From: John Hubbard <jhubbard@nvidia.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>,
Christoph Hellwig <hch@lst.de>, Hugh Dickins <hughd@google.com>,
Jan Kara <jack@suse.cz>, Jann Horn <jannh@google.com>,
Kirill Shutemov <kirill@shutemov.name>,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Leon Romanovsky <leonro@nvidia.com>,
Linux-MM <linux-mm@kvack.org>, "Michal Hocko" <mhocko@suse.com>,
Oleg Nesterov <oleg@redhat.com>, Peter Xu <peterx@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 2/2] mm: prevent gup_fast from racing with COW during fork
Date: Mon, 26 Oct 2020 17:35:06 -0700 [thread overview]
Message-ID: <729699ba-a6a2-4081-092f-cae6f2c5657b@nvidia.com> (raw)
In-Reply-To: <20201026234952.GD1523783@nvidia.com>
On 10/26/20 4:49 PM, Jason Gunthorpe wrote:
> On Fri, Oct 23, 2020 at 10:31:51PM -0700, John Hubbard wrote:
>> On 10/23/20 10:19 PM, John Hubbard wrote:
>>> On 10/23/20 5:19 PM, Jason Gunthorpe wrote:
>> ...
>> If so, it would still be good to wrap the "acquire" and "release"
>> parts of this into functions, IMHO. So we'd end up with,
>> effectively, a lock API anyway.
>
> What it really needs is a smp_load_mb() to match the existing smp_store_mb(),
> then this implementation wouldn't look so odd.
>
No argument there!
> It is actually really straightforwad since the write side is under the
> exclusive mmap_lock.
>
Yes, conceptually it is pretty clean. I'm still wishing there were a small API to
encapsulate such things, but given that there isn't one, I'll take another look
later tonight and attempt to spot any problems with the current patch, as-is.
"Unfortunately", I don't yet see any problems... :)
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2020-10-27 0:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-24 0:19 [PATCH 0/2] Add a 'seqcount' between gup_fast and copy_page_range Jason Gunthorpe
2020-10-24 0:19 ` [PATCH 1/2] mm: reorganize internal_get_user_pages_fast() Jason Gunthorpe
2020-10-24 4:44 ` John Hubbard
2020-10-26 23:59 ` Jason Gunthorpe
2020-10-27 9:33 ` Jan Kara
2020-10-27 9:55 ` Christoph Hellwig
2020-10-28 6:00 ` John Hubbard
2020-10-27 13:15 ` Jason Gunthorpe
2020-10-28 6:00 ` John Hubbard
2020-10-28 6:05 ` John Hubbard
2020-10-24 0:19 ` [PATCH 2/2] mm: prevent gup_fast from racing with COW during fork Jason Gunthorpe
2020-10-24 5:19 ` John Hubbard
2020-10-24 5:31 ` John Hubbard
2020-10-26 23:49 ` Jason Gunthorpe
2020-10-27 0:14 ` Linus Torvalds
2020-10-27 11:32 ` Jason Gunthorpe
2020-10-27 0:35 ` John Hubbard [this message]
2020-10-27 7:32 ` John Hubbard
2020-11-02 3:25 ` [mm] e498078ae9: will-it-scale.per_thread_ops -1.4% regression kernel test robot
2020-10-24 5:14 ` [PATCH 0/2] Add a 'seqcount' between gup_fast and copy_page_range John Hubbard
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