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| author | Uros Bizjak <ubizjak@gmail.com> | 2025-08-11 14:52:38 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-08-25 14:09:00 +0200 |
| commit | 14498ca7e0f18cd73ab0010cbfbf9413a9f0a96f (patch) | |
| tree | 8d3c9a3a76bef235d95bb0197c22f21c2e06bcef | |
| parent | 278033a225e13ec21900f0a92b8351658f5377f2 (diff) | |
| download | tip-14498ca7e0f18cd73ab0010cbfbf9413a9f0a96f.tar.gz | |
fs: Use try_cmpxchg() in start_dir_add()
Use try_cmpxchg() instead of cmpxchg(*ptr, old, new) == old.
The x86 CMPXCHG instruction returns success in the ZF flag,
so this change saves a compare after CMPXCHG (and related
move instruction in front of CMPXCHG).
Note that the value from *ptr should be read using READ_ONCE() to
prevent the compiler from merging, refetching or reordering the read.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/20250811125308.616717-1-ubizjak@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
| -rw-r--r-- | fs/dcache.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 60046ae23d5148..336bdb4c4b1f4e 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2509,8 +2509,8 @@ static inline unsigned start_dir_add(struct inode *dir) { preempt_disable_nested(); for (;;) { - unsigned n = dir->i_dir_seq; - if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n) + unsigned n = READ_ONCE(dir->i_dir_seq); + if (!(n & 1) && try_cmpxchg(&dir->i_dir_seq, &n, n + 1)) return n; cpu_relax(); } |