Re: [PATCH] raid5: use memalloc_noio_save()/restore in resize_chunks()

[Guoqing Jiang <guoqing.jiang@cloud.ionos.com>]

On 15.04.20 16:23, Michal Hocko wrote:
> On Wed 15-04-20 16:10:08, Guoqing Jiang wrote:
>> On 15.04.20 13:48, Michal Hocko wrote:
>>> On Thu 09-04-20 23:38:13, Guoqing Jiang wrote:
>>> [...]
>>>> Not know memalloc_noio_{save,restore} well, but I guess it is better
>>>> to use them to mark a small scope, just my two cents.
>>> This would go against the intentio of the api. It is really meant to
>>> define reclaim recursion problematic scope.
>> Well, in current proposal, the scope is just when
>> scribble_allo/kvmalloc_array is called.
>>
>> memalloc_noio_save
>> scribble_allo/kvmalloc_array
>> memalloc_noio_restore
>>
>> With the new proposal, the marked scope would be bigger than current one
>> since there
>> are lots of places call mddev_suspend/resume.
>>
>> mddev_suspend
>> memalloc_noio_save
>> ...
>> memalloc_noio_restore
>> mddev_resume
>>
>> IMHO, if the current proposal works then what is the advantage to increase
>> the scope.
> The advantage is twofold. It serves the documentation purpose because it
> is clear _what_ and _why_ is the actual allocation restricted context.
> In this case mddev_{suspend,resume} because XYZ and you do not have to
> care about __GFP_IO for _any_ allocation inside the scope.

Personally, I'd prefer fine grained protection scope, anyway just my own
flavor. And I think Song has his opinion about the proposal, I will respect
his decision.

Thanks,
Guoqing