Commit 527ed41f authored Feb 19, 2018 by Will Deacon Committed by Greg Kroah-Hartman May 30, 2018

fs: dcache: Use READ_ONCE when accessing i_dir_seq



[ Upstream commit 8cc07c808c9d595e81cbe5aad419b7769eb2e5c9 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bcefedb8

fs/dcache.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;