Commit 536cd964 authored Dec 17, 2013 by Miao Xie Committed by Chris Mason Jan 28, 2014

Btrfs: fix double initialization of the raid kobject



We met the following oops when doing space balance:
 kobject (ffff88081b590278): tried to init an initialized object, something is seriously wrong.
 ...
 Call Trace:
  [<ffffffff81937262>] dump_stack+0x49/0x5f
  [<ffffffff8137d259>] kobject_init+0x89/0xa0
  [<ffffffff8137d36a>] kobject_init_and_add+0x2a/0x70
  [<ffffffffa009bd79>] ? clear_extent_bit+0x199/0x470 [btrfs]
  [<ffffffffa005e82c>] __link_block_group+0xfc/0x120 [btrfs]
  [<ffffffffa006b9db>] btrfs_make_block_group+0x24b/0x370 [btrfs]
  [<ffffffffa00a899b>] __btrfs_alloc_chunk+0x54b/0x7e0 [btrfs]
  [<ffffffffa00a8c6f>] btrfs_alloc_chunk+0x3f/0x50 [btrfs]
  [<ffffffffa0060123>] do_chunk_alloc+0x363/0x440 [btrfs]
  [<ffffffffa00633d4>] btrfs_check_data_free_space+0x104/0x310 [btrfs]
  [<ffffffffa0069f4d>] btrfs_write_dirty_block_groups+0x48d/0x600 [btrfs]
  [<ffffffffa007aad4>] commit_cowonly_roots+0x184/0x250 [btrfs]
  ...

Steps to reproduce:
 # mkfs.btrfs -f <dev>
 # mount -o nospace_cache <dev> <mnt>
 # btrfs balance start <mnt>
 # dd if=/dev/zero of=<mnt>/tmpfile bs=1M count=1

The reason of this problem is that we initialized the raid kobject when we added
a block group into a empty raid list. As we know, when we mounted a btrfs filesystem,
the raid list was empty, we would initialize the raid kobject when we added the first
block group. But if there was not data stored in the block group, the block group
would be freed when doing balance, and the raid list would be empty. And then if we
allocated a new block group and added it into the raid list, we would initialize
the raid kobject again, the oops happened.

Fix this problem by initializing the raid kobject just when mounting the fs.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reported-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 180589ef

fs/btrfs/extent-tree.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -3463,8 +3463,10 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
		return ret;
		}

		for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
		for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
		INIT_LIST_HEAD(&found->block_groups[i]);
		kobject_init(&found->block_group_kobjs[i], &btrfs_raid_ktype);
		}
		init_rwsem(&found->groups_sem);
		spin_lock_init(&found->lock);
		found->flags = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
		@@ -8422,8 +8424,7 @@ static void __link_block_group(struct btrfs_space_info *space_info,
		int ret;

		kobject_get(&space_info->kobj); /* put in release */
		ret = kobject_init_and_add(kobj, &btrfs_raid_ktype,
		&space_info->kobj, "%s",
		ret = kobject_add(kobj, &space_info->kobj, "%s",
		get_raid_name(index));
		if (ret) {
		pr_warn("btrfs: failed to add kobject for block cache. ignoring.\n");