fs/9p: Prevent parallel rename when doing fid_lookup

During fid lookup we need to make sure that the dentry->d_parent doesn't
change so that we can safely walk the parent dentries. To ensure that
we need to prevent cross directory rename during fid_lookup. Add a
per superblock rename_sem rw_semaphore to prevent parallel fid lookup and
rename.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index bec4d0bcb458..4c963c9fc41f 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -104,6 +104,7 @@ struct v9fs_session_info {
         struct p9_client *clnt; /* 9p client */
         struct list_head slist; /* list of sessions registered with v9fs */
         struct backing_dev_info bdi;
+        struct rw_semaphore rename_sem;
 };
 
 struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,