Re: dm ioctl: Restore __GFP_HIGH in copy_params()

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: dm ioctl: Restore __GFP_HIGH in copy_params()
Date	2017-05-23 08:10 +0200
Message-ID	<tKbb4-7G0-15@gated-at.bofh.it> (permalink)
References	(5 earlier) <tJUtA-5zo-25@gated-at.bofh.it> <tJWYp-6XB-3@gated-at.bofh.it> <tJX87-7gH-29@gated-at.bofh.it> <tJZWi-z3-11@gated-at.bofh.it> <tK2ht-1Tl-37@gated-at.bofh.it>
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On Mon 22-05-17 13:35:41, David Rientjes wrote:
> On Mon, 22 May 2017, Mike Snitzer wrote:
[...]
> > While adding the __GFP_NOFAIL flag would serve to document expectations
> > I'm left unconvinced that the memory allocator will _not fail_ for an
> > order-0 page -- as Mikulas said most ioctls don't need more than 4K.
> 
> __GFP_NOFAIL would make no sense in kvmalloc() calls, ever, it would never 
> fallback to vmalloc :)

Sorry, I could have been more specific. You would have to opencode
kvmalloc obviously. It is documented to not support this flag for the
reasons you have mentioned above.

> I'm hoping this can get merged during the 4.12 window to fix the broken 
> commit d224e9381897.

I obviously disagree. Relying on memory reserves for _correctness_ is
clearly broken by design, full stop. But it is dm code and you are going
it is responsibility of the respective maintainers to support this code.
-- 
Michal Hocko
SUSE Labs

Thread

Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Junaid Shahid <junaids@google.com> - 2017-05-19 05:00 +0200
  Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-19 09:50 +0200
    Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Mikulas Patocka <mpatocka@redhat.com> - 2017-05-20 01:50 +0200
      Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-22 11:40 +0200
        Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Mikulas Patocka <mpatocka@redhat.com> - 2017-05-22 14:10 +0200
          Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-22 14:20 +0200
            Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Mikulas Patocka <mpatocka@redhat.com> - 2017-05-22 17:00 +0200
              Re: [PATCH] dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-22 17:10 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() Mike Snitzer <snitzer@redhat.com> - 2017-05-22 20:10 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() David Rientjes <rientjes@google.com> - 2017-05-22 22:40 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() Mike Snitzer <snitzer@redhat.com> - 2017-05-23 01:40 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-23 08:10 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() Mikulas Patocka <mpatocka@redhat.com> - 2017-05-23 18:50 +0200
                Re: dm ioctl: Restore __GFP_HIGH in copy_params() Michal Hocko <mhocko@kernel.org> - 2017-05-23 09:00 +0200

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