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[148.163.156.1]) by mx.google.com with ESMTPS id 83si3416766ybp.376.2019.04.24.07.58.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 24 Apr 2019 07:58:08 -0700 (PDT) Received-SPF: pass (google.com: domain of ldufour@linux.ibm.com designates 148.163.156.1 as permitted sender) client-ip=148.163.156.1; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ldufour@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=ldufour@linux.ibm.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=ibm.com Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3OEsbdH029790 for ; Wed, 24 Apr 2019 10:58:08 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2s2rc7nxud-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 24 Apr 2019 10:58:07 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 24 Apr 2019 15:57:55 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3OEvrA663176882 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 24 Apr 2019 14:57:53 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6642AAE04D; Wed, 24 Apr 2019 14:57:53 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 93EFBAE051; Wed, 24 Apr 2019 14:57:50 +0000 (GMT) Received: from [9.145.176.48] (unknown [9.145.176.48]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 24 Apr 2019 14:57:50 +0000 (GMT) Subject: Re: [PATCH v12 23/31] mm: don't do swap readahead during speculative page fault To: Jerome Glisse Cc: akpm@linux-foundation.org, mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz, Matthew Wilcox , aneesh.kumar@linux.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org, Thomas Gleixner , Ingo Molnar , hpa@zytor.com, Will Deacon , Sergey Senozhatsky , sergey.senozhatsky.work@gmail.com, Andrea Arcangeli , Alexei Starovoitov , kemi.wang@intel.com, Daniel Jordan , David Rientjes , Ganesh Mahendran , Minchan Kim , Punit Agrawal , vinayak menon , Yang Shi , zhong jiang , Haiyan Song , Balbir Singh , sj38.park@gmail.com, Michel Lespinasse , Mike Rapoport , linux-kernel@vger.kernel.org, linux-mm@kvack.org, haren@linux.vnet.ibm.com, npiggin@gmail.com, paulmck@linux.vnet.ibm.com, Tim Chen , linuxppc-dev@lists.ozlabs.org, x86@kernel.org, Vinayak Menon References: <20190416134522.17540-1-ldufour@linux.ibm.com> <20190416134522.17540-24-ldufour@linux.ibm.com> <20190422213611.GN14666@redhat.com> From: Laurent Dufour Date: Wed, 24 Apr 2019 16:57:50 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190422213611.GN14666@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19042414-0016-0000-0000-000002732720 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19042414-0017-0000-0000-000032CF99CC Message-Id: <42ba3103-cbac-199f-e6f1-0fbc12aaccc8@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-24_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904240116 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 22/04/2019 à 23:36, Jerome Glisse a écrit : > On Tue, Apr 16, 2019 at 03:45:14PM +0200, Laurent Dufour wrote: >> Vinayak Menon faced a panic because one thread was page faulting a page in >> swap, while another one was mprotecting a part of the VMA leading to a VMA >> split. >> This raise a panic in swap_vma_readahead() because the VMA's boundaries >> were not more matching the faulting address. >> >> To avoid this, if the page is not found in the swap, the speculative page >> fault is aborted to retry a regular page fault. >> >> Reported-by: Vinayak Menon >> Signed-off-by: Laurent Dufour > > Reviewed-by: Jérôme Glisse > > Note that you should also skip non swap entry in do_swap_page() when doing > speculative page fault at very least you need to is_device_private_entry() > case. > > But this should either be part of patch 22 or another patch to fix swap > case. Thanks Jérôme, Yes I missed that, I guess the best option would be to abort on non swap entry. I'll add that in the patch 22. >> --- >> mm/memory.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index 6e6bf61c0e5c..1991da97e2db 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -2900,6 +2900,17 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) >> lru_cache_add_anon(page); >> swap_readpage(page, true); >> } >> + } else if (vmf->flags & FAULT_FLAG_SPECULATIVE) { >> + /* >> + * Don't try readahead during a speculative page fault >> + * as the VMA's boundaries may change in our back. >> + * If the page is not in the swap cache and synchronous >> + * read is disabled, fall back to the regular page >> + * fault mechanism. >> + */ >> + delayacct_clear_flag(DELAYACCT_PF_SWAPIN); >> + ret = VM_FAULT_RETRY; >> + goto out; >> } else { >> page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, >> vmf); >> -- >> 2.21.0 >> >