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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date; bh=4hh2G7MdxNZ+MNcmp102ZgutWolekJca53oozXb1sk4=; b=VTmWXOGSMcjSN7WCjMySnx7TFqDkDjo+3TwGe7DRR8rHAAS2CqrU2opWjXE0PHDyNh zZmqWeadzdo8oLXqGqgxv49hDztQKCfO/H4wJw8zXwUSxQSsM+EwJEJz1/qaPDStT2nU f4NxcY+FhexK5kTBjkUUPLUrPK0K2AfmPjhjq/8XefvGKBocZxScB/WbwlstCpO0vKUa TTN2nvP6QBlZRNQBVLG/5XM5xljjDDtMxK5ZOviBZDfsSN/nMhrsTmex+GBKiL7eASf8 wp3jeHouEUJjaDvuV/33lefTmcNZJAxIpcLUfdDev/YQ1wwj5nXl7BaEb30wXAsMGCTu uanQ== X-Gm-Message-State: ACgBeo2eS+lCheKss97HgKNsX7UhUYc0UmeIjOGNR0Le9wI/IgPeteL/ zcd18gQkEpMzdEPgwTiH8jW3/i0sK7ls7hGdzuQrGw== X-Google-Smtp-Source: AA6agR6D9Q1KW4KNYp0SHpJ/6Fcy2IRN04G63Erd6aJSK5K6Qex+RENoU//CqGiMsVMEqkzoAOqqrGTYWrT4sPeb+8g= X-Received: by 2002:a25:cc8d:0:b0:6a8:40cb:d730 with SMTP id l135-20020a25cc8d000000b006a840cbd730mr12492178ybf.119.1662739948562; Fri, 09 Sep 2022 09:12:28 -0700 (PDT) MIME-Version: 1.0 References: <20220901173516.702122-1-surenb@google.com> <20220901173516.702122-18-surenb@google.com> <70a7d9cd-e64b-db49-e418-b4de7fcf8692@linux.ibm.com> In-Reply-To: <70a7d9cd-e64b-db49-e418-b4de7fcf8692@linux.ibm.com> From: Suren Baghdasaryan Date: Fri, 9 Sep 2022 09:12:17 -0700 Message-ID: Subject: Re: [RFC PATCH RESEND 17/28] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration To: Laurent Dufour Cc: akpm@linux-foundation.org, 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1662739949; a=rsa-sha256; cv=none; b=4vH+C41c6sGtqaqiJL5ZqS7GXy7148AAiukyG4uyY8sKxdxhufpdL+ssqwFwebLj19nHbH N9BOkqsvy5i0jjYlt9qFLbQCqXng/ZLSE3iIwkEXTHzG8cpa4RUUXM1OoXhejGOCB3EAKH EAe3elsG/21wR+I1y5X70SOUD8LmBC4= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Qz+PTfYU; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf03.hostedemail.com: domain of surenb@google.com designates 209.85.219.175 as permitted sender) smtp.mailfrom=surenb@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1662739949; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4hh2G7MdxNZ+MNcmp102ZgutWolekJca53oozXb1sk4=; b=ScS38MqEaH6VMzWCJGjMD+L9aYbhtkMZ7vziaBt1x/YaqG/yo04+1o7xpkO7/+oQU+0C8c orur28EK+zqHU5ggf7ekYSLjiTLeYuoptq9yvVCijCjpPGGwCJOeieySpVEij44kQU3gGy tbv34Yzo58R1zmLaymyn178LaacC18E= X-Stat-Signature: jx46o7ptfr7kokpkuy3k46q6k6s1wxu3 X-Rspamd-Queue-Id: 7CDA22007A X-Rspam-User: Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Qz+PTfYU; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf03.hostedemail.com: domain of surenb@google.com designates 209.85.219.175 as permitted sender) smtp.mailfrom=surenb@google.com X-Rspamd-Server: rspam12 X-HE-Tag: 1662739949-645968 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 Fri, Sep 9, 2022 at 7:20 AM Laurent Dufour wrote= : > > Le 01/09/2022 =C3=A0 19:35, Suren Baghdasaryan a =C3=A9crit : > > 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. I see. I'll double check and move the locking order. Thanks! > > > * > > * We can take all locks within these types randomly because the VM co= de > > * 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, sa= me_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 =3D mm->mmap; vma; vma =3D vma->vm_next) { > > if (vma->anon_vma) > > list_for_each_entry(avc, &vma->anon_vma_chain, sa= me_vma) >