Re: [PATCH 1/2] Btrfs: fix OOPS of empty filesystem after balance

[liubo <liubo2009@cn.fujitsu.com>]

On 03/30/2011 07:58 PM, Arne Jansen wrote:
> Am 10.03.2011 13:28, schrieb Chris Mason:
>> Excerpts from liubo's message of 2011-03-10 03:50:27 -0500:
>>> On 03/07/2011 10:13 AM, liubo wrote:
>>>> btrfs will remove unused block groups after balance.
>>>> When a empty filesystem is balanced, the block group with tag "DATA" may be
>>>> dropped, and after umount and mount again, it will not find "DATA" space_info
>>>> and lead to OOPS.
>>>> So we initial the necessary space_infos(DATA, SYSTEM, METADATA) to avoid OOPS.
>>>>
> 
> this patch breaks mixed block groups. If the space_infos get added
> upfront, later on all mixed block groups will be added to the data
> space_info, leaving the metadata space_info completely empty.
> No mixed space_info will ever get created.

Hi, Arne,

Sorry for the late reply.

> As a fix it might be enough to call btrfs_init_space_info after
> btrfs_read_block_groups, not before, but I haven't tested it.
> 

Seems impossible, the original bug just occurs in btrfs_read_block_groups()...

> This was the cause of the BUG reported by Sergei Trofimovich in the
> thread "v2.6.38-6555-ga44f99c: null pointer dereference on -ENOSPC".
> 

Thanks for pointing this out.
Anyway, will dig it more.

thanks,
liubo

> -Arne
> 
>>> Hi, Chirs,
>>>
>>> These two fixes are for critical problems(one OOPS and one memory leak), so would
>>> you please take some time to review them and check if they are ready for the next
>>> git pull? 
>>>
>>> Seems that you have been a lot busy these days. ;)
>> Hi Liubo,
>>
>> I'm looking at both of these.  There are no more rc's for 2.6.38, only
>> the final release, so the bar is very high for a commit that goes in.
>>
>> -chris
>>
>>> thanks,
>>> liubo
>>>
>>>> Reported-by: Daniel J Blueman <daniel.blueman@gmail.com>
>>>> Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
>>>> ---
>>>>  fs/btrfs/ctree.h       |    1 +
>>>>  fs/btrfs/disk-io.c     |    6 ++++++
>>>>  fs/btrfs/extent-tree.c |   23 +++++++++++++++++++++++
>>>>  3 files changed, 30 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
>>>> index 28188a7..49c50e5 100644
>>>> --- a/fs/btrfs/ctree.h
>>>> +++ b/fs/btrfs/ctree.h
>>>> @@ -2221,6 +2221,7 @@ int btrfs_error_discard_extent(struct btrfs_root *root, u64 bytenr,
>>>>                     u64 num_bytes);
>>>>  int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans,
>>>>                  struct btrfs_root *root, u64 type);
>>>> +int btrfs_init_space_info(struct btrfs_fs_info *fs_info);
>>>>  
>>>>  /* ctree.c */
>>>>  int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
>>>> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
>>>> index 3e1ea3e..8bcdc62 100644
>>>> --- a/fs/btrfs/disk-io.c
>>>> +++ b/fs/btrfs/disk-io.c
>>>> @@ -1967,6 +1967,12 @@ struct btrfs_root *open_ctree(struct super_block *sb,
>>>>      fs_info->metadata_alloc_profile = (u64)-1;
>>>>      fs_info->system_alloc_profile = fs_info->metadata_alloc_profile;
>>>>  
>>>> +    ret = btrfs_init_space_info(fs_info);
>>>> +    if (ret) {
>>>> +        printk(KERN_ERR "Failed to initial space info: %d\n", ret);
>>>> +        goto fail_block_groups;
>>>> +    }
>>>> +
>>>>      ret = btrfs_read_block_groups(extent_root);
>>>>      if (ret) {
>>>>          printk(KERN_ERR "Failed to read block groups: %d\n", ret);
>>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>>>> index 100e409..08525ee 100644
>>>> --- a/fs/btrfs/extent-tree.c
>>>> +++ b/fs/btrfs/extent-tree.c
>>>> @@ -8714,6 +8714,29 @@ out:
>>>>      return ret;
>>>>  }
>>>>  
>>>> +int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
>>>> +{
>>>> +    struct btrfs_space_info *space_info;
>>>> +    int ret;
>>>> +
>>>> +    ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM, 0, 0,
>>>> +                                 &space_info);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA, 0, 0,
>>>> +                                 &space_info);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    ret = update_space_info(fs_info, BTRFS_BLOCK_GROUP_DATA, 0, 0,
>>>> +                                 &space_info);
>>>> +    if (ret)
>>>> +        return ret;
>>>> +
>>>> +    return ret;
>>>> +}
>>>> +
>>>>  int btrfs_error_unpin_extent_range(struct btrfs_root *root, u64 start, u64 end)
>>>>  {
>>>>      return unpin_extent_range(root, start, end);
>