[PATCH 3.16 104/157] ceph: ensure d_name stability in ceph_dentry_hash()

[Ben Hutchings]

3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Jeff Layton <jlayton@xxxxxxxxxx>

commit 76a495d666e5043ffc315695f8241f5e94a98849 upstream.

Take the d_lock here to ensure that d_name doesn't change.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/ceph/dir.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1327,6 +1327,7 @@ void ceph_dentry_lru_del(struct dentry *
 unsigned ceph_dentry_hash(struct inode *dir, struct dentry *dn)
 {
 	struct ceph_inode_info *dci = ceph_inode(dir);
+	unsigned hash;
 
 	switch (dci->i_dir_layout.dl_dir_hash) {
 	case 0:	/* for backward compat */
@@ -1334,8 +1335,11 @@ unsigned ceph_dentry_hash(struct inode *
 		return dn->d_name.hash;
 
 	default:
-		return ceph_str_hash(dci->i_dir_layout.dl_dir_hash,
+		spin_lock(&dn->d_lock);
+		hash = ceph_str_hash(dci->i_dir_layout.dl_dir_hash,
 				     dn->d_name.name, dn->d_name.len);
+		spin_unlock(&dn->d_lock);
+		return hash;
 	}
 }