[PATCH v2 1/2] mm/vmscan: fix hwpoisoned large folio handling in shrink_folio_list

[Jinjiang Tu <tujinjiang@huawei.com>]

In shrink_folio_list(), the hwpoisoned folio may be large folio, which
can't be handled by unmap_poisoned_folio().

Since UCE is rare in real world, and race with reclaimation is more rare,
just skipping the hwpoisoned large folio is enough. memory_failure() will
handle it if the UCE is triggered again.

Fixes: 1b0449544c64 ("mm/vmscan: don't try to reclaim hwpoison folio")
Reported-by: syzbot+3b220254df55d8ca8a61@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68412d57.050a0220.2461cf.000e.GAE@google.com/
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
---
 mm/vmscan.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f8dfd2864bbf..424412680cfc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1138,6 +1138,14 @@ static unsigned int shrink_folio_list(struct list_head *folio_list,
 			goto keep;
 
 		if (folio_contain_hwpoisoned_page(folio)) {
+			/*
+			 * unmap_poisoned_folio() can't handle large
+			 * folio, just skip it. memory_failure() will
+			 * handle it if the UCE is triggered again.
+			 */
+			if (folio_test_large(folio))
+				goto keep_locked;
+
 			unmap_poisoned_folio(folio, folio_pfn(folio), false);
 			folio_unlock(folio);
 			folio_put(folio);
-- 
2.43.0