The quilt patch titled
Subject: mm: add folio_xor_flags_has_waiters()
has been removed from the -mm tree. Its filename was
mm-add-folio_xor_flags_has_waiters.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: add folio_xor_flags_has_waiters()
Date: Wed, 4 Oct 2023 17:53:15 +0100
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@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Richard Henderson <richard.henderson@xxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page-flags.h | 19 +++++++++++++++++++
mm/filemap.c | 14 +++++++++++---
2 files changed, 30 insertions(+), 3 deletions(-)
--- a/include/linux/page-flags.h~mm-add-folio_xor_flags_has_waiters
+++ a/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.
*
--- a/mm/filemap.c~mm-add-folio_xor_flags_has_waiters
+++ a/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);
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
buffer-make-folio_create_empty_buffers-return-a-buffer_head.patch
mpage-convert-map_buffer_to_folio-to-folio_create_empty_buffers.patch
ext4-convert-to-folio_create_empty_buffers.patch
buffer-add-get_nth_bh.patch
gfs2-convert-inode-unstuffing-to-use-a-folio.patch
gfs2-convert-gfs2_getbuf-to-folios.patch
gfs2-convert-gfs2_getjdatabuf-to-use-a-folio.patch
gfs2-convert-gfs2_write_buf_to_page-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_freeze_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_grab_buffer-to-use-a-folio.patch
nilfs2-convert-nilfs_copy_page-to-nilfs_copy_folio.patch
nilfs2-convert-nilfs_mdt_forget_block-to-use-a-folio.patch
nilfs2-convert-nilfs_mdt_get_frozen_buffer-to-use-a-folio.patch
nilfs2-remove-nilfs_page_get_nth_block.patch
nilfs2-convert-nilfs_lookup_dirty_data_buffers-to-use-folio_create_empty_buffers.patch
ntfs-convert-ntfs_read_block-to-use-a-folio.patch
ntfs-convert-ntfs_writepage-to-use-a-folio.patch
ntfs-convert-ntfs_prepare_pages_for_non_resident_write-to-folios.patch
ntfs3-convert-ntfs_zero_range-to-use-a-folio.patch
ocfs2-convert-ocfs2_map_page_blocks-to-use-a-folio.patch
reiserfs-convert-writepage-to-use-a-folio.patch
ufs-add-ufs_get_locked_folio-and-ufs_put_locked_folio.patch
ufs-use-ufs_get_locked_folio-in-ufs_alloc_lastblock.patch
ufs-convert-ufs_change_blocknr-to-use-folios.patch
ufs-remove-ufs_get_locked_page.patch
buffer-remove-folio_create_empty_buffers.patch
