From: Dave Chinner <dchinner@xxxxxxxxxx>
When lockdep is enabled, it changes the type of the inode i_rwsem
semaphore before unlocking a newly instantiated inode. THere is the
possibility that there is already a waiter on that inode lock by the
time we unlock the new inode, so having lockdep re-initialise the
lock is a vector for trouble.
Avoid this whole situation by setting up the i_rwsem lockdep class
at the same time we set up the XFS inode i_ilock classes and so the
VFS doesn't have to change the lock class itself when it is
potentially unsafe.
Signed-Off-By: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_iops.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 29484091c0d2..3020c57fc125 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1258,6 +1258,14 @@ xfs_setup_inode(
xfs_diflags_to_iflags(inode, ip);
if (S_ISDIR(inode->i_mode)) {
+ /*
+ * We set the i_rwsem class here to avoid potential races with
+ * lockdep_annotate_inode_mutex_key() reinitialising the lock
+ * after a filehandle lookup has already found the inode in
+ * cache before it has been unlocked via unlock_new_inode().
+ */
+ lockdep_set_class(&inode->i_rwsem,
+ &inode->i_sb->s_type->i_mutex_dir_key);
lockdep_set_class(&ip->i_lock.mr_lock, &xfs_dir_ilock_class);
ip->d_ops = ip->i_mount->m_dir_inode_ops;
} else {
--
2.17.0
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