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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>
This commit is contained in:
Will Deacon 2018-02-19 14:55:55 +00:00 committed by Al Viro
parent 015555fd4d
commit 8cc07c808c
1 changed files with 1 additions and 1 deletions
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2
fs/dcache.c
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@ -2507,7 +2507,7 @@ 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;