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

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Date:   Mon, 29 Jun 2020 13:18:16 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Rapoport <rppt@...nel.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 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