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Tue, 6 Sep 2022 15:44:50 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3A287A405B; Tue, 6 Sep 2022 15:44:50 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 15515A4054; Tue, 6 Sep 2022 15:44:49 +0000 (GMT) Received: from [9.101.4.33] (unknown [9.101.4.33]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 6 Sep 2022 15:44:49 +0000 (GMT) Message-ID: <70d59f18-472b-489c-ca4e-50e7d992b93e@linux.ibm.com> Date: Tue, 6 Sep 2022 17:44:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: [RFC PATCH RESEND 11/28] mm/mmap: mark VMAs as locked before merging or splitting them 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> <20220901173516.702122-12-surenb@google.com> From: Laurent Dufour In-Reply-To: <20220901173516.702122-12-surenb@google.com> Content-Type: text/plain; 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dmarc=pass (policy=none) header.from=ibm.com X-Stat-Signature: 41syqrypsfiiymsbq6nctbtffdntbops X-Rspamd-Queue-Id: 160B91C0099 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1662479107-665797 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 19:34, Suren Baghdasaryan a écrit : > Decisions about whether VMAs can be merged or split must be made while > VMAs are protected from the changes which can affect that decision. > For example, merge_vma uses vma->anon_vma in its decision whether the > VMA can be merged. Meanwhile, page fault handler changes vma->anon_vma > during COW operation. > Mark all VMAs which might be affected by a merge or split operation as > locked before making decision how such operations should be performed. > > Signed-off-by: Suren Baghdasaryan > --- > mm/mmap.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index ed58cf0689b2..ade3909c89b4 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1147,10 +1147,17 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, > if (vm_flags & VM_SPECIAL) > return NULL; > > + if (prev) > + vma_mark_locked(prev); > next = vma_next(mm, prev); > area = next; > - if (area && area->vm_end == end) /* cases 6, 7, 8 */ > + if (area) > + vma_mark_locked(area); > + if (area && area->vm_end == end) { /* cases 6, 7, 8 */ > next = next->vm_next; > + if (next) > + vma_mark_locked(next); > + } > > /* verify some invariant that must be enforced by the caller */ > VM_WARN_ON(prev && addr <= prev->vm_start); > @@ -2687,6 +2694,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, > struct vm_area_struct *new; > int err; > > + vma_mark_locked(vma); > if (vma->vm_ops && vma->vm_ops->may_split) { > err = vma->vm_ops->may_split(vma, addr); > if (err) That looks good to me, the new VMA allocated by vm_area_dup(vma) is inheriting the locked state from vma. Reviewed-by: Laurent Dufour