linux-kernel - Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations in blkcg

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Message-ID: <d50f16b5-296f-9c30-b61a-288aaef49e7e@suse.cz>
Date:   Tue, 29 Nov 2016 17:57:08 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marc MERLIN <marc@...lins.org>
Subject: Re: [PATCH] block,blkcg: use __GFP_NOWARN for best-effort allocations
 in blkcg

On 11/29/2016 05:38 PM, Tejun Heo wrote:
> On Tue, Nov 29, 2016 at 08:25:07AM +0100, Michal Hocko wrote:
>> --- a/include/linux/gfp.h
>> +++ b/include/linux/gfp.h
>> @@ -246,7 +246,7 @@ struct vm_area_struct;
>>  #define GFP_ATOMIC	(__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM)
>>  #define GFP_KERNEL	(__GFP_RECLAIM | __GFP_IO | __GFP_FS)
>>  #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)
>> -#define GFP_NOWAIT	(__GFP_KSWAPD_RECLAIM)
>> +#define GFP_NOWAIT	(__GFP_KSWAPD_RECLAIM|__GFP_NOWARN)
>>  #define GFP_NOIO	(__GFP_RECLAIM)
>>  #define GFP_NOFS	(__GFP_RECLAIM | __GFP_IO)
>>  #define GFP_TEMPORARY	(__GFP_RECLAIM | __GFP_IO | __GFP_FS | \
>>
>> this will not catch users who are doing gfp & ~__GFP_DIRECT_RECLAIM but
>> I would rather not make warn_alloc() even more cluttered with checks.
>
> Yeah, FWIW, looks good to me.

Me too. Just don't forget to update the comment describing GFP_NOWAIT and check 
the existing users if duplicite __GFP_NOWARN can be removed, and if they really 
want to be doing GFP_NOWAIT and not GFP_ATOMIC.

Also dunno what about Tejun's eariler patch.