From 0410cd844ed0af3db3cb510d877d62c66d26e5cc Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Wed, 4 Oct 2023 17:53:15 +0100 Subject: mm: add folio_xor_flags_has_waiters() Optimise folio_end_read() by setting the uptodate bit at the same time we clear the unlock bit. This saves at least one memory barrier and one write-after-write hazard. Link: https://lkml.kernel.org/r/20231004165317.1061855-16-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Cc: Albert Ou Cc: Alexander Gordeev Cc: Andreas Dilger Cc: Christian Borntraeger Cc: Christophe Leroy Cc: Geert Uytterhoeven Cc: Heiko Carstens Cc: Ivan Kokshaysky Cc: Matt Turner Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Richard Henderson Cc: Sven Schnelle Cc: "Theodore Ts'o" Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Signed-off-by: Andrew Morton --- mm/filemap.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index 458377e9a184..e9c636f57777 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1497,7 +1497,7 @@ void folio_unlock(struct folio *folio) BUILD_BUG_ON(PG_waiters != 7); BUILD_BUG_ON(PG_locked > 7); VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); - if (xor_unlock_is_negative_byte(1 << PG_locked, folio_flags(folio, 0))) + if (folio_xor_flags_has_waiters(folio, 1 << PG_locked)) folio_wake_bit(folio, PG_locked); } EXPORT_SYMBOL(folio_unlock); @@ -1518,9 +1518,17 @@ EXPORT_SYMBOL(folio_unlock); */ void folio_end_read(struct folio *folio, bool success) { + unsigned long mask = 1 << PG_locked; + + /* Must be in bottom byte for x86 to work */ + BUILD_BUG_ON(PG_uptodate > 7); + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); + VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio); + if (likely(success)) - folio_mark_uptodate(folio); - folio_unlock(folio); + mask |= 1 << PG_uptodate; + if (folio_xor_flags_has_waiters(folio, mask)) + folio_wake_bit(folio, PG_locked); } EXPORT_SYMBOL(folio_end_read); -- cgit