[PATCH v5 4/5] mm: memory_failure: Generalize extra_pins handling to all MF_DELAYED cases

[Lisa Wang <wyihan@google.com>]

Generalize extra_pins handling to all MF_DELAYED cases not only
shmem_mapping.

If MF_DELAYED is returned, the filemap continues to hold refcounts on the
folio. Hence, take that into account when checking for extra refcounts.

As clarified in an earlier patch, a return value of MF_DELAYED implies that
the page still has elevated refcounts. Hence, set extra_pins to true if the
return value is MF_DELAYED. This is aligned with the implementation in
me_swapcache_dirty(), where, if a folio is still in the swap cache, ret is
set to MF_DELAYED and extra_pins is set to true.

Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Lisa Wang <wyihan@google.com>
---
 mm/memory-failure.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 37ea23489b75..c7a00c7be368 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1039,18 +1039,14 @@ static int me_pagecache_clean(struct page_state *ps, struct page *p)
 		goto out;
 	}
 
-	/*
-	 * The shmem page is kept in page cache instead of truncating
-	 * so is expected to have an extra refcount after error-handling.
-	 */
-	extra_pins = shmem_mapping(mapping);
-
 	/*
 	 * Truncation is a bit tricky. Enable it per file system for now.
 	 *
 	 * Open: to take i_rwsem or not for this? Right now we don't.
 	 */
 	ret = truncate_error_folio(folio, page_to_pfn(p), mapping);
+
+	extra_pins = ret == MF_DELAYED;
 	if (has_extra_refcount(ps, p, extra_pins))
 		ret = MF_FAILED;
 

-- 
2.55.0.766.g2966f0265a-goog