[PATCH v1] mm, hwpoison: enable error handling on shmem thp

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horigu...@nec.com>

Currently hwpoison code checks PageAnon() for thp and refuses to handle
errors on non-anonymous thps (just for historical reason).  We now
support non-anonymou thp like shmem one, so this patch suggests to enable
to handle shmem thps. Fortunately, we already have can_split_huge_page()
to check if a give thp is splittable, so this patch relies on it.

Signed-off-by: Naoya Horiguchi <naoya.horigu...@nec.com>
---
 mm/memory-failure.c | 34 +++++++++-------------------------
 1 file changed, 9 insertions(+), 25 deletions(-)

diff --git v5.11-rc6/mm/memory-failure.c v5.11-rc6_patched/mm/memory-failure.c
index e9481632fcd1..8c1575de0507 100644
--- v5.11-rc6/mm/memory-failure.c
+++ v5.11-rc6_patched/mm/memory-failure.c
@@ -956,20 +956,6 @@ static int __get_hwpoison_page(struct page *page)
 {
        struct page *head = compound_head(page);
 
-       if (!PageHuge(head) && PageTransHuge(head)) {
-               /*
-                * Non anonymous thp exists only in allocation/free time. We
-                * can't handle such a case correctly, so let's give it up.
-                * This should be better than triggering BUG_ON when kernel
-                * tries to touch the "partially handled" page.
-                */
-               if (!PageAnon(head)) {
-                       pr_err("Memory failure: %#lx: non anonymous thp\n",
-                               page_to_pfn(page));
-                       return 0;
-               }
-       }
-
        if (get_page_unless_zero(head)) {
                if (head == compound_head(page))
                        return 1;
@@ -1197,21 +1183,19 @@ static int identify_page_state(unsigned long pfn, 
struct page *p,
 
 static int try_to_split_thp_page(struct page *page, const char *msg)
 {
-       lock_page(page);
-       if (!PageAnon(page) || unlikely(split_huge_page(page))) {
-               unsigned long pfn = page_to_pfn(page);
+       struct page *head;
 
+       lock_page(page);
+       head = compound_head(page);
+       if (PageTransHuge(head) && can_split_huge_page(head, NULL) &&
+           !split_huge_page(page)) {
                unlock_page(page);
-               if (!PageAnon(page))
-                       pr_info("%s: %#lx: non anonymous thp\n", msg, pfn);
-               else
-                       pr_info("%s: %#lx: thp split failed\n", msg, pfn);
-               put_page(page);
-               return -EBUSY;
+               return 0;
        }
+       pr_info("%s: %#lx: thp split failed\n", msg, page_to_pfn(page));
        unlock_page(page);
-
-       return 0;
+       put_page(page);
+       return -EBUSY;
 }
 
 static int memory_failure_hugetlb(unsigned long pfn, int flags)
-- 
2.25.1