From: Peter Xu <peterx@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
David Hildenbrand <david@redhat.com>,
Hugh Dickins <hughd@google.com>, Maya Gokhale <gokhale2@llnl.gov>,
Jerome Glisse <jglisse@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Martin Cracauer <cracauer@cons.org>,
Denis Plotnikov <dplotnikov@virtuozzo.com>,
Shaohua Li <shli@fb.com>, Andrea Arcangeli <aarcange@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Marty McFadden <mcfadden8@llnl.gov>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Mel Gorman <mgorman@suse.de>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH v5 02/25] mm: userfault: return VM_FAULT_RETRY on signals
Date: Wed, 26 Jun 2019 15:43:30 +0800 [thread overview]
Message-ID: <20190626074330.GB24379@xz-x1> (raw)
In-Reply-To: <CAHk-=wjxOz5RXpFTU=wSJg4Mjg1ugOBhBVppSTH6qjZPxpGOKg@mail.gmail.com>
On Wed, Jun 26, 2019 at 09:59:58AM +0800, Linus Torvalds wrote:
> On Tue, Jun 25, 2019 at 1:31 PM Peter Xu <peterx@redhat.com> wrote:
> >
> > Yes that sounds reasonable to me, and that matches perfectly with
> > TASK_INTERRUPTIBLE and TASK_KILLABLE. The only thing that I am a bit
> > uncertain is whether we should define FAULT_FLAG_INTERRUPTIBLE as a
> > new bit or make it simply a combination of:
> >
> > FAULT_FLAG_KILLABLE | FAULT_FLAG_USER
>
> It needs to be a new bit, I think.
>
> Some things could potentially care about the difference between "can I
> abort this thing because the task will *die* and never see the end
> result" and "can I abort this thing because it will be retried".
>
> For a regular page fault, maybe FAULT_FLAG_INTERRUPTBLE will always be
> set for the same things that set FAULT_FLAG_KILLABLE when it happens
> from user mode, but at least conceptually I think they are different,
> and it could make a difference for things like get_user_pages() or
> similar.
>
> Also, I actually don't think we should ever expose FAULT_FLAG_USER to
> any fault handlers anyway. It has a very specific meaning for memory
> cgroup handling, and no other fault handler should likely ever care
> about "was this a user fault". So I'd actually prefer for people to
> ignore and forget that hacky flag entirely, rather than give it subtle
> semantic meaning together with KILLABLE.
OK.
>
> [ Side note: this is the point where I may soon lose internet access,
> so I'll probably not be able to participate in the discussion any more
> for a while ]
Appreciate for these suggestions. I'll prepare something with that
new bit and see whether that could be accepted. I'll also try to
split those out of the bigger series.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2019-06-26 7:44 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 2:19 [PATCH v5 00/25] userfaultfd: write protection support Peter Xu
2019-06-20 2:19 ` [PATCH v5 01/25] mm: gup: rename "nonblocking" to "locked" where proper Peter Xu
2019-06-20 2:19 ` [PATCH v5 02/25] mm: userfault: return VM_FAULT_RETRY on signals Peter Xu
2019-06-22 18:02 ` Linus Torvalds
2019-06-22 18:02 ` Linus Torvalds
2019-06-24 7:42 ` Peter Xu
2019-06-24 13:31 ` Linus Torvalds
2019-06-24 13:31 ` Linus Torvalds
2019-06-25 5:30 ` Peter Xu
2019-06-26 1:59 ` Linus Torvalds
2019-06-26 1:59 ` Linus Torvalds
2019-06-26 7:43 ` Peter Xu [this message]
2019-06-20 2:19 ` [PATCH v5 03/25] userfaultfd: don't retake mmap_sem to emulate NOPAGE Peter Xu
2019-06-20 2:19 ` [PATCH v5 04/25] mm: allow VM_FAULT_RETRY for multiple times Peter Xu
2019-06-20 2:19 ` [PATCH v5 05/25] mm: gup: " Peter Xu
2019-06-20 2:19 ` [PATCH v5 06/25] userfaultfd: wp: add helper for writeprotect check Peter Xu
2019-06-20 2:19 ` [PATCH v5 07/25] userfaultfd: wp: hook userfault handler to write protection fault Peter Xu
2019-06-20 2:19 ` [PATCH v5 08/25] userfaultfd: wp: add WP pagetable tracking to x86 Peter Xu
2019-06-20 2:19 ` [PATCH v5 09/25] userfaultfd: wp: userfaultfd_pte/huge_pmd_wp() helpers Peter Xu
2019-06-20 2:19 ` [PATCH v5 10/25] userfaultfd: wp: add UFFDIO_COPY_MODE_WP Peter Xu
2019-06-20 2:19 ` [PATCH v5 11/25] mm: merge parameters for change_protection() Peter Xu
2019-06-20 2:19 ` [PATCH v5 12/25] userfaultfd: wp: apply _PAGE_UFFD_WP bit Peter Xu
2019-06-20 2:19 ` [PATCH v5 13/25] userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork Peter Xu
2019-06-20 2:19 ` [PATCH v5 14/25] userfaultfd: wp: add pmd_swp_*uffd_wp() helpers Peter Xu
2019-06-20 2:19 ` [PATCH v5 15/25] userfaultfd: wp: support swap and page migration Peter Xu
2019-06-20 2:19 ` [PATCH v5 16/25] khugepaged: skip collapse if uffd-wp detected Peter Xu
2019-06-20 2:20 ` [PATCH v5 17/25] userfaultfd: introduce helper vma_find_uffd Peter Xu
2019-06-20 2:20 ` [PATCH v5 18/25] userfaultfd: wp: support write protection for userfault vma range Peter Xu
2019-06-20 2:20 ` [PATCH v5 19/25] userfaultfd: wp: add the writeprotect API to userfaultfd ioctl Peter Xu
2019-06-20 2:20 ` [PATCH v5 20/25] userfaultfd: wp: enabled write protection in userfaultfd API Peter Xu
2019-06-20 2:20 ` [PATCH v5 21/25] userfaultfd: wp: don't wake up when doing write protect Peter Xu
2019-06-20 2:20 ` [PATCH v5 22/25] userfaultfd: wp: UFFDIO_REGISTER_MODE_WP documentation update Peter Xu
2019-06-20 2:20 ` [PATCH v5 23/25] userfaultfd: wp: declare _UFFDIO_WRITEPROTECT conditionally Peter Xu
2019-06-20 2:20 ` [PATCH v5 24/25] userfaultfd: selftests: refactor statistics Peter Xu
2019-06-20 2:20 ` [PATCH v5 25/25] userfaultfd: selftests: add write-protect test Peter Xu
2019-06-23 8:39 ` [PATCH v5 10/25] userfaultfd: wp: add UFFDIO_COPY_MODE_WP Hillf Danton
2020-02-18 3:59 ` [PATCH v5 00/25] userfaultfd: write protection support Bobby Powers
2020-02-18 3:59 ` Bobby Powers
2020-02-18 16:11 ` Peter Xu
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