diff options
author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2023-10-04 19:53:15 +0300 |
---|---|---|
committer | Andrew Morton <akpm@linux-foundation.org> | 2023-10-19 00:34:17 +0300 |
commit | 0410cd844ed0af3db3cb510d877d62c66d26e5cc (patch) | |
tree | d05e676a83fda128a26a87500f32b14adda6fdd9 | |
parent | f12fb73b74fd23ca33e3f95fb996f295eeae1da7 (diff) | |
download | linux-0410cd844ed0af3db3cb510d877d62c66d26e5cc.tar.xz |
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) <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>
-rw-r--r-- | include/linux/page-flags.h | 19 | ||||
-rw-r--r-- | mm/filemap.c | 14 |
2 files changed, 30 insertions, 3 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 5c02720c53a5..a88e64acebfe 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -693,6 +693,25 @@ TESTPAGEFLAG_FALSE(Ksm, ksm) u64 stable_page_flags(struct page *page); /** + * folio_xor_flags_has_waiters - Change some folio flags. + * @folio: The folio. + * @mask: Bits set in this word will be changed. + * + * This must only be used for flags which are changed with the folio + * lock held. For example, it is unsafe to use for PG_dirty as that + * can be set without the folio lock held. It can also only be used + * on flags which are in the range 0-6 as some of the implementations + * only affect those bits. + * + * Return: Whether there are tasks waiting on the folio. + */ +static inline bool folio_xor_flags_has_waiters(struct folio *folio, + unsigned long mask) +{ + return xor_unlock_is_negative_byte(mask, folio_flags(folio, 0)); +} + +/** * folio_test_uptodate - Is this folio up to date? * @folio: The folio. * 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); |