linux-kernel - Re: [PATCH 6/6] mm: Add memalloc

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Message-ID: <6421BC93-CF2F-4697-B5CB-5ECDAA9FCB37@kernel.org>
Date:   Mon, 29 Jun 2020 16:45:14 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
CC:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-xfs@...r.kernel.org, dm-devel@...hat.com,
        Mikulas Patocka <mpatocka@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, NeilBrown <neilb@...e.de>
Subject: Re: [PATCH 6/6] mm: Add memalloc_nowait



On June 29, 2020 3:52:31 PM GMT+03:00, Michal Hocko <mhocko@...nel.org> wrote:
>On Mon 29-06-20 13:18:16, Matthew Wilcox wrote:
>> On Mon, Jun 29, 2020 at 08:08:51AM +0300, Mike Rapoport wrote:
>> > > @@ -886,8 +868,12 @@ static struct dm_buffer
>*__alloc_buffer_wait_no_callback(struct dm_bufio_client
>> > >  			return NULL;
>> > >  
>> > >  		if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
>> > > +			unsigned noio_flag;
>> > > +
>> > >  			dm_bufio_unlock(c);
>> > > -			b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY |
>__GFP_NOMEMALLOC | __GFP_NOWARN);
>> > > +			noio_flag = memalloc_noio_save();
>> > 
>> > I've read the series twice and I'm still missing the definition of
>> > memalloc_noio_save().
>> > 
>> > And also it would be nice to have a paragraph about it in
>> > Documentation/core-api/memory-allocation.rst
>> 
>>
>Documentation/core-api/gfp_mask-from-fs-io.rst:``memalloc_nofs_save``,
>``memalloc_nofs_restore`` respectively ``memalloc_noio_save``,
>> Documentation/core-api/gfp_mask-from-fs-io.rst:   :functions:
>memalloc_noio_save memalloc_noio_restore
>> Documentation/core-api/gfp_mask-from-fs-io.rst:allows nesting so it
>is safe to call ``memalloc_noio_save`` or
> 
>The patch is adding memalloc_nowait* and I suspect Mike had that in
>mind, which would be a fair request. 

Right, sorry misprinted that.

> Btw. we are missing
>memalloc_nocma*
>documentation either - I was just reminded of its existence today..
-- 
Sincerely yours,
Mike