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, 10 insertions, 3 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 39352ef954dc..75c261fdc7b4 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -948,6 +948,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 
         sb = dir->i_sb;
         v9ses = v9fs_inode2v9ses(dir);
+        /* We can walk d_parent because we hold the dir->i_mutex */
         dfid = v9fs_fid_lookup(dentry->d_parent);
         if (IS_ERR(dfid))
                 return ERR_CAST(dfid);
@@ -1055,27 +1056,33 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                 goto clunk_olddir;
         }
 
+        down_write(&v9ses->rename_sem);
         if (v9fs_proto_dotl(v9ses)) {
                 retval = p9_client_rename(oldfid, newdirfid,
                                         (char *) new_dentry->d_name.name);
                 if (retval != -ENOSYS)
                         goto clunk_newdir;
         }
+        if (old_dentry->d_parent != new_dentry->d_parent) {
+                /*
+                 * 9P .u can only handle file rename in the same directory
+                 */
 
-        /* 9P can only handle file rename in the same directory */
-        if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {
                 P9_DPRINTK(P9_DEBUG_ERROR,
                                 "old dir and new dir are different\n");
                 retval = -EXDEV;
                 goto clunk_newdir;
         }
-
         v9fs_blank_wstat(&wstat);
         wstat.muid = v9ses->uname;
         wstat.name = (char *) new_dentry->d_name.name;
         retval = p9_client_wstat(oldfid, &wstat);
 
 clunk_newdir:
+        if (!retval)
+                /* successful rename */
+                d_move(old_dentry, new_dentry);
+        up_write(&v9ses->rename_sem);
         p9_client_clunk(newdirfid);
 
 clunk_olddir: