FSDAX page refcounts are 1-based, rather than 0-based: if refcount is
1, then the page is freed. The FSDAX pages can be pinned through GUP,
then they will be unpinned via unpin_user_page() using a folio variant
to put the page, however, folio variants did not consider this special
case, the result will be to miss a wakeup event (like the user of
__fuse_dax_break_layouts()).
Fixes: d8ddc099c6b3 ("mm/gup: Add gup_put_folio()")
Signed-off-by: Muchun Song <songmuc...@bytedance.com>
---
include/linux/mm.h | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 517f9deba56f..32aaa7b06f5a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1223,6 +1223,9 @@ static inline __must_check bool try_get_page(struct page
*page)
*/
static inline void folio_put(struct folio *folio)
{
+ if (put_devmap_managed_page(&folio->page))
+ return;
+
if (folio_put_testzero(folio))
__folio_put(folio);
}
@@ -1243,8 +1246,13 @@ static inline void folio_put(struct folio *folio)
*/
static inline void folio_put_refs(struct folio *folio, int refs)
{
- if (folio_ref_sub_and_test(folio, refs))
- __folio_put(folio);
+ /*
+ * For fsdax managed pages we need to catch refcount transition
+ * from 2 to 1:
+ */
+ if (refs > 1)
+ folio_ref_sub(folio, refs - 1);
+ folio_put(folio);
}
void release_pages(struct page **pages, int nr);
@@ -1268,15 +1276,7 @@ static inline void folios_put(struct folio **folios,
unsigned int nr)
static inline void put_page(struct page *page)
{
- struct folio *folio = page_folio(page);
-
- /*
- * For some devmap managed pages we need to catch refcount transition
- * from 2 to 1:
- */
- if (put_devmap_managed_page(&folio->page))
- return;
- folio_put(folio);
+ folio_put(page_folio(page));
}
/*
--
2.11.0
