On 16.05.2018 11:28, Ethan Lien wrote:
> In nocow path, we check if the extent is snapshotted in
> btrfs_cross_ref_exist(). We can do the similar check earlier and avoid
> unnecessary search into extent tree.
>
> Signed-off-by: Ethan Lien <ethanlien@xxxxxxxxxxxx>
If this is supposed to be a performance improvement do you have any
measurements that prove that this is indeed the case?
> ---
> fs/btrfs/inode.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d241285a0d2a..96927f2ccd4b 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -1373,6 +1373,9 @@ static noinline int run_delalloc_nocow(struct inode *inode,
> btrfs_file_extent_encryption(leaf, fi) ||
> btrfs_file_extent_other_encoding(leaf, fi))
> goto out_check;
> + if (btrfs_file_extent_generation(leaf, fi) <=
> + btrfs_root_last_snapshot(&root->root_item))
> + goto out_check;
> if (extent_type == BTRFS_FILE_EXTENT_REG && !force)
> goto out_check;
> if (btrfs_extent_readonly(fs_info, disk_bytenr))
> @@ -7368,6 +7371,10 @@ noinline int can_nocow_extent(struct inode *inode, u64 offset, u64 *len,
> btrfs_file_extent_other_encoding(leaf, fi))
> goto out;
>
> + if (btrfs_file_extent_generation(leaf, fi) <=
> + btrfs_root_last_snapshot(&root->root_item))
> + goto out;
> +
> backref_offset = btrfs_file_extent_offset(leaf, fi);
>
> if (orig_start) {
>
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