From: John Hubbard <jhubbard@nvidia.com>
To: Jann Horn <jannh@google.com>
Cc: Peter Xu <peterx@redhat.com>, Linux-MM <linux-mm@kvack.org>,
kernel list <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>,
"Kirill Shutemov" <kirill@shutemov.name>,
Oleg Nesterov <oleg@redhat.com>,
"Kirill Tkhai" <ktkhai@virtuozzo.com>,
Hugh Dickins <hughd@google.com>,
"Leon Romanovsky" <leonro@nvidia.com>, Jan Kara <jack@suse.cz>,
Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
Jason Gunthorpe <jgg@ziepe.ca>,
Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 4/5] mm: Do early cow for pinned pages during fork() for ptes
Date: Mon, 21 Sep 2020 17:08:39 -0700 [thread overview]
Message-ID: <24037577-0b96-4d8c-9487-8e788fbc29eb@nvidia.com> (raw)
In-Reply-To: <CAG48ez1Y0==PxR_h6PoRAcxTABM5o0FRR4ow+z7V3W52xNYm_w@mail.gmail.com>
On 9/21/20 3:27 PM, Jann Horn wrote:
> On Tue, Sep 22, 2020 at 12:18 AM John Hubbard <jhubbard@nvidia.com> wrote:
>> On 9/21/20 2:55 PM, Jann Horn wrote:
>>> On Mon, Sep 21, 2020 at 11:20 PM Peter Xu <peterx@redhat.com> wrote:
>> ...
> Ah... the documentation you linked implies that FOLL_WRITE should more
> or less imply FOLL_PIN? I didn't realize that.
>
hmmm, that does seem like a pretty close approximation. It's certainly
true that if we were only doing reads, and also never marking pages
dirty, that the file system writeback code would be OK.
For completeness we should add: even just reading a page is still a
problem, if one also marks the page as dirty (which is inconsistent and
wrong, but still). That's because the file system code can then break,
during writeback in particular.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2020-09-22 0:08 UTC|newest]
Thread overview: 133+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 21:17 [PATCH 0/5] mm: Break COW for pinned pages during fork() Peter Xu
2020-09-21 21:17 ` [PATCH 1/5] mm: Introduce mm_struct.has_pinned Peter Xu
2020-09-21 21:43 ` Jann Horn
2020-09-21 21:43 ` Jann Horn
2020-09-21 22:30 ` Peter Xu
2020-09-21 22:47 ` Jann Horn
2020-09-21 22:47 ` Jann Horn
2020-09-22 11:54 ` Jason Gunthorpe
2020-09-22 14:28 ` Peter Xu
2020-09-22 15:56 ` Jason Gunthorpe
2020-09-22 16:25 ` Linus Torvalds
2020-09-22 16:25 ` Linus Torvalds
2020-09-21 23:53 ` John Hubbard
2020-09-22 0:01 ` John Hubbard
2020-09-22 15:17 ` Peter Xu
2020-09-22 16:10 ` Jason Gunthorpe
2020-09-22 17:54 ` Peter Xu
2020-09-22 19:11 ` Jason Gunthorpe
2020-09-23 0:27 ` Peter Xu
2020-09-23 13:10 ` Peter Xu
2020-09-23 14:20 ` Jan Kara
2020-09-23 17:12 ` Jason Gunthorpe
2020-09-24 7:44 ` Jan Kara
2020-09-24 14:02 ` Jason Gunthorpe
2020-09-24 14:45 ` Jan Kara
2020-09-23 17:07 ` Jason Gunthorpe
2020-09-24 14:35 ` Peter Xu
2020-09-24 16:51 ` Jason Gunthorpe
2020-09-24 17:55 ` Peter Xu
2020-09-24 18:15 ` Jason Gunthorpe
2020-09-24 18:34 ` Peter Xu
2020-09-24 18:39 ` Jason Gunthorpe
2020-09-24 21:30 ` Peter Xu
2020-09-25 19:56 ` Linus Torvalds
2020-09-25 19:56 ` Linus Torvalds
2020-09-25 21:06 ` Linus Torvalds
2020-09-25 21:06 ` Linus Torvalds
2020-09-26 0:41 ` Jason Gunthorpe
2020-09-26 1:15 ` Linus Torvalds
2020-09-26 1:15 ` Linus Torvalds
2020-09-26 22:28 ` Linus Torvalds
2020-09-26 22:28 ` Linus Torvalds
2020-09-27 6:23 ` Leon Romanovsky
2020-09-27 18:16 ` Linus Torvalds
2020-09-27 18:16 ` Linus Torvalds
2020-09-27 18:45 ` Linus Torvalds
2020-09-27 18:45 ` Linus Torvalds
2020-09-28 12:49 ` Jason Gunthorpe
2020-09-28 16:17 ` Linus Torvalds
2020-09-28 16:17 ` Linus Torvalds
2020-09-28 17:22 ` Peter Xu
2020-09-28 17:54 ` Linus Torvalds
2020-09-28 17:54 ` Linus Torvalds
2020-09-28 18:39 ` Jason Gunthorpe
2020-09-28 19:29 ` Linus Torvalds
2020-09-28 19:29 ` Linus Torvalds
2020-09-28 23:57 ` Jason Gunthorpe
2020-09-29 0:18 ` John Hubbard
2020-09-28 19:36 ` Linus Torvalds
2020-09-28 19:36 ` Linus Torvalds
2020-09-28 19:50 ` Linus Torvalds
2020-09-28 19:50 ` Linus Torvalds
2020-09-28 22:51 ` Jason Gunthorpe
2020-09-29 0:30 ` Peter Xu
2020-10-08 5:49 ` Leon Romanovsky
2020-09-28 17:13 ` Peter Xu
2020-09-25 21:13 ` Peter Xu
2020-09-25 22:08 ` Linus Torvalds
2020-09-25 22:08 ` Linus Torvalds
2020-09-22 18:02 ` John Hubbard
2020-09-22 18:15 ` Peter Xu
2020-09-22 19:11 ` John Hubbard
2020-09-27 0:41 ` [mm] 698ac7610f: will-it-scale.per_thread_ops 8.2% improvement kernel test robot
2020-09-27 0:41 ` kernel test robot
2020-09-21 21:17 ` [PATCH 2/5] mm/fork: Pass new vma pointer into copy_page_range() Peter Xu
2020-09-21 21:17 ` [PATCH 3/5] mm: Rework return value for copy_one_pte() Peter Xu
2020-09-22 7:11 ` John Hubbard
2020-09-22 15:29 ` Peter Xu
2020-09-22 10:08 ` Oleg Nesterov
2020-09-22 10:18 ` Oleg Nesterov
2020-09-22 15:36 ` Peter Xu
2020-09-22 15:48 ` Oleg Nesterov
2020-09-22 16:03 ` Peter Xu
2020-09-22 16:53 ` Oleg Nesterov
2020-09-22 18:13 ` Peter Xu
2020-09-22 18:23 ` Oleg Nesterov
2020-09-22 18:49 ` Peter Xu
2020-09-23 6:52 ` Oleg Nesterov
2020-09-23 17:16 ` Linus Torvalds
2020-09-23 17:16 ` Linus Torvalds
2020-09-23 21:24 ` Linus Torvalds
2020-09-23 21:24 ` Linus Torvalds
2020-09-21 21:20 ` [PATCH 4/5] mm: Do early cow for pinned pages during fork() for ptes Peter Xu
2020-09-21 21:55 ` Jann Horn
2020-09-21 21:55 ` Jann Horn
2020-09-21 22:18 ` John Hubbard
2020-09-21 22:27 ` Jann Horn
2020-09-21 22:27 ` Jann Horn
2020-09-22 0:08 ` John Hubbard [this message]
2020-09-21 22:27 ` Peter Xu
2020-09-22 11:48 ` Oleg Nesterov
2020-09-22 12:40 ` Oleg Nesterov
2020-09-22 15:58 ` Peter Xu
2020-09-22 16:52 ` Oleg Nesterov
2020-09-22 18:34 ` Peter Xu
2020-09-22 18:44 ` Oleg Nesterov
2020-09-23 1:03 ` Peter Xu
2020-09-23 20:25 ` Linus Torvalds
2020-09-23 20:25 ` Linus Torvalds
2020-09-24 15:08 ` Peter Xu
2020-09-24 11:48 ` Kirill Tkhai
2020-09-24 15:16 ` Peter Xu
2020-09-21 21:20 ` [PATCH 5/5] mm/thp: Split huge pmds/puds if they're pinned when fork() Peter Xu
2020-09-22 6:41 ` John Hubbard
2020-09-22 10:33 ` Jan Kara
2020-09-22 20:01 ` John Hubbard
2020-09-23 9:22 ` Jan Kara
2020-09-23 13:50 ` Peter Xu
2020-09-23 14:01 ` Jan Kara
2020-09-23 15:44 ` Peter Xu
2020-09-23 20:19 ` John Hubbard
2020-09-24 18:49 ` Peter Xu
2020-09-23 16:06 ` Peter Xu
2020-09-22 12:05 ` Jason Gunthorpe
2020-09-23 15:24 ` Peter Xu
2020-09-23 16:07 ` Yang Shi
2020-09-23 16:07 ` Yang Shi
2020-09-24 15:47 ` Peter Xu
2020-09-24 17:29 ` Yang Shi
2020-09-24 17:29 ` Yang Shi
2020-09-23 17:17 ` Jason Gunthorpe
2020-09-23 10:21 ` [PATCH 0/5] mm: Break COW for pinned pages during fork() Leon Romanovsky
2020-09-23 15:37 ` Peter Xu
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