Re: [PATCH] xfs: fix reclaimed page accounting in xfs_buf_free

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Aug 21, 2026 at 05:03:37PM -0500, Eric Sandeen wrote:
> To obtain nr. of pages in "size" bytes, we need howmany(size, PAGE_SIZE)
> not howmany(size, PAGE_SHIFT). This over-reports reclaim by orders of
> magnitude, up to 4096x on a 64k page system.
> 
> Fixes: e2874632a621 ("xfs: use vmalloc instead of vm_map_area for buffer backing memory")
> Cc: stable@vger.kernel.org # v6.15+
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Yikes.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_buf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index 1a5340baeabf..8256c1d13ce2 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -139,7 +139,7 @@ xfs_buf_free(
>  	ASSERT(list_empty(&bp->b_lru));
>  
>  	if (!xfs_buftarg_is_mem(bp->b_target) && size >= PAGE_SIZE)
> -		mm_account_reclaimed_pages(howmany(size, PAGE_SHIFT));
> +		mm_account_reclaimed_pages(howmany(size, PAGE_SIZE));
>  
>  	if (is_vmalloc_addr(bp->b_addr))
>  		vfree(bp->b_addr);
> 
>