mm: shmem: remove unnecessary warning in shmem_writepage()

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/[email protected]/

Link: https://lkml.kernel.org/r/20250226-20250221-warning-in-shmem_writepage-v1-1-5ad19420e17e@igalia.com
Fixes: 9a976f0 ("shmem: skip page split if we're not reclaiming")
Signed-off-by: Ricardo Cañuelo Navarro <[email protected]>
Reported-by: Pengfei Xu <[email protected]>
Closes: https://lore.kernel.org/lkml/[email protected]/ [1]
Suggested-by: Hugh Dickins <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Cc: Florent Revest <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Florent Revest <[email protected]>
Cc: Luis Chamberalin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: r-c-n

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)