cifs: have cifsFileInfo hold an extra inode reference

It's possible that this struct will outlive the filp to which it is
attached. If it does and it needs to do some work on the inode, then
it'll need a reference.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

fs/cifs/cifsglob.h

@@ -365,8 +365,10 @@ static inline void cifsFileInfo_get(struct cifsFileInfo *cifs_file)
 /* Release a reference on the file private data */
 static inline void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
 {
-	if (atomic_dec_and_test(&cifs_file->count))
+	if (atomic_dec_and_test(&cifs_file->count)) {
+		iput(cifs_file->pInode);
 		kfree(cifs_file);
+	}
 }
 
 /*

fs/cifs/dir.c

@@ -147,7 +147,7 @@ cifs_fill_fileinfo(struct inode *newinode, __u16 fileHandle,
 
 	pCifsFile->netfid = fileHandle;
 	pCifsFile->pid = current->tgid;
-	pCifsFile->pInode = newinode;
+	pCifsFile->pInode = igrab(newinode);
 	pCifsFile->invalidHandle = false;
 	pCifsFile->closePend = false;
 	mutex_init(&pCifsFile->fh_mutex);

fs/cifs/file.c

@@ -50,7 +50,7 @@ static inline struct cifsFileInfo *cifs_init_private(
 	mutex_init(&private_data->lock_mutex);
 	INIT_LIST_HEAD(&private_data->llist);
 	private_data->pfile = file; /* needed for writepage */
-	private_data->pInode = inode;
+	private_data->pInode = igrab(inode);
 	private_data->invalidHandle = false;
 	private_data->closePend = false;
 	/* Initialize reference count to one.  The private data is