mm: delete __ClearPageWaiters()
The PG_waiters bit is not included in PAGE_FLAGS_CHECK_AT_FREE, and
vmscan.c's free_unref_page_list() callers rely on that not to generate
bad_page() alerts. So __page_cache_release(), put_pages_list() and
release_pages() (and presumably copy-and-pasted free_zone_device_page())
are redundant and misleading to make a special point of clearing it (as
the "__" implies, it could only safely be used on the freeing path).
Delete __ClearPageWaiters(). Remark on this in one of the "possible"
comments in folio_wake_bit(), and delete the superfluous comments.
Link: https://lkml.kernel.org/r/3eafa969-5b1a-accf-88fe-318784c791a@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index d2e6a79..98dfeff8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1185,24 +1185,17 @@ static void folio_wake_bit(struct folio *folio, int bit_nr)
}
/*
- * It is possible for other pages to have collided on the waitqueue
- * hash, so in that case check for a page match. That prevents a long-
- * term waiter
+ * It's possible to miss clearing waiters here, when we woke our page
+ * waiters, but the hashed waitqueue has waiters for other pages on it.
+ * That's okay, it's a rare case. The next waker will clear it.
*
- * It is still possible to miss a case here, when we woke page waiters
- * and removed them from the waitqueue, but there are still other
- * page waiters.
+ * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
+ * other), the flag may be cleared in the course of freeing the page;
+ * but that is not required for correctness.
*/
- if (!waitqueue_active(q) || !key.page_match) {
+ if (!waitqueue_active(q) || !key.page_match)
folio_clear_waiters(folio);
- /*
- * It's possible to miss clearing Waiters here, when we woke
- * our page waiters, but the hashed waitqueue has waiters for
- * other pages on it.
- *
- * That's okay, it's a rare case. The next waker will clear it.
- */
- }
+
spin_unlock_irqrestore(&q->lock, flags);
}
