From: Jason Gunthorpe <jgg@nvidia.com>
To: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Cc: <linux-kernel@vger.kernel.org>, Peter Xu <peterx@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.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>,
John Hubbard <jhubbard@nvidia.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 Zijlstra <peterz@infradead.org>,
"Sebastian A. Siewior" <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 2/2] mm: prevent gup_fast from racing with COW during fork
Date: Fri, 6 Nov 2020 13:57:46 -0400 [thread overview]
Message-ID: <20201106175746.GX2620339@nvidia.com> (raw)
In-Reply-To: <20201106171716.GA91138@lx-t490>
On Fri, Nov 06, 2020 at 06:17:16PM +0100, Ahmed S. Darwish wrote:
> Hi Jason,
>
> On Fri, Nov 06, 2020 at 11:55:14AM -0400, Jason Gunthorpe wrote:
> ...
> > + if (gup_flags & FOLL_PIN) {
> > + seq = raw_read_seqcount(¤t->mm->write_protect_seq);
> > + if (seq & 1)
> > + return 0;
> > + }
> > +
> ...
> > + if (gup_flags & FOLL_PIN) {
> > + if (read_seqcount_t_retry(¤t->mm->write_protect_seq,
> > + seq)) {
> > + unpin_user_pages(pages, nr_pinned);
> > + return 0;
> > + }
> > + }
>
> From seqlock.h:
>
> /**
> * raw_read_seqcount() - read the raw seqcount_t counter value
> * ...
> * Return: count to be passed to read_seqcount_retry()
> */
> #define raw_read_seqcount(s)
>
> Please avoid using the internal API (read_seqcount_*t*_retry) and just
> use read_seqcount_retry() as the documentation suggests.
Oh, yes I didn't notice this one in all the discussion that spawned
from the first thread. Thanks
Jason
next prev parent reply other threads:[~2020-11-06 17:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-06 15:55 [PATCH v3 0/2] Add a seqcount between gup_fast and copy_page_range() Jason Gunthorpe
2020-11-06 15:55 ` [PATCH v3 1/2] mm: reorganize internal_get_user_pages_fast() Jason Gunthorpe
2020-11-06 15:55 ` [PATCH v3 2/2] mm: prevent gup_fast from racing with COW during fork Jason Gunthorpe
2020-11-06 17:17 ` Ahmed S. Darwish
2020-11-06 17:57 ` Jason Gunthorpe [this message]
2020-11-06 18:52 ` [PATCH v3 0/2] Add a seqcount between gup_fast and copy_page_range() Ahmed S. Darwish
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