mm: shmem: remove unnecessary warning in shmem_writepage()

JIRA: https://issues.redhat.com/browse/RHEL-84184

This patch is a backport of the following upstream commit:
commit adae46a
Author: Ricardo Cañuelo Navarro <rcn@igalia.com>
Date:   Wed Feb 26 13:26:27 2025 +0100

    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/8afe1f7f-31a2-4fc0-1fbd-f9ba8a116fe3@google.com/

    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 <rcn@igalia.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>
    Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
    Cc: Florent Revest <revest@chromium.org>
    Cc: Christian Brauner <brauner@kernel.org>
    Cc: David Hildenbrand <david@redhat.com>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: Florent Revest <revest@chromium.org>
    Cc: Luis Chamberalin <mcgrof@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Rafael Aquini <raquini@redhat.com>

Author: Rafael Aquini

mm/shmem.c

@@ -1440,7 +1440,7 @@ 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)