orangefs: free superblock when mount fails

Otherwise lockdep says:

[ 1337.483798] ================================================
[ 1337.483999] [ BUG: lock held when returning to user space! ]
[ 1337.484252] 4.11.0-rc6 #19 Not tainted
[ 1337.484423] ------------------------------------------------
[ 1337.484626] mount/14766 is leaving the kernel with locks still held!
[ 1337.484841] 1 lock held by mount/14766:
[ 1337.485017]  #0:  (&type->s_umount_key#33/1){+.+.+.}, at: [<ffffffff8124171f>] sget_userns+0x2af/0x520

Caught by xfstests generic/413 which tried to mount with the unsupported
mount option dax.  Then xfstests generic/422 ran sync which deadlocks.
Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Acked-by: Mike Marshall <hubcap@omnibond.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/orangefs/devorangefs-req.c

@@ -208,14 +208,19 @@ static ssize_t orangefs_devreq_read(struct file *file,
 				continue;
 			/*
 			 * Skip ops whose filesystem we don't know about unless
-			 * it is being mounted.
+			 * it is being mounted or unmounted.  It is possible for
+			 * a filesystem we don't know about to be unmounted if
+			 * it fails to mount in the kernel after userspace has
+			 * been sent the mount request.
 			 */
 			/* XXX: is there a better way to detect this? */
 			} else if (ret == -1 &&
 				   !(op->upcall.type ==
 					ORANGEFS_VFS_OP_FS_MOUNT ||
 				     op->upcall.type ==
-					ORANGEFS_VFS_OP_GETATTR)) {
+					ORANGEFS_VFS_OP_GETATTR ||
+				     op->upcall.type ==
+					ORANGEFS_VFS_OP_FS_UMOUNT)) {
 				gossip_debug(GOSSIP_DEV_DEBUG,
 				    "orangefs: skipping op tag %llu %s\n",
 				    llu(op->tag), get_opname_string(op));

fs/orangefs/orangefs-kernel.h

@@ -249,6 +249,7 @@ struct orangefs_sb_info_s {
 	char devname[ORANGEFS_MAX_SERVER_ADDR_LEN];
 	struct super_block *sb;
 	int mount_pending;
+	int no_list;
 	struct list_head list;
 };
 

fs/orangefs/super.c

@@ -493,7 +493,7 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
 
 	if (ret) {
 		d = ERR_PTR(ret);
-		goto free_op;
+		goto free_sb_and_op;
 	}
 
 	/*
@@ -519,6 +519,9 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
 	spin_unlock(&orangefs_superblocks_lock);
 	op_release(new_op);
 
+	/* Must be removed from the list now. */
+	ORANGEFS_SB(sb)->no_list = 0;
+
 	if (orangefs_userspace_version >= 20906) {
 		new_op = op_alloc(ORANGEFS_VFS_OP_FEATURES);
 		if (!new_op)
@@ -533,6 +536,10 @@ struct dentry *orangefs_mount(struct file_system_type *fst,
 
 	return dget(sb->s_root);
 
+free_sb_and_op:
+	/* Will call orangefs_kill_sb with sb not in list. */
+	ORANGEFS_SB(sb)->no_list = 1;
+	deactivate_locked_super(sb);
 free_op:
 	gossip_err("orangefs_mount: mount request failed with %d\n", ret);
 	if (ret == -EINVAL) {
@@ -558,12 +565,14 @@ void orangefs_kill_sb(struct super_block *sb)
 	 */
 	 orangefs_unmount_sb(sb);
 
+	if (!ORANGEFS_SB(sb)->no_list) {
 		/* remove the sb from our list of orangefs specific sb's */
-
 		spin_lock(&orangefs_superblocks_lock);
-	__list_del_entry(&ORANGEFS_SB(sb)->list);	/* not list_del_init */
+		/* not list_del_init */
+		__list_del_entry(&ORANGEFS_SB(sb)->list);
 		ORANGEFS_SB(sb)->list.prev = NULL;
 		spin_unlock(&orangefs_superblocks_lock);
+	}
 
 	/*
 	 * make sure that ORANGEFS_DEV_REMOUNT_ALL loop that might've seen us