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>, Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Sebastian Siewior <bigeasy@linutronix.de> Subject: Re: [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Date: Tue, 3 Nov 2020 00:58:31 +0100 Message-ID: <20201102235831.GA52235@lx-t490> (raw) In-Reply-To: <2-v2-dfe9ecdb6c74+2066-gup_fork_jgg@nvidia.com> On Fri, Oct 30, 2020 at 11:46:21AM -0300, Jason Gunthorpe wrote: ... > diff --git a/mm/memory.c b/mm/memory.c > index c48f8df6e50268..294c2c3c4fe00d 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1171,6 +1171,12 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, > 0, src_vma, src_mm, addr, end); > mmu_notifier_invalidate_range_start(&range); > + /* > + * The read side doesn't spin, it goes to the mmap_lock, so the > + * raw version is used to avoid disabling preemption here > + */ > + mmap_assert_write_locked(src_mm); > + raw_write_seqcount_t_begin(&src_mm->write_protect_seq); > } > Please, s/raw_write_seqcount_t_begin()/raw_write_seqcount_begin()/g. For plain seqcount_t, it's the same, while still respecting the seqlock.h API boundaries. Let's make the comment also a bit more clear (IMHO, "lockdep" needs to be mentioned somewhere): /* * Disabling preemption is not needed for the write side, as * the read side doesn't spin, but goes to the mmap_lock. * * Use the raw variant of the seqcount_t write API to avoid * lockdep complaining about preemptibility. */ mmap_assert_write_locked(src_mm); raw_write_seqcount_t_begin(&src_mm->write_protect_seq); > ret = 0; > @@ -1187,8 +1193,10 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > } > } while (dst_pgd++, src_pgd++, addr = next, addr != end); > > - if (is_cow) > + if (is_cow) { > + raw_write_seqcount_t_end(&src_mm->write_protect_seq); ditto. s/raw_write_seqcount_t_end()/raw_write_seqcount_end()/g > mmu_notifier_invalidate_range_end(&range); > + } > return ret; > } > Thanks, -- Ahmed S. Darwish Linutronix GmbH
prev parent reply index Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <0-v2-dfe9ecdb6c74+2066-gup_fork_jgg@nvidia.com> 2020-10-30 14:46 ` [PATCH v2 1/2] mm: reorganize internal_get_user_pages_fast() Jason Gunthorpe 2020-10-30 16:29 ` Jan Kara 2020-10-30 21:31 ` John Hubbard 2020-10-30 22:36 ` Peter Xu 2020-11-02 22:19 ` [PATCH v2 0/2] Add a seqcount between gup_fast and copy_page_range() Ahmed S. Darwish 2020-11-02 22:39 ` Linus Torvalds 2020-11-02 23:18 ` Ahmed S. Darwish [not found] ` <2-v2-dfe9ecdb6c74+2066-gup_fork_jgg@nvidia.com> 2020-10-30 16:51 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Jan Kara [not found] ` <20201030170226.GF2620339@nvidia.com> 2020-11-02 8:31 ` Jan Kara 2020-10-30 22:52 ` Peter Xu [not found] ` <20201030235121.GQ2620339@nvidia.com> 2020-10-31 15:26 ` Peter Xu 2020-11-03 0:33 ` Ahmed S. Darwish 2020-11-03 0:17 ` Ahmed S. Darwish [not found] ` <20201103002532.GL2620339@nvidia.com> 2020-11-03 0:41 ` Ahmed S. Darwish 2020-11-03 2:20 ` John Hubbard 2020-11-03 6:52 ` Ahmed S. Darwish 2020-11-03 17:40 ` Linus Torvalds 2020-11-04 1:32 ` Ahmed S. Darwish 2020-11-04 2:01 ` John Hubbard 2020-11-04 3:17 ` Ahmed S. Darwish 2020-11-04 18:38 ` Linus Torvalds 2020-11-04 19:54 ` Ahmed S. Darwish 2020-12-09 18:38 ` [tip: locking/core] seqlock: Prefix internal seqcount_t-only macros with a "do_" tip-bot2 for Ahmed S. Darwish 2020-12-09 18:38 ` [tip: locking/core] seqlock: kernel-doc: Specify when preemption is automatically altered tip-bot2 for Ahmed S. Darwish 2020-11-10 11:53 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Peter Zijlstra 2020-12-03 10:35 ` [tip: locking/core] seqlock: Rename __seqprop() users tip-bot2 for Peter Zijlstra 2020-11-03 17:03 ` [PATCH v2 2/2] mm: prevent gup_fast from racing with COW during fork Peter Xu 2020-11-02 23:58 ` Ahmed S. Darwish [this message]
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