From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C1FEFC04AB4 for ; Tue, 14 May 2019 21:19:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F06220873 for ; Tue, 14 May 2019 21:19:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="UkWlsKxO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726449AbfENVTb (ORCPT ); Tue, 14 May 2019 17:19:31 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:49306 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726134AbfENVTb (ORCPT ); Tue, 14 May 2019 17:19:31 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x4ELDlXD160157; Tue, 14 May 2019 21:19:06 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=EQWSirsGlqa3NQye335of+ycNoUAgzqdpgdwkI5ffCA=; b=UkWlsKxOm5yF3JEAAKMk7Fu3Ql4DnruLjduZWZQ8lkdO46S82VwlI9LjT6SClB+uPC4p Ug/8SzJy/TL/nViBHIATr3OZNgTB87wr3vupEMeITYrON3jcpr0jIqjvaFWnerryH+CD sru8FWnfSNp9K65VH0MPet9DFMz2XbkG4msOaLrp9GZTzEW4sc7LoMzLO4A/Adw2nfqi AOBQwOEvoqW4ROhZ/+i29aqEKuthSnYjsSsrqj4MupwzDAlPnAv1izKjghLkzQ4g58I5 nhxiL7w361QOCttpEF+1Drl1obGHyHprEzaZHPn2XSl99xRh664sZZMX9YvzGe9zoNKU VQ== Received: from userp3030.oracle.com (userp3030.oracle.com [156.151.31.80]) by aserp2130.oracle.com with ESMTP id 2sdkwds4kg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 May 2019 21:19:06 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x4ELICvE069878; Tue, 14 May 2019 21:19:05 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3030.oracle.com with ESMTP id 2sf3cnh6um-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 14 May 2019 21:19:05 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x4ELJ1tX022558; Tue, 14 May 2019 21:19:02 GMT Received: from [10.159.158.136] (/10.159.158.136) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 14 May 2019 14:19:01 -0700 Subject: Re: [PATCH v2 0/6] mm/devm_memremap_pages: Fix page release race To: Dan Williams Cc: Logan Gunthorpe , Andrew Morton , "Rafael J. Wysocki" , Greg Kroah-Hartman , linux-nvdimm , Linux Kernel Mailing List , Linux MM , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Bjorn Helgaas , Christoph Hellwig References: <155727335978.292046.12068191395005445711.stgit@dwillia2-desk3.amr.corp.intel.com> <059859ca-3cc8-e3ff-f797-1b386931c41e@deltatee.com> <17ada515-f488-d153-90ef-7a5cc5fefb0f@deltatee.com> <8a7cfa6b-6312-e8e5-9314-954496d2f6ce@oracle.com> From: Jane Chu Organization: Oracle Corporation Message-ID: <6bd8319d-3b73-bb1e-5f41-94c580ba271b@oracle.com> Date: Tue, 14 May 2019 14:18:59 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9257 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905140140 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9257 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default 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-1905140140 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/14/2019 12:04 PM, Dan Williams wrote: > On Tue, May 14, 2019 at 11:53 AM Jane Chu wrote: >> On 5/13/2019 12:22 PM, Logan Gunthorpe wrote: >> >> On 2019-05-08 11:05 a.m., Logan Gunthorpe wrote: >> >> On 2019-05-07 5:55 p.m., Dan Williams wrote: >> >> Changes since v1 [1]: >> - Fix a NULL-pointer deref crash in pci_p2pdma_release() (Logan) >> >> - Refresh the p2pdma patch headers to match the format of other p2pdma >> patches (Bjorn) >> >> - Collect Ira's reviewed-by >> >> [1]: https://lore.kernel.org/lkml/155387324370.2443841.574715745262628837.stgit@dwillia2-desk3.amr.corp.intel.com/ >> >> This series looks good to me: >> >> Reviewed-by: Logan Gunthorpe >> >> However, I haven't tested it yet but I intend to later this week. >> >> I've tested libnvdimm-pending which includes this series on my setup and >> everything works great. >> >> Just wondering in a difference scenario where pmem pages are exported to >> a KVM guest, and then by mistake the user issues "ndctl destroy-namespace -f", >> will the kernel wait indefinitely until the user figures out to kill the guest >> and release the pmem pages? > It depends on whether the pages are pinned. Typically DAX memory > mappings assigned to a guest are not pinned in the host and can be > invalidated at any time. The pinning only occurs with VFIO and > device-assignment which isn't the common case, especially since that > configuration is blocked by fsdax. However, with devdax, yes you can > arrange for the system to go into an indefinite wait. > > This somewhat ties back to the get_user_pages() vs DAX debate. The > indefinite stall issue with device-assignment could be addressed with > a requirement to hold a lease and expect that a lease revocation event > may escalate to SIGKILL in response to 'ndctl destroy-namespace'. The > expectation with device-dax is that it is already a raw interface with > pointy edges and caveats, but I would not be opposed to introducing a > lease semantic. Thanks for the quick response Dan. I am not convinced that the get_user_pages() vs FS-DAX dilemma is a perfect comparison to "ndctl destroy-namespace -f" vs namespace-is-busy dilemma. Others might disagree with me, I thought that there is no risk of panic if we fail "ndctl destroy-namespace -f" to honor a clean shutdown of the user application. Also, both actions are on the same host, so in theory the admin could shutdown the application before attempt a destructive action. By allowing 'opposite' actions in competition with each other at fine granularity, there is potential for panic in general, not necessarily with pinned page I guess. I just ran an experiment and panic'd the system. So, as Optane DCPMEM is generally for server/cloud deployment, and as RAS is a priority for server over administrative commands, to allow namespace management command to panic kernel is not an option? Here is my stress experiment - Start out with ./create_nm.sh to create as many 48G devdax namespaces as possible. Once that's completed, firing up 6 actions in quick successions in below order:  -> ndctl destroy-namespace all -f -> ./create_nm.sh -> ndctl destroy-namespace all -f -> ./create_nm.sh -> ndctl destroy-namespace all -f -> ./create_nm.sh ========== console message ======= Kernel 5.1.0-rc7-next-20190501-libnvdimm-pending on an x86_64 ban25uut130 login: [ 1620.866813] BUG: kernel NULL pointer dereference, address: 0000000000000020 [ 1620.874585] #PF: supervisor read access in kernel mode [ 1620.880319] #PF: error_code(0x0000) - not-present page [ 1620.886052] PGD 0 P4D 0 [ 1620.888879] Oops: 0000 [#1] SMP NOPTI [ 1620.892964] CPU: 19 PID: 5611 Comm: kworker/u130:3 Tainted: G W 5.1.0-rc7-next-20190501-libnvdimm-pending #5 [ 1620.905389] Hardware name: Oracle Corporation ORACLE SERVER X8-2L/ASM,MTHRBD,2U, BIOS 52020101 05/07/2019 [ 1620.916069] Workqueue: events_unbound async_run_entry_fn [ 1620.921997] RIP: 0010:klist_put+0x1b/0x6c [ 1620.926471] Code: 48 8b 43 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 55 48 89 e5 41 56 41 89 f6 41 55 41 54 53 4c 8b 27 48 89 fb 49 83 e4 fe 4c 89 e7 <4d> 8b 6c 24 20 e8 3a d4 01 00 45 84 f6 74 10 48 8b 03 a8 01 74 02 [ 1620.947427] RSP: 0018:ffffb1a5e6727da0 EFLAGS: 00010246 [ 1620.953258] RAX: ffff956796604c00 RBX: ffff956796604c28 RCX: 0000000000000000 [ 1620.961223] RDX: ffff955000c2c4d8 RSI: 0000000000000001 RDI: 0000000000000000 [ 1620.969185] RBP: ffffb1a5e6727dc0 R08: 0000000000000002 R09: ffffffffbb54b3c0 [ 1620.977150] R10: ffffb1a5e6727d40 R11: fefefefefefefeff R12: 0000000000000000 [ 1620.985116] R13: ffff94d18dcfd000 R14: 0000000000000001 R15: ffff955000caf140 [ 1620.993081] FS: 0000000000000000(0000) GS:ffff95679f4c0000(0000) knlGS:0000000000000000 [ 1621.002113] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1621.008524] CR2: 0000000000000020 CR3: 0000009fa100a005 CR4: 00000000007606e0 [ 1621.016487] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1621.024450] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1621.032413] PKRU: 55555554 [ 1621.035433] Call Trace: [ 1621.038161] klist_del+0xe/0x10 [ 1621.041667] device_del+0x8a/0x2c9 [ 1621.045463] ? __switch_to_asm+0x34/0x70 [ 1621.049840] ? __switch_to_asm+0x40/0x70 [ 1621.054220] device_unregister+0x44/0x4f [ 1621.058603] nd_async_device_unregister+0x22/0x2d [libnvdimm] [ 1621.065016] async_run_entry_fn+0x47/0x15a [ 1621.069588] process_one_work+0x1a2/0x2eb [ 1621.074064] worker_thread+0x1b8/0x26e [ 1621.078239] ? cancel_delayed_work_sync+0x15/0x15 [ 1621.083490] kthread+0xf8/0xfd [ 1621.086897] ? kthread_destroy_worker+0x45/0x45 [ 1621.091954] ret_from_fork+0x1f/0x40 [ 1621.095944] Modules linked in: xt_REDIRECT xt_nat xt_CHECKSUM iptable_mangle xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 tun bridge stp llc ebtable_filter ebtables ip6table_filter iptable_filter scsi_transport_iscsi ip6table_nat ip6_tables iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 vfat fat skx_edac intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iTCO_wdt iTCO_vendor_support aesni_intel ipmi_si crypto_simd cryptd glue_helper ipmi_devintf ipmi_msghandler sg pcspkr dax_pmem_compat device_dax dax_pmem_core i2c_i801 pcc_cpufreq lpc_ich ioatdma wmi nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c nd_pmem nd_btt sr_mod cdrom sd_mod mgag200 drm_kms_helper syscopyarea crc32c_intel sysfillrect sysimgblt fb_sys_fops ttm megaraid_sas drm igb ahci libahci ptp libata pps_core dca i2c_algo_bit nfit libnvdimm uas usb_storage dm_mirror dm_region_hash dm_log dm_mod [ 1621.189449] CR2: 0000000000000020 [ 1621.193169] ---[ end trace 7c3f7029ef24aa5a ]--- [ 1621.305383] RIP: 0010:klist_put+0x1b/0x6c [ 1621.309860] Code: 48 8b 43 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 55 48 89 e5 41 56 41 89 f6 41 55 41 54 53 4c 8b 27 48 89 fb 49 83 e4 fe 4c 89 e7 <4d> 8b 6c 24 20 e8 3a d4 01 00 45 84 f6 74 10 48 8b 03 a8 01 74 02 [ 1621.330809] RSP: 0018:ffffb1a5e6727da0 EFLAGS: 00010246 [ 1621.336642] RAX: ffff956796604c00 RBX: ffff956796604c28 RCX: 0000000000000000 [ 1621.344606] RDX: ffff955000c2c4d8 RSI: 0000000000000001 RDI: 0000000000000000 [ 1621.352570] RBP: ffffb1a5e6727dc0 R08: 0000000000000002 R09: ffffffffbb54b3c0 [ 1621.360533] R10: ffffb1a5e6727d40 R11: fefefefefefefeff R12: 0000000000000000 [ 1621.368496] R13: ffff94d18dcfd000 R14: 0000000000000001 R15: ffff955000caf140 [ 1621.376460] FS: 0000000000000000(0000) GS:ffff95679f4c0000(0000) knlGS:0000000000000000 [ 1621.385490] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1621.391902] CR2: 0000000000000020 CR3: 0000009fa100a005 CR4: 00000000007606e0 [ 1621.399867] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1621.407830] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1621.415793] PKRU: 55555554 [ 1621.418814] Kernel panic - not syncing: Fatal exception [ 1621.424740] Kernel Offset: 0x39000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 1621.550711] ---[ end Kernel panic - not syncing: Fatal exception ]--- Thanks! -jane