[PATCH AUTOSEL 4.9 11/30] ceph: fix improper use of smp_mb__before_atomic()

Sasha Levin
2019-07-26T13:44:54Z

From: Andrea Parri <andrea.parri@amarulasolutions.com>

[ Upstream commit 749607731e26dfb2558118038c40e9c0c80d23b5 ]

This barrier only applies to the read-modify-write operations; in
particular, it does not apply to the atomic64_set() primitive.

Replace the barrier with an smp_mb().

Fixes: fdd4e15838e59 ("ceph: rework dcache readdir")
Reported-by: "Paul E. McKenney" <paulmck@linux.ibm.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ceph/super.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 622d5dd9f616..9bd0d928057b 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -476,7 +476,12 @@ static inline void __ceph_dir_set_complete(struct ceph_inode_info *ci,
long long release_count,
long long ordered_count)
{
- smp_mb__before_atomic();
+ /*
+ * Makes sure operations that setup readdir cache (update page
+ * cache and i_size) are strongly ordered w.r.t. the following
+ * atomic64_set() operations.
+ */
+ smp_mb();
atomic64_set(&ci->i_complete_seq[0], release_count);
atomic64_set(&ci->i_complete_seq[1], ordered_count);
}
--
2.20.1