[PATCH v4 10/17] mm/huge_memory: remove outdated VM_WARN_ON_ONCE_PAGE from unmap_page()

David Hildenbrand
2022-04-28T08:38:55Z

We can already theoretically fail to unmap (still having page_mapped()) in
case arch_unmap_one() fails, which can happen on sparc. Failures to
unmap are handled gracefully, just as if there are other references on
the target page: freezing the refcount in split_huge_page_to_list()
will fail if still mapped and we'll simply remap.

In commit 504e070dc08f ("mm: thp: replace DEBUG_VM BUG with VM_WARN when
unmap fails for split") we already converted to VM_WARN_ON_ONCE_PAGE,
let's get rid of it completely now.

This is a preparation for making try_to_migrate() fail on anonymous pages
with GUP pins, which will make this VM_WARN_ON_ONCE_PAGE trigger more
frequently.

Reported-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/huge_memory.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 04c9446b87a8..cb5bcd833d9e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2240,8 +2240,6 @@ static void unmap_page(struct page *page)
try_to_migrate(folio, ttu_flags);
else
try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
-
- VM_WARN_ON_ONCE_PAGE(page_mapped(page), page);
}

static void remap_page(struct folio *folio, unsigned long nr)
--
2.35.1