NFS: handle inode==NULL in __put_nfs_open_context

inode may be NULL when put_nfs_open_context is called from nfs_atomic_lookup
before d_add_unique(dentry, inode)
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/inode.c

@@ -654,11 +654,14 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync)
 {
 	struct inode *inode = ctx->path.dentry->d_inode;
 
+	if (inode) {
 		if (!atomic_dec_and_lock(&ctx->lock_context.count, &inode->i_lock))
 			return;
 		list_del(&ctx->list);
 		spin_unlock(&inode->i_lock);
 		NFS_PROTO(inode)->close_context(ctx, is_sync);
+	} else if (!atomic_dec_and_test(&ctx->lock_context.count))
+		return;
 	if (ctx->cred != NULL)
 		put_rpccred(ctx->cred);
 	path_put(&ctx->path);