mm: shmem: remove unnecessary warning in shmem_writepage()

[PATCH] mm: shmem: remove unnecessary warning in shmem_writepage()

Posted by Ricardo Cañuelo Navarro 9 months, 3 weeks ago

Although the scenario where shmem_writepage() is called with info->flags
& VM_LOCKED is unlikely to happen, it's still possible, as evidenced by
syzbot [1]. However, the warning in this case isn't necessary because
the situation is already handled correctly [2].

[2] https://lore.kernel.org/lkml/8afe1f7f-31a2-4fc0-1fbd-f9ba8a116fe3@google.com/

Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Closes: https://lore.kernel.org/lkml/ZZ9PShXjKJkVelNm@xpf.sh.intel.com/ [1]
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: Florent Revest <revest@chromium.org>
Signed-off-by: Ricardo Cañuelo Navarro <rcn@igalia.com>
Fixes: 9a976f0c847b ("shmem: skip page split if we're not reclaiming")
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4ea6109a80431e5eeae15278064d5c86412f9fc9..a5eaad03038e8ca56a54d096159892e01c7a5bfe 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1548,7 +1548,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	if (WARN_ON_ONCE(!wbc->for_reclaim))
 		goto redirty;
 
-	if (WARN_ON_ONCE((info->flags & VM_LOCKED) || sbinfo->noswap))
+	if ((info->flags & VM_LOCKED) || sbinfo->noswap)
 		goto redirty;
 
 	if (!total_swap_pages)

---
base-commit: ac9c34d1e45a4c25174ced4fc0cfc33ff3ed08c7
change-id: 20250226-20250221-warning-in-shmem_writepage-e7f8f273317c

Cheers,
Ricardo

Re: [PATCH] mm: shmem: remove unnecessary warning in shmem_writepage()

Posted by Baolin Wang 9 months, 3 weeks ago


On 2025/2/26 20:26, Ricardo Cañuelo Navarro wrote:
> Although the scenario where shmem_writepage() is called with info->flags
> & VM_LOCKED is unlikely to happen, it's still possible, as evidenced by
> syzbot [1]. However, the warning in this case isn't necessary because
> the situation is already handled correctly [2].
> 
> [2] https://lore.kernel.org/lkml/8afe1f7f-31a2-4fc0-1fbd-f9ba8a116fe3@google.com/
> 
> Reported-by: Pengfei Xu <pengfei.xu@intel.com>
> Closes: https://lore.kernel.org/lkml/ZZ9PShXjKJkVelNm@xpf.sh.intel.com/ [1]
> Suggested-by: Hugh Dickins <hughd@google.com>
> Cc: Florent Revest <revest@chromium.org>
> Signed-off-by: Ricardo Cañuelo Navarro <rcn@igalia.com>
> Fixes: 9a976f0c847b ("shmem: skip page split if we're not reclaiming")
> ---

LGTM.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

>   mm/shmem.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 4ea6109a80431e5eeae15278064d5c86412f9fc9..a5eaad03038e8ca56a54d096159892e01c7a5bfe 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1548,7 +1548,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
>   	if (WARN_ON_ONCE(!wbc->for_reclaim))
>   		goto redirty;
>   
> -	if (WARN_ON_ONCE((info->flags & VM_LOCKED) || sbinfo->noswap))
> +	if ((info->flags & VM_LOCKED) || sbinfo->noswap)
>   		goto redirty;
>   
>   	if (!total_swap_pages)
> 
> ---
> base-commit: ac9c34d1e45a4c25174ced4fc0cfc33ff3ed08c7
> change-id: 20250226-20250221-warning-in-shmem_writepage-e7f8f273317c
> 
> Cheers,
> Ricardo
>