce contention on the lock that protects it (specially since it is a spin lock and not a read-write lock). That may make a noticeable difference on very large filesystems, with thousands of allocated block groups. Reviewed-by: Anand Jain <anand.jain@xxxxxxxxxx> Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/btrfs/inode.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index ad34c5a09bef..02c4bfa515fb 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1657,9 +1657,6 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, */ btrfs_release_path(path); - /* If extent is RO, we must COW it */ - if (btrfs_extent_readonly(fs_info, disk_bytenr)) - goto out_check; ret = btrfs_cross_ref_exist(root, ino, found_key.offset - extent_offset, disk_bytenr, false); @@ -1706,6 +1703,7 @@ static noinline int run_delalloc_nocow(struct btrfs_inode *inode, WARN_ON_ONCE(freespace_inode); goto out_check; } + /* If the extent's block group is RO, we must COW */ if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr)) goto out_check; nocow = true; -- 2.30.1
