| Message ID | 20201029190748.u5zrnk6rjtc4p43v@linux-p48b (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] fs/dcache: optimize start_dir_add() | expand |
diff --git a/fs/dcache.c b/fs/dcache.c index ea0485861d93..9177f0d08a5a 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2504,8 +2504,8 @@ static inline unsigned start_dir_add(struct inode *dir) { 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) && cmpxchg_acquire(&dir->i_dir_seq, n, n + 1) == n) return n; cpu_relax(); }
Considering both end_dir_add() and d_alloc_parallel(), the dir->i_dir_seq wants acquire/release semantics, therefore micro-optimize for ll/sc archs. Also add READ_ONCE around the variable mostly for documentation purposes - either the successful cmpxchg or the pause will avoid the tearing). Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- fs/dcache.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) -- 2.26.2