[PATCH] Btrfs: fix double initialization of the raid kobject

[PATCH] Btrfs: fix double initialization of the raid kobject

[Miao Xie]

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>
---
 fs/btrfs/extent-tree.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cd4d9ca..d667aad 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3464,8 +3464,10 @@ 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;
@@ -8423,9 +8425,8 @@ 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",
-					   get_raid_name(index));
+		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");
 			kobject_put(&space_info->kobj);
-- 
1.8.3.1

Re: [PATCH] Btrfs: fix double initialization of the raid kobject

[Miao Xie]

On tue, 17 Dec 2013 12:01:12 +0800, Miao Xie wrote:
> 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>

This bug was reported by Wang Shilong, so add

Reported-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>

Thanks
Miao

> ---
>  fs/btrfs/extent-tree.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index cd4d9ca..d667aad 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -3464,8 +3464,10 @@ 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;
> @@ -8423,9 +8425,8 @@ 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",
> -					   get_raid_name(index));
> +		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");
>  			kobject_put(&space_info->kobj);
>