Re: btrfs regression since 4.X kernel NULL pointer dereference

[Stefan Priebe <s.priebe@profihost.ag>]

Am 01.09.2015 um 02:06 schrieb Chris Mason:
> On Mon, Aug 31, 2015 at 07:32:09PM +0200, Stefan Priebe - Profihost AG wrote:
>>> Am 25.08.2015 um 15:51 schrieb Chris Mason <clm@fb.com>:
>>>
>>>> On Tue, Aug 25, 2015 at 11:00:30AM +0200, Christoph Hellwig wrote:
>>>> I think this is btrfs using a struct block_device that doesn't have
>>>> a valid queue pointer in it's gendisk for ->s_bdev.  And there are
>>>> some fishy looking ->s_bdev assignments in the code which I suspect
>>>> are related to it:
>>>>
>>>> fs/btrfs/dev-replace.c: if (fs_info->sb->s_bdev == src_device->bdev)
>>>> fs/btrfs/dev-replace.c:         fs_info->sb->s_bdev = tgt_device->bdev;
>>>> fs/btrfs/volumes.c:     if (device->bdev == root->fs_info->sb->s_bdev)
>>>> fs/btrfs/volumes.c:             root->fs_info->sb->s_bdev = next_device->bdev;
>>>> fs/btrfs/volumes.c:     if (tgtdev->bdev == fs_info->sb->s_bdev)
>>>> fs/btrfs/volumes.c:             fs_info->sb->s_bdev = next_device->bdev;
>>>
>>> We've had trouble with this in the past, I'll take a look.
>>
>> Any news?
>
> Haven't been able to reproduce yet, I'll try again in the morning.

Thanks. We're using schroot like the user in this bugreport:
https://bugzilla.kernel.org/show_bug.cgi?id=100911

But he also claims he found another way to reproduce using vfcgbackup 
(last comment).

Stefan

>
> -chris
>