On Wed, 2017-02-01 at 09:13 -0800, Jens Axboe wrote:
> So that's changing the elevator - did this happen while heavy IO was
> going to the drive, or was it idle?
Hello Jens,
I think I figured out what was going on:
* Test 02-mq created scsi-mq SRP paths and multipathd created dm-mq device
nodes on top of these SRP paths.
* Test 02-sq started with removing the SRP paths and with switching the
SCSI and DM cores from mq to sq but did not remove the dm-mq device
nodes. When that test script next performed an SRP log in multipathd
failed to add the single queue SCSI devices to an existing dm-mq
device node. In other words, the dm-mq devices had queue_if_no_path
set but did not have any paths. Hence the lockup for requests sent
to these dm devices.
I have modified my tests scripts such that the dm device nodes from a
previous test are removed before a new test starts. Since I made that
change I haven't seen any I/O lockup. However, a new issue shows up
sporadically, an issue that I had not yet seen during any test with
a kernel tree from Linus:
[ 227.613440] general protection fault: 0000 [#1] SMP
[ 227.613495] Modules linked in: dm_service_time ib_srp scsi_transport_srp target_core_user uio target_core_pscsi target_core_file ib_srpt target_core_iblock target_core_mod brd netconsole xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat libcrc32c nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables af_packet ib_ipoib msr rdma_ucm ib_ucm ib_uverbs ib_umad rdma_cm configfs ib_cm iw_cm mlx4_ib ib_core sb_edac edac_core x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel ipmi_ssif kvm irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel pcbc tg3 aesni_intel iTCO_wdt mlx4_core ptp iTCO_vendor_support dcdbas aes_x86_64 crypto_simd glue_helper pps_core cryptd pcspkr devlink ipmi_si libphy ipmi_devintf fjes ipmi_msghandler tpm_tis tpm_tis_core lpc_ich mei_me mfd_core mei shpchp wmi tpm button hid_generic usbhid mgag200 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sr_mod sysimgblt fb_sys_fops cdrom ttm drm ehci_pci ehci_hcd usbcore usb_common sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua autofs4
[ 227.613774] CPU: 3 PID: 28 Comm: ksoftirqd/3 Not tainted 4.10.0-rc5-dbg+ #1
[ 227.613840] Hardware name: Dell Inc. PowerEdge R430/03XKDV, BIOS 1.0.2 11/17/2014
[ 227.613893] task: ffff880172a249c0 task.stack: ffffc90001aa8000
[ 227.613932] RIP: 0010:rq_completed+0x12/0x90 [dm_mod]
[ 227.613965] RSP: 0018:ffffc90001aabda8 EFLAGS: 00010246
[ 227.614006] RAX: 0000000000000000 RBX: 6b6b6b6b6b6b6b6b RCX: 0000000000000000
[ 227.614043] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 6b6b6b6b6b6b6b6b
[ 227.614074] RBP: ffffc90001aabdc0 R08: ffff8803825f4c38 R09: 0000000000000000
[ 227.614105] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[ 227.614137] R13: 0000000000000000 R14: ffffffff81c05120 R15: 0000000000000004
[ 227.614170] FS: 0000000000000000(0000) GS:ffff88046f2c0000(0000) knlGS:0000000000000000
[ 227.614209] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 227.614239] CR2: 0000557e28bc20d0 CR3: 000000038594e000 CR4: 00000000001406e0
[ 227.614268] Call Trace:
[ 227.614301] dm_softirq_done+0xe6/0x1e0 [dm_mod]
[ 227.614337] blk_done_softirq+0x88/0xa0
[ 227.614369] __do_softirq+0xba/0x4c0
[ 227.614470] run_ksoftirqd+0x1a/0x50
[ 227.614499] smpboot_thread_fn+0x123/0x1e0
[ 227.614529] kthread+0x107/0x140
[ 227.614624] ret_from_fork+0x2e/0x40
[ 227.614648] Code: ff ff 31 f6 48 89 c7 e8 cd 0e 2f e1 5d c3 90 66 2e 0f 1f 84 00 00 00 00 00 55 48 63 f6 48 89 e5 41 55 41 89 d5 41 54 53 48 89 fb <4c> 8b a7 88 02 00 00 f0 ff 8c b7 50 03 00 00 e8 ba 43 ff ff 85
[ 227.614738] RIP: rq_completed+0x12/0x90 [dm_mod] RSP: ffffc90001aabda8
(gdb) list *(rq_completed+0x12)
0xdd12 is in rq_completed (drivers/md/dm-rq.c:187).
182 * the md may be freed in dm_put() at the end of this function.
183 * Or do dm_get() before calling this function and dm_put() later.
184 */
185 static void rq_completed(struct mapped_device *md, int rw, bool run_queue)
186 {
187 struct request_queue *q = md->queue;
188 unsigned long flags;
189
190 atomic_dec(&md->pending[rw]);
191
(gdb) disas rq_completed
Dump of assembler code for function rq_completed:
0x000000000000dd00 <+0>: push %rbp
0x000000000000dd01 <+1>: movslq %esi,%rsi
0x000000000000dd04 <+4>: mov %rsp,%rbp
0x000000000000dd07 <+7>: push %r13
0x000000000000dd09 <+9>: mov %edx,%r13d
0x000000000000dd0c <+12>: push %r12
0x000000000000dd0e <+14>: push %rbx
0x000000000000dd0f <+15>: mov %rdi,%rbx
0x000000000000dd12 <+18>: mov 0x288(%rdi),%r12
0x000000000000dd19 <+25>: lock decl 0x350(%rdi,%rsi,4)
So this was caused by an attempt to dereference %rdi = 0x6b6b6b6b6b6b6b6b.
Hence this is probably a use-after-free of struct mapped_device.
Bart.--
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