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, 4 insertions, 0 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 8a2c232f708a..c6cef2495f00 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -221,6 +221,7 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 #endif
         v9inode->writeback_fid = NULL;
         v9inode->cache_validity = 0;
+        mutex_init(&v9inode->v_mutex);
         return &v9inode->vfs_inode;
 }
 
@@ -650,6 +651,7 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
         /* if we are opening a file, assign the open fid to the file */
         if (nd && nd->flags & LOOKUP_OPEN) {
                 v9inode = V9FS_I(dentry->d_inode);
+                mutex_lock(&v9inode->v_mutex);
                 if (v9ses->cache && !v9inode->writeback_fid) {
                         /*
                          * clone a fid and add it to writeback_fid
@@ -661,10 +663,12 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
                         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);
                 filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
                 if (IS_ERR(filp)) {
                         err = PTR_ERR(filp);