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Fri, 9 Sep 2022 14:20:37 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7B70542042; Fri, 9 Sep 2022 14:20:37 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6167E4203F; Fri, 9 Sep 2022 14:20:36 +0000 (GMT) Received: from [9.145.83.17] (unknown [9.145.83.17]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 9 Sep 2022 14:20:36 +0000 (GMT) Message-ID: <70a7d9cd-e64b-db49-e418-b4de7fcf8692@linux.ibm.com> Date: Fri, 9 Sep 2022 16:20:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: [RFC PATCH RESEND 17/28] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration Content-Language: fr To: Suren Baghdasaryan , akpm@linux-foundation.org Cc: michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, laurent.dufour@fr.ibm.com, paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, kernel-team@android.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org References: <20220901173516.702122-1-surenb@google.com> <20220901173516.702122-18-surenb@google.com> From: Laurent Dufour In-Reply-To: <20220901173516.702122-18-surenb@google.com> Content-Type: text/plain; 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spf=pass (imf21.hostedemail.com: domain of ldufour@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=ldufour@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Stat-Signature: nojjtmodbqqrb3pbzmufd8d4win761qb X-Rspam-User: X-HE-Tag: 1662733250-298155 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Le 01/09/2022 à 19:35, Suren Baghdasaryan a écrit : > Pagefault handlers might need to fire MMU notifications while a new > notifier is being registered. Modify mm_take_all_locks to mark all VMAs > as locked and prevent this race with fault handlers that would hold VMA > locks. > > Signed-off-by: Suren Baghdasaryan > --- > mm/mmap.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/mmap.c b/mm/mmap.c > index b31cc97c2803..1edfcd384f5e 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -3538,6 +3538,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) > * hugetlb mapping); > * - all i_mmap_rwsem locks; > * - all anon_vma->rwseml > + * - all vmas marked locked IIRC, the anon_vma may be locked during the page fault handling, and this happens after the VMA is read lock. I think the same applies to i_mmap_rwsem lock. Thus, the VMA should be marked locked first. > * > * We can take all locks within these types randomly because the VM code > * doesn't nest them and we protected from parallel mm_take_all_locks() by > @@ -3579,6 +3580,7 @@ int mm_take_all_locks(struct mm_struct *mm) > if (vma->anon_vma) > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) > vm_lock_anon_vma(mm, avc->anon_vma); > + vma_mark_locked(vma); > } > > return 0; > @@ -3636,6 +3638,7 @@ void mm_drop_all_locks(struct mm_struct *mm) > mmap_assert_write_locked(mm); > BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); > > + vma_mark_unlocked_all(mm); > for (vma = mm->mmap; vma; vma = vma->vm_next) { > if (vma->anon_vma) > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)