Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone

From	Andrea Arcangeli <aarcange@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone
Date	2017-08-03 23:30 +0200
Message-ID	<uavQS-5Ka-23@gated-at.bofh.it> (permalink)
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On Thu, Aug 03, 2017 at 08:24:43PM +0300, Mike Rapoport wrote:
> Now, seriously, I believe there are not many users of non-cooperative uffd
> if at all and it is very unlikely anybody has it in production.
> 
> I'll send a patch with s/ENOSPC/ESRCH in the next few days.

Ok.

Some more thought on this one, enterprise kernels have been shipped
matching the v4.11-v4.12 upstream kernel ABI and I've no time machine
to alter the kABI on those installs.

If you go ahead with the change, the safest would be that you keep
handling -ENOSPC and -ESRCH equally in CRIU code, so there will be no
risk of regression in the short term if somebody is playing with an
upstream CRIU. The alternative would be add uname -r knowledge.

Once it's upstream, I can fixup so further kernel updates will go in
sync. I obviously can't make changes that affects the kABI until it's
upstream and shipped in a official release so things will be out of
sync for a while (and the risk of somebody using ancient kernels will
persist for the mid term).

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Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Andrea Arcangeli <aarcange@redhat.com> - 2017-07-31 15:40 +0200
  Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Michal Hocko <mhocko@kernel.org> - 2017-07-31 15:50 +0200
    Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Mike Rapoport <rppt@linux.vnet.ibm.com> - 2017-08-02 14:40 +0200
      Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone "Dr. David Alan Gilbert" <dgilbert@redhat.com> - 2017-08-02 15:30 +0200
      Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Andrea Arcangeli <aarcange@redhat.com> - 2017-08-02 18:00 +0200
        Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Michal Hocko <mhocko@kernel.org> - 2017-08-02 18:30 +0200
          Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Andrea Arcangeli <aarcange@redhat.com> - 2017-08-02 18:50 +0200
            Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Mike Rapoport <rppt@linux.vnet.ibm.com> - 2017-08-03 19:30 +0200
              Re: [PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone Andrea Arcangeli <aarcange@redhat.com> - 2017-08-03 23:30 +0200

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