Re: [PATCH] Btrfs: fix regression of btrfs device replace

[Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>]

Hi Liu,

(2014/08/12 6:41), Chris Murphy wrote:
>
> On Jul 29, 2014, at 5:09 AM, Liu Bo <bo.li.liu@oracle.com> wrote:
>
>> Commit 49c6f736f34f901117c20960ebd7d5e60f12fcac(
>> btrfs: dev replace should replace the sysfs entry) added the missing sysfs entry
>> in the process of device replace, but didn't take missing devices into account,
>> so now we have
>>
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000088
>> IP: [<ffffffffa0268551>] btrfs_kobj_rm_device+0x21/0x40 [btrfs]
>> ...
>>
>> To reproduce it,
>> 1. mkfs.btrfs -f disk1 disk2
>> 2. mkfs.ext4 disk1
>> 3. mount disk2 /mnt -odegraded
>> 4. btrfs replace start -B 1 disk3 /mnt
>> --------------------------
>>
>> This fixes the problem.
>>
>> Reported-by: Chris Murphy <lists@colorremedies.com>
>> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
>> ---
>> fs/btrfs/sysfs.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
>> index 7869936..12e5355 100644
>> --- a/fs/btrfs/sysfs.c
>> +++ b/fs/btrfs/sysfs.c
>> @@ -614,7 +614,7 @@ int btrfs_kobj_rm_device(struct btrfs_fs_info *fs_info,
>> 	if (!fs_info->device_dir_kobj)
>> 		return -EINVAL;
>>
>> -	if (one_device) {
>> +	if (one_device && one_device->bdev) {
>> 		disk = one_device->bdev->bd_part;
>> 		disk_kobj = &part_to_dev(disk)->kobj;
>>
>
>
> Applied to 3.16.0 and tested, problem is fixed.
>
>
> Chris Murphy

Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Tested-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>

I confirmed both

  - This problem happens with 3.16, and
  - This problem doesn't happen with 3.16 + your patch.

Thanks,
Satoru

>
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