Re: [PATCH 17/19] dm: get rid of superfluous gfp flags

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 17/19] dm: get rid of superfluous gfp flags
Date	2016-04-16 22:40 +0200
Message-ID	<roFay-WA-15@gated-at.bofh.it> (permalink)
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On Fri 15-04-16 14:41:29, Mikulas Patocka wrote:
> 
> 
> On Fri, 15 Apr 2016, Michal Hocko wrote:
> 
> > On Fri 15-04-16 08:29:28, Mikulas Patocka wrote:
> > > 
> > > 
> > > On Mon, 11 Apr 2016, Michal Hocko wrote:
> > > 
> > > > From: Michal Hocko <mhocko@suse.com>
> > > > 
> > > > copy_params seems to be little bit confused about which allocation flags
> > > > to use. It enforces GFP_NOIO even though it uses
> > > > memalloc_noio_{save,restore} which enforces GFP_NOIO at the page
> > > 
> > > memalloc_noio_{save,restore} is used because __vmalloc is flawed and 
> > > doesn't respect GFP_NOIO properly (it doesn't use gfp flags when 
> > > allocating pagetables).
> > 
> > Yes and there are no plans to change __vmalloc to properly propagate gfp
> > flags through the whole call chain and that is why we have
> > memalloc_noio thingy. If that ever changes later the GFP_NOIO can be
> > added in favor of memalloc_noio API. Both are clearly redundant.
> > -- 
> > Michal Hocko
> > SUSE Labs
> 
> You could move memalloc_noio_{save,restore} to __vmalloc. Something like
> 
> if (!(gfp_mask & __GFP_IO))
> 	noio_flag = memalloc_noio_save();
> ...
> if (!(gfp_mask & __GFP_IO))
> 	memalloc_noio_restore(noio_flag);
> 
> That would be better than repeating this hack in every __vmalloc caller 
> that need GFP_NOIO.

It is not my intention to change __vmalloc behavior. If you strongly
oppose the GFP_NOIO change I can drop it from the patch. It is
__GFP_REPEAT which I am after.

-- 
Michal Hocko
SUSE Labs

Thread

Re: [PATCH 17/19] dm: get rid of superfluous gfp flags Mikulas Patocka <mpatocka@redhat.com> - 2016-04-15 20:50 +0200
  Re: [PATCH 17/19] dm: get rid of superfluous gfp flags Michal Hocko <mhocko@kernel.org> - 2016-04-16 22:40 +0200
    Re: [PATCH 17/19] dm: get rid of superfluous gfp flags Michal Hocko <mhocko@kernel.org> - 2016-04-22 14:50 +0200
      Re: [PATCH 17/19] dm: get rid of superfluous gfp flags Mikulas Patocka <mpatocka@redhat.com> - 2016-04-26 19:30 +0200
        Re: [PATCH 17/19] dm: get rid of superfluous gfp flags Michal Hocko <mhocko@kernel.org> - 2016-04-27 10:40 +0200

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