[PATCH v5 3/5] mm: shmem: Update shmem handler to the MF_DELAYED definition

To align with the definition of MF_DELAYED, update
shmem_error_remove_folio() to return MF_DELAYED.

shmem handles memory failures but defers the actual file truncation. The
function's return value should therefore be MF_DELAYED to accurately
reflect the state.

Currently, this logical error does not cause a bug, because:

- For shmem folios, folio->private is not set.
- As a result, filemap_release_folio() is a no-op and returns true.
- This, in turn, causes truncate_error_folio() to incorrectly return
  MF_RECOVERED.
- The caller then treats MF_RECOVERED as a success condition, masking the
  issue.

The previous patch relays MF_DELAYED to the caller of
truncate_error_folio() before any logging, so returning MF_DELAYED from
shmem_error_remove_folio() will retain the original behavior of not
adding any logs.

The return value of truncate_error_folio() is consumed in action_result(),
which treats MF_DELAYED the same way as MF_RECOVERED, hence action_result()
also returns the same thing after this change.

Acked-by: David Hildenbrand (Arm) <[email protected]>
Acked-by: Miaohe Lin <[email protected]>
Reviewed-by: Ackerley Tng <[email protected]>
Signed-off-by: Lisa Wang <[email protected]>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 774f4b18ff5c..d6f94786e709 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -5136,7 +5136,7 @@ static void __init shmem_destroy_inodecache(void)
 static int shmem_error_remove_folio(struct address_space *mapping,
 				   struct folio *folio)
 {
-	return 0;
+	return MF_DELAYED;
 }
 
 static const struct address_space_operations shmem_aops = {

-- 
2.55.0.766.g2966f0265a-goog