[PATCH] btrfs: defrag: fix check to see if next extent can be defragged too

[PATCH] btrfs: defrag: fix check to see if next extent can be defragged too

[fdmanana]

From: Filipe Manana <fdmanana@suse.com>

We want to check if the next extent is at maximum capacity but we are
passing the current extent map to get_extent_max_capacity() and not
the next extent map. For example if the current extent is compressed (its
maximum capacity is 128K) and the next extent is uncompressed (its
maximum capacity is 128M), then we can bail out and not defrag the next
extent too - when for example the next extent as a size of 128K, is
uncompressed, and the extent threshold is >= 256K.

Fixes: 979b25c300db ("btrfs: defrag: don't defrag extents which are already at max capacity")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/defrag.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/defrag.c b/fs/btrfs/defrag.c
index 75c87aee5de9..7010d714cfe1 100644
--- a/fs/btrfs/defrag.c
+++ b/fs/btrfs/defrag.c
@@ -811,7 +811,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em,
 	 * If the next extent is at its max capacity, defragging current extent
 	 * makes no sense, as the total number of extents won't change.
 	 */
-	if (next->len >= get_extent_max_capacity(fs_info, em))
+	if (next->len >= get_extent_max_capacity(fs_info, next))
 		goto out;
 	/* Skip older extent */
 	if (next->generation < newer_than)
-- 
2.53.0

Re: [PATCH] btrfs: defrag: fix check to see if next extent can be defragged too

[Qu Wenruo]

在 2026/10/8 01:50, fdmanana@kernel.org 写道:
> From: Filipe Manana <fdmanana@suse.com>
> 
> We want to check if the next extent is at maximum capacity but we are
> passing the current extent map to get_extent_max_capacity() and not
> the next extent map. For example if the current extent is compressed (its
> maximum capacity is 128K) and the next extent is uncompressed (its
> maximum capacity is 128M), then we can bail out and not defrag the next
> extent too - when for example the next extent as a size of 128K, is
> uncompressed, and the extent threshold is >= 256K.
> 
> Fixes: 979b25c300db ("btrfs: defrag: don't defrag extents which are already at max capacity")
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Reviewed-by: Qu Wenruo <wqu@suse.com>

Thanks,
Qu

> ---
>   fs/btrfs/defrag.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/defrag.c b/fs/btrfs/defrag.c
> index 75c87aee5de9..7010d714cfe1 100644
> --- a/fs/btrfs/defrag.c
> +++ b/fs/btrfs/defrag.c
> @@ -811,7 +811,7 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em,
>   	 * If the next extent is at its max capacity, defragging current extent
>   	 * makes no sense, as the total number of extents won't change.
>   	 */
> -	if (next->len >= get_extent_max_capacity(fs_info, em))
> +	if (next->len >= get_extent_max_capacity(fs_info, next))
>   		goto out;
>   	/* Skip older extent */
>   	if (next->generation < newer_than)