fs/9p: Fix race in initializing writeback fid

When two process open the same file we can end up with both of them
allocating the writeback_fid. Add a new mutex which can be used
for synchronizing v9fs_inode member values.

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, 3 insertions, 0 deletions

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 67c138e94feb..327c578c7ba6 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -245,6 +245,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
         v9fs_set_create_acl(dentry, dacl, pacl);
 
         v9inode = V9FS_I(inode);
+        mutex_lock(&v9inode->v_mutex);
         if (v9ses->cache && !v9inode->writeback_fid) {
                 /*
                  * clone a fid and add it to writeback_fid
@@ -256,10 +257,12 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
                 inode_fid = v9fs_writeback_fid(dentry);
                 if (IS_ERR(inode_fid)) {
                         err = PTR_ERR(inode_fid);
+                        mutex_unlock(&v9inode->v_mutex);
                         goto error;
                 }
                 v9inode->writeback_fid = (void *) inode_fid;
         }
+        mutex_unlock(&v9inode->v_mutex);
         /* Since we are opening a file, assign the open fid to the file */
         filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
         if (IS_ERR(filp)) {