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>

diff --git a/mm/filemap.c b/mm/filemap.c
index 523d9e15b3b0871ea912c53ff809f10a83d1abaf..b04ba896aac9fc9f82547c898bfc309434c83e74 100644 (file)
--- 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);
 }

diff --git a/mm/internal.h b/mm/internal.h
index ac4bbe2e2ca6a14542ff02c9a1caa4fcd3267827..2b79da9deb64acfa80f6dd87cb1cab47ca368e33 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -105,7 +105,7 @@ static inline void wake_throttle_isolated(pg_data_t *pgdat)
 
 vm_fault_t do_swap_page(struct vm_fault *vmf);
 void folio_rotate_reclaimable(struct folio *folio);
-void __folio_end_writeback(struct folio *folio);
+bool __folio_end_writeback(struct folio *folio);
 void deactivate_file_folio(struct folio *folio);
 void folio_activate(struct folio *folio);
 

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index a37e4c33d1ab739c980a423ec9a5d82649456f17..46f2f5d3d183b586e9936a92ed08ba08f6bf9755 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2940,10 +2940,11 @@ static void wb_inode_writeback_end(struct bdi_writeback *wb)
        spin_unlock_irqrestore(&wb->work_lock, flags);
 }
 
-void __folio_end_writeback(struct folio *folio)
+bool __folio_end_writeback(struct folio *folio)
 {
        long nr = folio_nr_pages(folio);
        struct address_space *mapping = folio_mapping(folio);
+       bool ret;
 
        folio_memcg_lock(folio);
        if (mapping && mapping_use_writeback_tags(mapping)) {
@@ -2952,7 +2953,7 @@ void __folio_end_writeback(struct folio *folio)
                unsigned long flags;
 
                xa_lock_irqsave(&mapping->i_pages, flags);
-               folio_test_clear_writeback(folio);
+               ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
                __xa_clear_mark(&mapping->i_pages, folio_index(folio),
                                        PAGECACHE_TAG_WRITEBACK);
                if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
@@ -2970,13 +2971,15 @@ void __folio_end_writeback(struct folio *folio)
 
                xa_unlock_irqrestore(&mapping->i_pages, flags);
        } else {
-               folio_test_clear_writeback(folio);
+               ret = folio_xor_flags_has_waiters(folio, 1 << PG_writeback);
        }
 
        lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
        zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
        node_stat_mod_folio(folio, NR_WRITTEN, nr);
        folio_memcg_unlock(folio);
+
+       return ret;
 }
 
 bool __folio_start_writeback(struct folio *folio, bool keep_write)