Re: __link_block_group uses GFP_KERNEL

[Denis Kirjanov]

On 3/25/17, Jeff Mahoney <jeffm@xxxxxxxx> wrote:
> On 3/24/17 5:02 AM, Denis Kirjanov wrote:
>> Hi guys,
>>
>> Looks like that current code does GFP_KERNEL allocation inside
>> __link_block_group.
>> the function invokes kobject_add and internally creates sysfs files
>> with the GFP_KERNEL flag set.
>
> Yep, that's a bug.
>
>> But since do_chunk_alloc executes insides the btrfs transaction it's
>> not allowed to sleep.
>
> It's allowed to sleep but isn't allowed to do reclaim that involves file
> system writeback.  Michal Hocko's allocation context idea would fix
> this, but it's not there yet, so we'll need to defer the kobject_add
> until we can use GFP_KERNEL.

Ok, I see. Can you point out to the initial patchset?

Thanks!

>
> -Jeff
>
> --
> Jeff Mahoney
> SUSE Labs
>
>