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| author |  Uros Bizjak <ubizjak@gmail.com>
| 2022-11-02 08:11:47 +0100 |
|---|---|---|
| committer |  Andrew Morton <akpm@linux-foundation.org>
| 2023-02-02 22:50:07 -0800 |
| commit | 3ee2a3e7c1ca3b263c41cff81619ab1d200fadfb (patch) | |
| tree | 313524c855b5461998f72558e738053259a2c28a | |
| parent | fs: hfsplus: initialize fsdata in hfsplus_file_truncate() (diff) | |
| download | linux-3ee2a3e7c1ca3b263c41cff81619ab1d200fadfb.tar.gz linux-3ee2a3e7c1ca3b263c41cff81619ab1d200fadfb.tar.bz2 linux-3ee2a3e7c1ca3b263c41cff81619ab1d200fadfb.zip | |
fs/ext4: use try_cmpxchg in ext4_update_bh_state
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
ext4_update_bh_state. x86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related move instruction
in front of cmpxchg).
Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails. There is no need to re-read the value in the loop.
No functional change intended.
Link: https://lkml.kernel.org/r/20221102071147.6642-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | fs/ext4/inode.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 9d9f414f99fe..dc8da7bbc240 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -786,11 +786,10 @@ static void ext4_update_bh_state(struct buffer_head *bh, unsigned long flags) * once we get rid of using bh as a container for mapping information * to pass to / from get_block functions, this can go away. */ + old_state = READ_ONCE(bh->b_state); do { - old_state = READ_ONCE(bh->b_state); new_state = (old_state & ~EXT4_MAP_FLAGS) | flags; - } while (unlikely( - cmpxchg(&bh->b_state, old_state, new_state) != old_state)); + } while (unlikely(!try_cmpxchg(&bh->b_state, &old_state, new_state))); } static int _ext4_get_block(struct inode *inode, sector_t iblock, |