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().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index ddcced4638b53133c0eee1fa136717e2061e5cc0..56bfba546be7ba2d11d4fd4186a2e25c84fe17be 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1177,13 +1177,6 @@ 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():
  */
@@ -1620,13 +1613,11 @@ 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 ccb08dd9b5ec7b47a827ead5327941eceffca8f6..30cf724ddbce3399999d6a9e9816fa133e9c5c4b 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 410b53e888e3b649986d7b4c9c23695e3464bace..c52514fe1d2355a30d2076965ba6b1be31856816 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)