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Wed, 01 Mar 2023 01:54:35 -0800 (PST) Date: Wed, 1 Mar 2023 09:54:21 +0000 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@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, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, chriscli@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, leewalsh@google.com, posk@google.com, michalechner92@googlemail.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v4 24/33] mm: fall back to mmap_lock if vma->anon_vma is not yet set Message-ID: References: <20230227173632.3292573-1-surenb@google.com> <20230227173632.3292573-25-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230227173632.3292573-25-surenb@google.com> X-Rspamd-Queue-Id: F223BC000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: xjrkmc7g8cisyu9bq8e7tocnnhzec8fx X-HE-Tag: 1677664477-670678 X-HE-Meta: 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 z+ksKLYe 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 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: On Mon, Feb 27, 2023 at 09:36:23AM -0800, Suren Baghdasaryan wrote: > When vma->anon_vma is not set, page fault handler will set it by either > reusing anon_vma of an adjacent VMA if VMAs are compatible or by > allocating a new one. find_mergeable_anon_vma() walks VMA tree to find > a compatible adjacent VMA and that requires not only the faulting VMA > to be stable but also the tree structure and other VMAs inside that tree. > Therefore locking just the faulting VMA is not enough for this search. > Fall back to taking mmap_lock when vma->anon_vma is not set. This > situation happens only on the first page fault and should not affect > overall performance. > > Signed-off-by: Suren Baghdasaryan > --- > mm/memory.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index bda4c1a991f0..8855846a361b 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5243,6 +5243,10 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm, > if (!vma_is_anonymous(vma)) > goto inval; > > + /* find_mergeable_anon_vma uses adjacent vmas which are not locked */ > + if (!vma->anon_vma) > + goto inval; > + > if (!vma_start_read(vma)) > goto inval; Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > -- > 2.39.2.722.g9855ee24e9-goog > >