fs: dcache: Use READ_ONCE when accessing i_dir_seq

i_dir_seq is subject to concurrent modification by a cmpxchg or
store-release operation, so ensure that the relaxed access in
d_alloc_parallel uses READ_ONCE.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index bde3b6662601..8945e6cabd93 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2507,7 +2507,7 @@ retry:
         }
 
         hlist_bl_lock(b);
-        if (unlikely(parent->d_inode->i_dir_seq != seq)) {
+        if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
                 hlist_bl_unlock(b);
                 rcu_read_unlock();
                 goto retry;