The patch titled
Subject: iomap: hold state_lock over call to ifs_set_range_uptodate()
has been added to the -mm mm-unstable branch. Its filename is
iomap-hold-state_lock-over-call-to-ifs_set_range_uptodate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/iomap-hold-state_lock-over-call-to-ifs_set_range_uptodate.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: iomap: hold state_lock over call to ifs_set_range_uptodate()
Date: Wed, 4 Oct 2023 17:53:01 +0100
Patch series "Add folio_end_read", v2.
The core of this patchset is the new folio_end_read() call which
filesystems can use when finishing a page cache read instead of separate
calls to mark the folio uptodate and unlock it. As an illustration of its
use, I converted ext4, iomap & mpage; more can be converted.
I think that's useful by itself, but the interesting optimisation is that
we can implement that with a single XOR instruction that sets the uptodate
bit, clears the lock bit, tests the waiter bit and provides a write memory
barrier. That removes one memory barrier and one atomic instruction from
each page read, which seems worth doing. That's in patch 15.
The last two patches could be a separate series, but basically we can do
the same thing with the writeback flag that we do with the unlock flag;
clear it and test the waiters bit at the same time.
This patch (of 17):
This is really preparation for the next patch, but it lets us call
folio_mark_uptodate() in just one place instead of two.
Link: https://lkml.kernel.org/r/20231004165317.1061855-1-willy@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20231004165317.1061855-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx>
Cc: Richard Henderson <richard.henderson@xxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/iomap/buffered-io.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
--- a/fs/iomap/buffered-io.c~iomap-hold-state_lock-over-call-to-ifs_set_range_uptodate
+++ a/fs/iomap/buffered-io.c
@@ -57,30 +57,32 @@ static inline bool ifs_block_is_uptodate
return test_bit(block, ifs->state);
}
-static void ifs_set_range_uptodate(struct folio *folio,
+static bool ifs_set_range_uptodate(struct folio *folio,
struct iomap_folio_state *ifs, size_t off, size_t len)
{
struct inode *inode = folio->mapping->host;
unsigned int first_blk = off >> inode->i_blkbits;
unsigned int last_blk = (off + len - 1) >> inode->i_blkbits;
unsigned int nr_blks = last_blk - first_blk + 1;
- unsigned long flags;
- spin_lock_irqsave(&ifs->state_lock, flags);
bitmap_set(ifs->state, first_blk, nr_blks);
- if (ifs_is_fully_uptodate(folio, ifs))
- folio_mark_uptodate(folio);
- spin_unlock_irqrestore(&ifs->state_lock, flags);
+ return ifs_is_fully_uptodate(folio, ifs);
}
static void iomap_set_range_uptodate(struct folio *folio, size_t off,
size_t len)
{
struct iomap_folio_state *ifs = folio->private;
+ unsigned long flags;
+ bool uptodate = true;
+
+ if (ifs) {
+ spin_lock_irqsave(&ifs->state_lock, flags);
+ uptodate = ifs_set_range_uptodate(folio, ifs, off, len);
+ spin_unlock_irqrestore(&ifs->state_lock, flags);
+ }
- if (ifs)
- ifs_set_range_uptodate(folio, ifs, off, len);
- else
+ if (uptodate)
folio_mark_uptodate(folio);
}
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-make-lock_folio_maybe_drop_mmap-vma-lock-aware.patch
mm-call-wp_page_copy-under-the-vma-lock.patch
mm-handle-shared-faults-under-the-vma-lock.patch
mm-handle-cow-faults-under-the-vma-lock.patch
mm-handle-read-faults-under-the-vma-lock.patch
mm-handle-write-faults-to-ro-pages-under-the-vma-lock.patch
iomap-hold-state_lock-over-call-to-ifs_set_range_uptodate.patch
iomap-protect-read_bytes_pending-with-the-state_lock.patch
mm-add-folio_end_read.patch
ext4-use-folio_end_read.patch
buffer-use-folio_end_read.patch
iomap-use-folio_end_read.patch
bitops-add-xor_unlock_is_negative_byte.patch
alpha-implement-xor_unlock_is_negative_byte.patch
m68k-implement-xor_unlock_is_negative_byte.patch
mips-implement-xor_unlock_is_negative_byte.patch
powerpc-implement-arch_xor_unlock_is_negative_byte-on-32-bit.patch
riscv-implement-xor_unlock_is_negative_byte.patch
s390-implement-arch_xor_unlock_is_negative_byte.patch
mm-delete-checks-for-xor_unlock_is_negative_byte.patch
mm-add-folio_xor_flags_has_waiters.patch
mm-make-__end_folio_writeback-return-void.patch
mm-use-folio_xor_flags_has_waiters-in-folio_end_writeback.patch
