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Subject[PATCH 4.9 143/329] fs: dcache: Use READ_ONCE when accessing i_dir_seq
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@arm.com>

[ 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>
---
fs/dcache.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2502,7 +2502,7 @@ 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;

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