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    Subject[PATCH 4.4 08/22] ceph: fix improper use of smp_mb__before_atomic()
    Date
    [ 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 8c8cb8fe3d32f..5d05c77c158d4 100644
    --- a/fs/ceph/super.h
    +++ b/fs/ceph/super.h
    @@ -474,7 +474,12 @@ 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


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