Re: [PATCH 4/6] btrfs: defrag: use auto kfree in defrag_one_range() for folios array

On Thu, Jun 25, 2026 at 08:20:14PM +0100, [email protected] wrote:
> From: Filipe Manana <[email protected]>
> 
> Use AUTO_KFREE() for the folios array, avoiding two kfree() calls, one of
> them in a very specific error path.
> 
> Signed-off-by: Filipe Manana <[email protected]>
> ---
>  fs/btrfs/defrag.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/btrfs/defrag.c b/fs/btrfs/defrag.c
> index ad1d04d8f165..e454b59d6477 100644
> --- a/fs/btrfs/defrag.c
> +++ b/fs/btrfs/defrag.c
> @@ -1169,7 +1169,7 @@ static int defrag_one_range(struct btrfs_inode *inode, u64 start, u32 len,
>  	struct defrag_target_range *entry;
>  	struct defrag_target_range *tmp;
>  	LIST_HEAD(target_list);
> -	struct folio **folios;
> +	struct folio AUTO_KFREE(*folios);
>  	const u32 sectorsize = inode->root->fs_info->sectorsize;
>  	u64 cur = start;
>  	const unsigned int nr_pages = ((start + len - 1) >> PAGE_SHIFT) -
> @@ -1196,10 +1196,8 @@ static int defrag_one_range(struct btrfs_inode *inode, u64 start, u32 len,
>  	 * range or the extent lock.
>  	 */
>  	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, start, len);
> -	if (ret < 0) {
> -		kfree(folios);
> +	if (ret < 0)
>  		return ret;
> -	}
>  
>  	/* Prepare all pages */
>  	for (int i = 0; cur < start + len && i < nr_pages; i++) {
> @@ -1251,7 +1249,6 @@ static int defrag_one_range(struct btrfs_inode *inode, u64 start, u32 len,
>  		folio_unlock(folios[i]);
>  		folio_put(folios[i]);
>  	}
> -	kfree(folios);

There's non-trivial work following this freeing, down from
btrfs_delalloc_release_space(). I consider using auto freeing in such
cases as anti-pattern and have skipped converting them.

In this function there's only one early exit from the function so the
auto freeing is underused, I'd rather not do it.

>  	btrfs_delalloc_release_extents(inode, len);
>  	if (last_defrag_end < start + len)
>  		btrfs_delalloc_release_space(inode, data_reserved, last_defrag_end,
> -- 
> 2.47.2
>