[PATCH v4 5/5] mm: filter out swapin error entry in shmem mapping

[Miaohe Lin]

There might be swapin error entries in shmem mapping. Filter them out to
avoid "Bad swap file entry" complaint.

Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 mm/madvise.c    | 5 ++++-
 mm/swap_state.c | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index a42165bc4735..31582b6ff551 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -248,10 +248,13 @@ static void force_shm_swapin_readahead(struct vm_area_struct *vma,
 
 		if (!xa_is_value(page))
 			continue;
+		swap = radix_to_swp_entry(page);
+		/* There might be swapin error entries in shmem mapping. */
+		if (non_swap_entry(swap))
+			continue;
 		xas_pause(&xas);
 		rcu_read_unlock();
 
-		swap = radix_to_swp_entry(page);
 		page = read_swap_cache_async(swap, GFP_HIGHUSER_MOVABLE,
 					     NULL, 0, false, &splug);
 		if (page)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index b9e4ed2e90bf..778d57d2d92d 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -410,6 +410,9 @@ struct page *find_get_incore_page(struct address_space *mapping, pgoff_t index)
 		return NULL;
 
 	swp = radix_to_swp_entry(page);
+	/* There might be swapin error entries in shmem mapping. */
+	if (non_swap_entry(swp))
+		return NULL;
 	/* Prevent swapoff from happening to us */
 	si = get_swap_device(swp);
 	if (!si)
-- 
2.23.0