From: "Ahmed S. Darwish" <a.darwish@linutronix.de> To: Jason Gunthorpe <jgg@nvidia.com> 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 18:17:16 +0100 Message-ID: <20201106171716.GA91138@lx-t490> (raw) In-Reply-To: <2-v3-7358966cab09+14e9-gup_fork_jgg@nvidia.com> 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. (I guess you just missed changing that last one... I'm in process of changing all these "*_seqcount_t_*" stuff to "do_*" as we talked on the v2 thread. Hopefully there will be no more confusion after that.) Kind regards, -- Ahmed S. Darwish Linutronix GmbH
next prev parent reply index Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <0-v3-7358966cab09+14e9-gup_fork_jgg@nvidia.com> 2020-11-06 15:55 ` [PATCH v3 1/2] mm: reorganize internal_get_user_pages_fast() Jason Gunthorpe [not found] ` <2-v3-7358966cab09+14e9-gup_fork_jgg@nvidia.com> 2020-11-06 17:17 ` Ahmed S. Darwish [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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