mm: use folio_xor_flags_has_waiters() in folio_end_writeback()

Match how folio_unlock() works by combining the test for PG_waiters with
the clearing of PG_writeback.  This should have a small performance win,
and removes the last user of folio_wake().

Link: https://lkml.kernel.org/r/20231004165317.1061855-18-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 3 insertions, 12 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 523d9e15b3b0..b04ba896aac9 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1175,13 +1175,6 @@ static void folio_wake_bit(struct folio *folio, int bit_nr)
 	spin_unlock_irqrestore(&q->lock, flags);
 }
 
-static void folio_wake(struct folio *folio, int bit)
-{
-	if (!folio_test_waiters(folio))
-		return;
-	folio_wake_bit(folio, bit);
-}
-
 /*
  * A choice of three behaviors for folio_wait_bit_common():
  */
@@ -1618,13 +1611,11 @@ void folio_end_writeback(struct folio *folio)
 	 * Writeback does not hold a folio reference of its own, relying
 	 * on truncation to wait for the clearing of PG_writeback.
 	 * But here we must make sure that the folio is not freed and
-	 * reused before the folio_wake().
+	 * reused before the folio_wake_bit().
 	 */
 	folio_get(folio);
-	__folio_end_writeback(folio);
-
-	smp_mb__after_atomic();
-	folio_wake(folio, PG_writeback);
+	if (__folio_end_writeback(folio))
+		folio_wake_bit(folio, PG_writeback);
 	acct_reclaim_writeback(folio);
 	folio_put(folio);
 }