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.c b/fs/9p/v9fs.c
index 3c492011221c..38dc0e067599 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -237,6 +237,7 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
                 __putname(v9ses->uname);
                 return ERR_PTR(-ENOMEM);
         }
+        init_rwsem(&v9ses->rename_sem);
 
         rc = bdi_setup_and_register(&v9ses->bdi, "9p", BDI_CAP_MAP_COPY);
         if (rc) {