From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Leon Romanovsky <leonro@nvidia.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Nick Piggin <npiggin@gmail.com>, Peter Xu <peterx@redhat.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
John Hubbard <jhubbard@nvidia.com>, Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Michal Hocko <mhocko@suse.com>,
Kirill Shutemov <kirill@shutemov.name>,
Hugh Dickins <hughd@google.com>
Subject: Re: [RFC PATCH] mm: Fetch the dirty bit before we reset the pte
Date: Thu, 8 Oct 2020 10:06:34 -0700 [thread overview]
Message-ID: <CAHk-=wj0q-_n_uEwgvjHNeVsj=j4Z+wY8_dYNwDPVrpfJi6wRA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whwY0WT046fqM-zdHu9vamUjgkvmd36gCd4qSaeYy98nA@mail.gmail.com>
[ Just adding Leon to the participants ]
This patch (not attached again, Leon has seen it before) has been
tested for the last couple of weeks for the rdma case, so I have no
problems applying it now, just to keep everybody in the loop.
Linus
On Thu, Oct 8, 2020 at 10:02 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Oct 8, 2020 at 2:27 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:
> >
> > In copy_present_page, after we mark the pte non-writable, we should
> > check for previous dirty bit updates and make sure we don't lose the dirty
> > bit on reset.
>
> No, we'll just remove that entirely.
>
> Do you have a test-case that shows a problem? I have a patch that I
> was going to delay until 5.10 because I didn't think it mattered in
> practice..
>
> The second part of this patch would be to add a sequence count
> protection to fast-GUP pinning, so that GUP and fork() couldn't race,
> but I haven't written that part.
>
> Here's the first patch anyway. If you actually have a test-case where
> this matters, I guess I need to apply it now..
>
> Linus
WARNING: multiple messages have this Message-ID (diff)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Leon Romanovsky <leonro@nvidia.com>
Cc: Michal Hocko <mhocko@suse.com>, Jan Kara <jack@suse.cz>,
Linux-MM <linux-mm@kvack.org>, Hugh Dickins <hughd@google.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Xu <peterx@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
Nick Piggin <npiggin@gmail.com>,
John Hubbard <jhubbard@nvidia.com>,
Kirill Shutemov <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [RFC PATCH] mm: Fetch the dirty bit before we reset the pte
Date: Thu, 8 Oct 2020 10:06:34 -0700 [thread overview]
Message-ID: <CAHk-=wj0q-_n_uEwgvjHNeVsj=j4Z+wY8_dYNwDPVrpfJi6wRA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whwY0WT046fqM-zdHu9vamUjgkvmd36gCd4qSaeYy98nA@mail.gmail.com>
[ Just adding Leon to the participants ]
This patch (not attached again, Leon has seen it before) has been
tested for the last couple of weeks for the rdma case, so I have no
problems applying it now, just to keep everybody in the loop.
Linus
On Thu, Oct 8, 2020 at 10:02 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Thu, Oct 8, 2020 at 2:27 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:
> >
> > In copy_present_page, after we mark the pte non-writable, we should
> > check for previous dirty bit updates and make sure we don't lose the dirty
> > bit on reset.
>
> No, we'll just remove that entirely.
>
> Do you have a test-case that shows a problem? I have a patch that I
> was going to delay until 5.10 because I didn't think it mattered in
> practice..
>
> The second part of this patch would be to add a sequence count
> protection to fast-GUP pinning, so that GUP and fork() couldn't race,
> but I haven't written that part.
>
> Here's the first patch anyway. If you actually have a test-case where
> this matters, I guess I need to apply it now..
>
> Linus
next prev parent reply other threads:[~2020-10-08 17:06 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 9:26 [RFC PATCH] mm: Fetch the dirty bit before we reset the pte Aneesh Kumar K.V
2020-10-08 9:26 ` Aneesh Kumar K.V
2020-10-08 17:02 ` Linus Torvalds
2020-10-08 17:02 ` Linus Torvalds
2020-10-08 17:02 ` Linus Torvalds
2020-10-08 17:06 ` Linus Torvalds [this message]
2020-10-08 17:06 ` Linus Torvalds
2020-10-08 17:06 ` Linus Torvalds
2020-10-08 17:30 ` Linus Torvalds
2020-10-08 17:30 ` Linus Torvalds
2020-10-08 17:30 ` Linus Torvalds
2020-10-08 17:32 ` Aneesh Kumar K.V
2020-10-08 17:32 ` Aneesh Kumar K.V
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