[PATCH v2 2/2] fs: dcache: Use READ_ONCE when accessing i_dir_seq

[Will Deacon]

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 <pet...@infradead.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
---
 fs/dcache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index b243deec298c..5716ab04e1db 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2502,7 +2502,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
        }
 
        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;
-- 
2.1.4