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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 04B74C433F5 for ; Sat, 12 Feb 2022 12:25:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234983AbiBLMZV (ORCPT ); Sat, 12 Feb 2022 07:25:21 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:43784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234999AbiBLMZU (ORCPT ); Sat, 12 Feb 2022 07:25:20 -0500 Received: from mail-m2836.qiye.163.com (mail-m2836.qiye.163.com [103.74.28.36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25C0024BE5 for ; Sat, 12 Feb 2022 04:25:15 -0800 (PST) Received: from [192.168.0.234] (unknown [218.94.118.90]) by mail-m2836.qiye.163.com (Hmail) with ESMTPA id 27DF9C020C; Sat, 12 Feb 2022 20:25:12 +0800 (CST) Message-ID: <5b4ae28e-8b0c-20b4-00eb-53e2076b47ba@easystack.cn> Date: Sat, 12 Feb 2022 20:25:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH] bcache: fixup multiple threads crash Content-Language: en-US To: Coly Li Cc: zoumingzhe@qq.com, linux-bcache@vger.kernel.org References: <20220211063915.4101-1-mingzhe.zou@easystack.cn> <8c7314c0-4df3-5bda-f17c-7ddc15de7ffc@suse.de> <214c96f8-dc8e-5511-ec85-40d945cf3a7c@easystack.cn> <551d44a7-8e87-2100-e395-04de8e1e45c3@suse.de> From: Zou Mingzhe In-Reply-To: <551d44a7-8e87-2100-e395-04de8e1e45c3@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-HM-Spam-Status: e1kfGhgUHx5ZQUtXWQgPGg8OCBgUHx5ZQUlOS1dZCBgUCR5ZQVlLVUtZV1 kWDxoPAgseWUFZKDYvK1lXWShZQUlCN1dZLVlBSVdZDwkaFQgSH1lBWUJIGE1WSUxIHkgZTE5CHx 5KVRkRExYaEhckFA4PWVdZFhoPEhUdFFlBWVVLWQY+ X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6Mxg6TTo5HTI0GQs1F1YYDD80 FTcKCVZVSlVKTU9PTU1DTEpJTktCVTMWGhIXVRYSFRwBEx5VARQOOx4aCAIIDxoYEFUYFUVZV1kS C1lBWUlKQ1VCT1VKSkNVQktZV1kIAVlBSkpMQk03Bg++ X-HM-Tid: 0a7eede4f551841ekuqw27df9c020c Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org 在 2022/2/11 19:38, Coly Li 写道: > On 2/11/22 4:57 PM, Zou Mingzhe wrote: >> >> 在 2022/2/11 16:39, Coly Li 写道: >>> On 2/11/22 2:39 PM, mingzhe.zou@easystack.cn wrote: >>>> From: Mingzhe Zou >>>> >>>> When multiple threads to check btree nodes in parallel, the main >>>> thread wait for all threads to stop or CACHE_SET_IO_DISABLE flag: >>>> >>>> wait_event_interruptible(check_state->wait, >>>> atomic_read(&check_state->started) == 0 || >>>>                           test_bit(CACHE_SET_IO_DISABLE, &c->flags)); >>>> >>>> However, the bch_btree_node_read and bch_btree_node_read_done >>>> maybe call bch_cache_set_error, then the CACHE_SET_IO_DISABLE >>>> will be set. If the flag already set, the main thread return >>>> error. At the same time, maybe some threads still running and >>>> read NULL pointer, the kernel will crash. >>> >>> Hi Mingzhe, >>> >>> Could you please explain a bit more about "read NULL pointer"? Which >>> NULL pointer might be read in the above condition? >>> >>> Thanks. >>> >>> Coly Li >> >> Hi ColyLi: >> >> >> This is dmesg output information: >> >> [956549.478889] bcache: bch_cache_set_error() bcache: error on >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8: >> [956549.492265] unsupported bset version at bucket 78226, block 0, >> 282468165 keys >> [956549.492266] bcache: bch_cache_set_error() , disabling caching > > What happens here? It seems the btree node is corrupted with > unexpected bset version. > > >> >> [956549.531298] bcache: conditional_stop_bcache_device() >> stop_when_cache_set_failed of escache2 is "auto" and cache is dirty, >> stop it to avoid potential data corruption. >> [956549.557162] bcache: cached_dev_detach_finish() Caching disabled >> for sdc1 >> [956549.570292] bcache: bcache_device_free() escache2 stopped >> [956549.603434] bcache: cache_set_free() Cache set >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8 unregistered[956583.000094] >> bcache: bch_cache_set_error() bcache: error on >> 4f45b0b1-32ea-4d83-a2b1-caa169a95b35: >> [956583.013567] unsupported bset version at bucket 25452, block 0, >> 208758840 keys >> [956583.013569] bcache: bch_cache_set_error() , disabling caching > > Similar corrupted btree node here. > > The corrupted btree node should be the first thing to look into. > > >> >> [956583.053296] bcache: conditional_stop_bcache_device() >> stop_when_cache_set_failed of escache1 is "auto" and cache is dirty, >> stop it to avoid potential data corruption. >> [956583.079968] bcache: cached_dev_detach_finish() Caching disabled >> for sdd1 >> [956583.093539] bcache: bcache_device_free() escache1 stopped >> [956583.126677] bcache: cache_set_free() Cache set >> 4f45b0b1-32ea-4d83-a2b1-caa169a95b35 unregistered >> [956589.522067]  sdc: sdc1 >> [956590.291748] bcache: register_bdev() registered backing device sdc1 >> [956590.307925] bcache: cache_alloc() set >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8 with btree_buckets: 256, free: >> 128, free_inc: 11264, heap: 22528 >> >> [956590.406700] bcache: bch_cache_set_error() bcache: error on >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8: >> [956590.411369] bcache: bch_cache_set_error() CACHE_SET_IO_DISABLE >> already set >> [956590.412453] bcache: bch_cache_set_error() CACHE_SET_IO_DISABLE >> already set >> [956590.412455] bcache: bch_cache_set_error() bcache: error on >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8: >> [956590.412456] io error reading bucket 81152 >> [956590.412456] bcache: bch_cache_set_error() , disabling caching >> >> [956590.412578] BUG: unable to handle kernel NULL pointer dereference >> at 0000000000000010 >> [956590.412594] PGD 0 P4D 0 >> [956590.412624] Oops: 0000 [#1] SMP PTI >> [956590.412645] CPU: 12 PID: 55477 Comm: bch_btrchk[9] Kdump: loaded >> Tainted: G           OE    --------- -  - >> 4.18.0-147.5.1.el8_1.5es.16.x86_64 #1 >> [956590.412646] Hardware name: Tsinghua Tongfang THTF Chaoqiang >> Server/072T6D, BIOS 2.4.3 01/17/2017 >> [956590.412859] RIP: 0010:bch_btree_node_read_done+0x1e9/0x400 [escache] >> [956590.412868] Code: 11 00 00 45 89 d3 0f b7 c0 41 c1 e3 09 49 89 c6 >> 41 0f af d3 49 d3 ee 4c 89 f1 48 63 d2 49 8d 1c 10 45 39 f1 0f 83 da >> 00 00 00 <4d> 8b 78 10 4c 39 7b 10 0f 85 d4 01 00 00 44 8b 43 18 41 >> 83 f8 01 >> [956590.412870] RSP: 0018:ffffac308ec4fd58 EFLAGS: 00010283 >> [956590.412882] RAX: 0000000000000200 RBX: 0000000000035600 RCX: >> 0000000000000200 >> [956590.412883] RDX: 0000000000035600 RSI: 00000000000001ab RDI: >> ffff911fcac20000 >> [956590.412889] RBP: ffff911f090f7000 R08: 0000000000000000 R09: >> 00000000000001ab >> [956590.412890] R10: 0000000000000001 R11: 0000000000000200 R12: >> ffff910fb3238000 >> [956590.412891] R13: 90135c78b99e07f5 R14: 0000000000000200 R15: >> ffff9119994b4620 >> [956590.412896] FS:  0000000000000000(0000) GS:ffff91107f980000(0000) >> knlGS:0000000000000000 >> [956590.412898] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [956590.412902] bcache: cache_set_free() Cache set >> c5f7cdbf-fe07-4bc3-99f5-47119a3d2af8 unregistered It seems that cache_set_free is called in run_cache_set's err. >> [956590.412911] CR2: 0000000000000010 CR3: 0000001534e0a002 CR4: >> 00000000003626e0 >> [956590.412925] DR0: 0000000000000000 DR1: 0000000000000000 DR2: >> 0000000000000000 >> [956590.412926] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: >> 0000000000000400 >> [956590.412928] Call Trace: >> [956590.412941]  bch_btree_node_read+0xe7/0x1a0 [escache] >> [956590.412953]  ? bch_keybuf_init+0x60/0x60 [escache] >> [956590.412976]  ? bch_ptr_invalid+0x10/0x10 [escache] >> [956590.413002]  btree_node_prefetch+0x6e/0x90 [escache] >> [956590.413025]  bch_btree_check_thread+0x15c/0x270 [escache] >> [956590.413089]  ? finish_task_switch+0xd7/0x2b0 >> [956590.413099]  ? bch_btree_check_recurse+0x1b0/0x1b0 [escache] >> [956590.413131]  kthread+0x112/0x130 >> [956590.413139]  ? kthread_flush_work_fn+0x10/0x10 >> [956590.413164]  ret_from_fork+0x35/0x40 >> [956590.413191] Modules linked in: iscsi_target_mod target_core_mod >> vhost_net vhost tap tun tcp_diag udp_diag inet_diag unix_diag ext4 >> mbcache jbd2 nbd sch_htb act_police cls_u32 sch_ingress xt_connmark >> xt_CHECKSUM ip_set ip_gre ip_tunnel gre ebtable_filter ebtables >> ip6table_filter nf_nat_pptp nf_nat_proto_gre nf_conntrack_pptp >> nf_conntrack_proto_gre veth nf_conntrack_netlink nfnetlink >> ip6table_nat ip6_tables overlay iscsi_tcp libiscsi_tcp libiscsi >> scsi_transport_iscsi vxlan ip6_udp_tunnel udp_tunnel openvswitch >> nf_nat_ipv6 nf_conncount ipt_REJECT nf_reject_ipv4 iptable_filter >> xt_conntrack iptable_mangle xt_statistic xt_nat ipt_MASQUERADE >> xt_comment xt_addrtype xt_recent xt_mark iptable_nat nf_nat_ipv4 >> nf_nat iptable_raw vfat fat intel_rapl sb_edac x86_pkg_temp_thermal >> mxm_wmi intel_powerclamp coretemp >> [956590.413654]  kvm_intel kvm irqbypass crct10dif_pclmul >> crc32_pclmul ghash_clmulni_intel intel_cstate intel_uncore >> intel_rapl_perf pcspkr mei_me mei joydev lpc_ich sg ipmi_si >> acpi_power_meter wmi escache nfsd nf_conntrack_ipv6 nf_defrag_ipv6 >> nf_conntrack_ipv4 nf_defrag_ipv4 auth_rpcgss br_netfilter bridge >> nfs_acl lockd grace stp llc sunrpc nf_conntrack ip_tables xfs sd_mod >> drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm >> ixgbe nvme drm ahci libahci libata nvme_core igb mdio dca >> i2c_algo_bit megaraid_sas(OE) dm_mirror dm_region_hash dm_log dm_mod >> rbd libceph dns_resolver ipmi_watchdog ipmi_devintf ipmi_msghandler >> drbd_transport_tcp(OE) drbd(OE) libcrc32c crc32c_intel >> [956590.413942] CR2: 0000000000000010 >> >> I see some print "bcache: bch_cache_set_error() bcache: error on", >> but I don't have any more information on how to go wrong. >> >> Then the 'bcache: bch_cache_set_error() CACHE_SET_IO_DISABLE already >> set' mean the CACHE_SET_IO_DISABLE flag has been set and the main >> thread will return error. >> >> At the same time, some threads is running bch_btree_check and read >> NULL pointer. >> > > As I asked before, can you tell which NULL pointer was read to trigger > the NULL pointer deference ? Then I can evaluate whether the fix is > efficient. > > [snipped] crash> bt PID: 55477  TASK: ffff9110027b5f00  CPU: 12  COMMAND: "bch_btrchk[9]"  #0 [ffffac308ec4fac0] machine_kexec at ffffffffb8c5879e  #1 [ffffac308ec4fb18] __crash_kexec at ffffffffb8d55e1d  #2 [ffffac308ec4fbe0] crash_kexec at ffffffffb8d56d1d  #3 [ffffac308ec4fbf8] oops_end at ffffffffb8c20e8d  #4 [ffffac308ec4fc18] no_context at ffffffffb8c6780e  #5 [ffffac308ec4fc70] do_page_fault at ffffffffb8c68342  #6 [ffffac308ec4fca0] page_fault at ffffffffb960114e     [exception RIP: bch_btree_node_read_done+489]     RIP: ffffffffc06c6569  RSP: ffffac308ec4fd58  RFLAGS: 00010283     RAX: 0000000000000200  RBX: 0000000000035600  RCX: 0000000000000200     RDX: 0000000000035600  RSI: 00000000000001ab  RDI: ffff911fcac20000     RBP: ffff911f090f7000   R8: 0000000000000000   R9: 00000000000001ab     R10: 0000000000000001  R11: 0000000000000200  R12: ffff910fb3238000     R13: 90135c78b99e07f5  R14: 0000000000000200  R15: ffff9119994b4620     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018  #7 [ffffac308ec4fd90] bch_btree_node_read at ffffffffc06c6867 [escache]  #8 [ffffac308ec4fe10] btree_node_prefetch at ffffffffc06c77ae [escache]  #9 [ffffac308ec4fe28] bch_btree_check_thread at ffffffffc06c881c [escache] #10 [ffffac308ec4ff10] kthread at ffffffffb8cd3542 #11 [ffffac308ec4ff50] ret_from_fork at ffffffffb9600255 crash> l *0xffffffffc06c6867 0xffffffffc06c6867 is in bch_btree_node_read (drivers/md/bcache/btree.c:271). 266 267             if (btree_node_io_error(b)) 268                     goto err; 269 270             bch_btree_node_read_done(b); 271 bch_time_stats_update(&b->c->btree_read_time, start_time); 272 273             return; 274     err: 275             bch_cache_set_error(b->c, "io error reading bucket %zu", I think the b->c maybe is the NULL pointer.