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Tue, 6 Sep 2022 14:34:04 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2103CA405F; Tue, 6 Sep 2022 14:37:33 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1783A4054; Tue, 6 Sep 2022 14:37:31 +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 14:37:31 +0000 (GMT) Message-ID: Date: Tue, 6 Sep 2022 16:37:31 +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 07/28] kernel/fork: mark VMAs as locked before copying pages during fork Content-Language: fr To: Suren Baghdasaryan , akpm@linux-foundation.org References: <20220901173516.702122-1-surenb@google.com> <20220901173516.702122-8-surenb@google.com> From: Laurent Dufour In-Reply-To: <20220901173516.702122-8-surenb@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: mfguNNVm0_tm7y6g6IsvzoVzzb6lC0DJ X-Proofpoint-ORIG-GUID: KUCBt6EYsH8QfRM1q5ERagYwC0h9nhBV X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.528,FMLib:17.11.122.1 definitions=2022-09-06_07,2022-09-06_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 adultscore=0 mlxscore=0 impostorscore=0 suspectscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 spamscore=0 phishscore=0 mlxlogscore=956 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2207270000 definitions=main-2209060070 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: michel@lespinasse.org, joelaf@google.com, songliubraving@fb.com, mhocko@suse.com, david@redhat.com, peterz@infradead.org, bigeasy@linutronix.de, peterx@redhat.com, dhowells@redhat.com, linux-mm@kvack.org, jglisse@google.com, dave@stgolabs.net, minchan@google.com, x86@kernel.org, hughd@google.com, willy@infradead.org, laurent.dufour@fr.ibm.com, mgorman@suse.de, rientjes@google.com, axelrasmussen@google.com, kernel-team@android.com, paulmck@kernel.org, liam.howlett@oracle.com, luto@kernel.org, vbabka@suse.cz, linux-arm-kernel@lists.infradead.org, kent.overstreet@linux.dev, linux-kernel@vger.kernel.org, hannes@cmpxchg.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit : > Protect VMAs from concurrent page fault handler while performing > copy_page_range for VMAs having VM_WIPEONFORK flag set. I'm wondering why is that necessary. The copied mm is write locked, and the destination one is not reachable. If any other readers are using the VMA, this is only for page fault handling. I should have miss something because I can't see any need to mark the lock VMA here. > Signed-off-by: Suren Baghdasaryan > --- > kernel/fork.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index bfab31ecd11e..1872ad549fed 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -709,8 +709,10 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, > rb_parent = &tmp->vm_rb; > > mm->map_count++; > - if (!(tmp->vm_flags & VM_WIPEONFORK)) > + if (!(tmp->vm_flags & VM_WIPEONFORK)) { > + vma_mark_locked(mpnt); > retval = copy_page_range(tmp, mpnt); > + } > > if (tmp->vm_ops && tmp->vm_ops->open) > tmp->vm_ops->open(tmp);