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SubjectRe: [PATCH BUGFIX 1/1] block, bfq: add requeue-request hook
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> Il giorno 06 feb 2018, alle ore 19:35, Oleksandr Natalenko <oleksandr@natalenko.name> ha scritto:
>
> Hi.
>
> 06.02.2018 15:50, Paolo Valente wrote:
>> Could you please do a
>> gdb <buildir>/block/bfq-iosched.o # or vmlinux.o if bfq is builtin
>> list *(bfq_finish_requeue_request+0x54)
>> list *(bfq_put_queue+0x10b)
>> for me?
>
> Fresh crashes and gdb output are given below. A side note: it is harder to trigger things on a slower machine, so clearly some timing-bounded race condition there.
>
> [ 134.276548] BUG: unable to handle kernel NULL pointer dereference at (null)
> [ 134.283699] IP: blk_flush_complete_seq+0x20a/0x300
> [ 134.288163] PGD 0 P4D 0
> [ 134.291284] Oops: 0002 [#1] PREEMPT SMP PTI
> [ 134.293842] Modules linked in: bochs_drm ttm nls_iso8859_1 kvm_intel nls_cp437 vfat fat drm_kms_helper kvm drm irqbypass psmouse iTCO_wdt ppdev iTCO_vendor_support input_leds led_class i2c_i801 parport_pc joydev intel_agp parport intel_gtt mousedev lpc_ich rtc_cmos syscopyarea evdev sysfillrect agpgart qemu_fw_cfg mac_hid sysimgblt fb_sys_fops sch_fq_codel ip_tables x_tables xfs dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio libcrc32c crc32c_generic dm_crypt algif_skcipher af_alg dm_mod hid_generic usbhid raid10 hid md_mod sr_mod sd_mod cdrom uhci_hcd ehci_pci serio_raw crct10dif_pclmul crc32_pclmul atkbd crc32c_intel libps2 ghash_clmulni_intel pcbc xhci_pci xhci_hcd ehci_hcd aesni_intel aes_x86_64 crypto_simd glue_helper cryptd ahci libahci libata usbcore usb_common i8042 serio virtio_scsi
> [ 134.340606] scsi_mod virtio_blk virtio_net virtio_pci virtio_ring virtio
> [ 134.345803] CPU: 0 PID: 178 Comm: kworker/0:1H Not tainted 4.15.0-pf2 #1
> [ 134.350309] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> [ 134.355106] Workqueue: kblockd blk_mq_run_work_fn
> [ 134.359034] RIP: 0010:blk_flush_complete_seq+0x20a/0x300
> [ 134.367647] RSP: 0000:ffff88000f803ce8 EFLAGS: 00010082
> [ 134.371632] RAX: ffff88000d9755c0 RBX: ffff88000d9755a0 RCX: ffff88000c9b39a8
> [ 134.375675] RDX: 0000000000000000 RSI: ffff88000d9755d0 RDI: ffff88000c9b3900
> [ 134.381068] RBP: ffff88000d21a990 R08: ffff88000d9755b0 R09: 0000000000000000
> [ 134.386302] R10: ffff8800058ff100 R11: 000000000002000b R12: 0000000000000000
> [ 134.396915] R13: ffff88000d9755f0 R14: 0000000000000046 R15: ffff88000d9755a0
> [ 134.401140] FS: 0000000000000000(0000) GS:ffff88000f800000(0000) knlGS:0000000000000000
> [ 134.407361] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 134.412384] CR2: 0000000000000000 CR3: 0000000004008006 CR4: 00000000001606f0
> [ 134.416913] Call Trace:
> [ 134.420251] <IRQ>
> [ 134.427731] mq_flush_data_end_io+0xb3/0xf0
> [ 134.431848] scsi_end_request+0x90/0x1e0 [scsi_mod]
> [ 134.436424] scsi_io_completion+0x237/0x650 [scsi_mod]
> [ 134.440109] __blk_mq_complete_request+0xc4/0x150
> [ 134.444517] ? scsi_mq_get_budget+0x110/0x110 [scsi_mod]
> [ 134.449603] ata_scsi_qc_complete+0x8d/0x430 [libata]
> [ 134.458487] ata_qc_complete_multiple+0x8d/0xe0 [libata]
> [ 134.461726] ahci_handle_port_interrupt+0xc9/0x5b0 [libahci]
> [ 134.466420] ahci_handle_port_intr+0x54/0xb0 [libahci]
> [ 134.470128] ahci_single_level_irq_intr+0x3b/0x60 [libahci]
> [ 134.473327] __handle_irq_event_percpu+0x44/0x1e0
> [ 134.476700] handle_irq_event_percpu+0x30/0x70
> [ 134.480227] handle_irq_event+0x37/0x60
> [ 134.490341] handle_edge_irq+0x107/0x1c0
> [ 134.492876] handle_irq+0x1f/0x30
> [ 134.495497] do_IRQ+0x4d/0xe0
> [ 134.497963] common_interrupt+0xa2/0xa2
> [ 134.500877] </IRQ>
> [ 134.503129] RIP: 0010:_raw_spin_unlock_irqrestore+0x11/0x40
> [ 134.506782] RSP: 0000:ffffc90000307d30 EFLAGS: 00000293 ORIG_RAX: ffffffffffffffdb
> [ 134.511845] RAX: 0000000000000001 RBX: ffff88000db04000 RCX: 0000000000000008
> [ 134.523019] RDX: 0000000000000100 RSI: 0000000000000293 RDI: 0000000000000293
> [ 134.527968] RBP: 0000000000000293 R08: ffffffffffffffff R09: 0000000000000040
> [ 134.532289] R10: 00000000008e66bf R11: 000000000002000b R12: 0000000000000000
> [ 134.536376] R13: ffff88000d26a000 R14: ffff88000b99ac48 R15: ffff88000d26a000
> [ 134.541046] ata_scsi_queuecmd+0xa0/0x210 [libata]
> [ 134.544363] scsi_dispatch_cmd+0xe8/0x260 [scsi_mod]
> [ 134.552883] scsi_queue_rq+0x4cf/0x560 [scsi_mod]
> [ 134.556811] blk_mq_dispatch_rq_list+0x8f/0x4c0
> [ 134.559741] blk_mq_sched_dispatch_requests+0x105/0x190
> [ 134.563253] __blk_mq_run_hw_queue+0x80/0x90
> [ 134.565540] process_one_work+0x1df/0x420
> [ 134.568041] worker_thread+0x2b/0x3d0
> [ 134.571032] ? process_one_work+0x420/0x420
> [ 134.573964] kthread+0x113/0x130
> [ 134.584370] ? kthread_create_on_node+0x70/0x70
> [ 134.587355] ret_from_fork+0x35/0x40
> [ 134.589796] Code: 39 d0 0f 84 8f 00 00 00 48 8b 97 b0 00 00 00 49 c1 e0 04 45 31 e4 48 8b b7 a8 00 00 00 49 01 d8 48 8d 8f a8 00 00 00 48 89 56 08 <48> 89 32 49 8b 50 18 49 89 48 18 48 89 87 a8 00 00 00 48 89 97
> [ 134.598881] RIP: blk_flush_complete_seq+0x20a/0x300 RSP: ffff88000f803ce8
> [ 134.601812] CR2: 0000000000000000
> [ 134.603728] ---[ end trace fc6d0cdf33d29717 ]---
> [ 134.612349] Kernel panic - not syncing: Fatal exception in interrupt
> [ 134.615630] Kernel Offset: disabled
> [ 134.617712] ---[ end Kernel panic - not syncing: Fatal exception in interrupt
>
> (gdb) list *(blk_flush_complete_seq+0x20a)
> 0xffffffff813056ca is in blk_flush_complete_seq (./include/linux/compiler.h:212).
> 207 {
> 208 switch (size) {
> 209 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
> 210 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
> 211 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
> 212 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
> 213 default:
> 214 barrier();
> 215 __builtin_memcpy((void *)p, (const void *)res, size);
> 216 barrier();
>
> [ 231.545605] BUG: unable to handle kernel paging request at 0000001000000028
> [ 231.551962] IP: bfq_put_queue+0x10b/0x130
> [ 231.556307] PGD 0 P4D 0
> [ 231.558939] Oops: 0000 [#1] PREEMPT SMP PTI
> [ 231.562149] Modules linked in: nls_iso8859_1 nls_cp437 vfat fat kvm_intel kvm bochs_drm irqbypass ttm iTCO_wdt ppdev drm_kms_helper iTCO_vendor_support psmouse input_leds drm led_class joydev parport_pc mousedev intel_agp syscopyarea parport intel_gtt sysfillrect i2c_i801 evdev sysimgblt agpgart rtc_cmos qemu_fw_cfg mac_hid fb_sys_fops lpc_ich sch_fq_codel ip_tables x_tables xfs dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio libcrc32c crc32c_generic dm_crypt algif_skcipher af_alg dm_mod hid_generic usbhid hid raid10 md_mod sr_mod cdrom sd_mod serio_raw atkbd libps2 uhci_hcd crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel pcbc xhci_pci aesni_intel aes_x86_64 ehci_pci xhci_hcd ehci_hcd ahci crypto_simd glue_helper libahci cryptd usbcore libata usb_common i8042 serio virtio_scsi
> [ 231.608289] scsi_mod virtio_blk virtio_net virtio_pci virtio_ring virtio
> [ 231.613610] CPU: 0 PID: 187 Comm: kworker/0:1H Not tainted 4.15.0-pf2 #1
> [ 231.619675] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> [ 231.624477] Workqueue: kblockd blk_mq_requeue_work
> [ 231.628532] RIP: 0010:bfq_put_queue+0x10b/0x130
> [ 231.635453] RSP: 0000:ffffc90000377c98 EFLAGS: 00010282
> [ 231.638621] RAX: 0000001000000000 RBX: ffff88000cdf20f0 RCX: 0000000000000000
> [ 231.642332] RDX: 0000000000000000 RSI: ffff88000d4926d8 RDI: ffff88000cdf2120
> [ 231.647000] RBP: 000000000d4926a8 R08: 0000000000000041 R09: ffff88000cdf20f0
> [ 231.652682] R10: 0000000000105a7f R11: 000000000002000b R12: ffff88000cdf2120
> [ 231.657102] R13: ffff88000e152188 R14: 0000000000000041 R15: 0000000000000000
> [ 231.661213] FS: 0000000000000000(0000) GS:ffff88000f800000(0000) knlGS:0000000000000000
> [ 231.664746] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 231.667647] CR2: 0000001000000028 CR3: 0000000004008002 CR4: 00000000001606f0
> [ 231.671475] Call Trace:
> [ 231.673873] bfq_finish_requeue_request+0x54/0x380
> [ 231.676823] __blk_mq_requeue_request+0x5c/0x140
> [ 231.679465] blk_mq_dispatch_rq_list+0x1b4/0x4c0
> [ 231.681798] blk_mq_sched_dispatch_requests+0x105/0x190
> [ 231.685059] __blk_mq_run_hw_queue+0x80/0x90
> [ 231.687750] __blk_mq_delay_run_hw_queue+0x92/0xe0
> [ 231.691510] blk_mq_run_hw_queue+0x25/0x90
> [ 231.694759] blk_mq_run_hw_queues+0x3a/0x50
> [ 231.696706] blk_mq_requeue_work+0x116/0x140
> [ 231.699340] process_one_work+0x1df/0x420
> [ 231.703147] worker_thread+0x2b/0x3d0
> [ 231.705322] ? process_one_work+0x420/0x420
> [ 231.707002] kthread+0x113/0x130
> [ 231.708494] ? kthread_create_on_node+0x70/0x70
> [ 231.710209] ? kthread_create_on_node+0x70/0x70
> [ 231.712754] ret_from_fork+0x35/0x40
> [ 231.715068] Code: c1 e8 06 83 e0 01 48 83 f8 01 45 19 f6 e8 be 3b 00 00 41 83 e6 ee 48 89 c7 41 83 c6 53 e8 8e 3b 00 00 49 89 d9 45 89 f0 44 89 f9 <48> 8b 70 28 48 c7 c2 3a 9a e5 81 55 4c 89 ef e8 11 1c e0 ff 8b
> [ 231.725379] RIP: bfq_put_queue+0x10b/0x130 RSP: ffffc90000377c98
> [ 231.728391] CR2: 0000001000000028
> [ 231.730840] ---[ end trace 03bd81aa0d2b1434 ]---
> [ 231.733269] note: kworker/0:1H[187] exited with preempt_count 1
>
> (gdb) l *(bfq_put_queue+0x10b)
> 0xffffffff81334d1b is in bfq_put_queue (block/bfq-iosched.c:3978).
> 3973 #ifdef CONFIG_BFQ_GROUP_IOSCHED
> 3974 struct bfq_group *bfqg = bfqq_group(bfqq);
> 3975 #endif
> 3976
> 3977 if (bfqq->bfqd)
> 3978 bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d",
> 3979 bfqq, bfqq->ref);
> 3980
> 3981 bfqq->ref--;
> 3982 if (bfqq->ref)
>
> (gdb) l *(bfq_finish_requeue_request+0x54)
> 0xffffffff81335294 is in bfq_finish_requeue_request (block/bfq-iosched.c:4804).
> 4799 * that re-insertions of requeued requests, without
> 4800 * re-preparation, can happen only for pass_through or at_head
> 4801 * requests (which are not re-inserted into bfq internal
> 4802 * queues).
> 4803 */
> 4804 rq->elv.priv[0] = NULL;
> 4805 rq->elv.priv[1] = NULL;
> 4806 }
> 4807
> 4808 /*
>
> [ 322.939697] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> [ 322.944283] IP: blk_flush_complete_seq+0x206/0x300
> [ 322.947463] PGD 0 P4D 0
> [ 322.950266] Oops: 0002 [#2] PREEMPT SMP PTI
> [ 322.958898] Modules linked in: kvm_intel bochs_drm nls_iso8859_1 nls_cp437 vfat fat ttm kvm drm_kms_helper drm iTCO_wdt irqbypass psmouse ppdev iTCO_vendor_support input_leds led_class i2c_i801 intel_agp parport_pc intel_gtt joydev lpc_ich rtc_cmos agpgart evdev parport syscopyarea mousedev qemu_fw_cfg sysfillrect mac_hid sysimgblt fb_sys_fops sch_fq_codel ip_tables x_tables xfs dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio libcrc32c crc32c_generic dm_crypt algif_skcipher af_alg dm_mod hid_generic usbhid hid crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel raid10 pcbc md_mod sr_mod cdrom sd_mod serio_raw atkbd libps2 uhci_hcd xhci_pci xhci_hcd ahci ehci_pci libahci aesni_intel aes_x86_64 crypto_simd glue_helper ehci_hcd cryptd libata usbcore usb_common i8042 serio virtio_scsi
> [ 323.001668] scsi_mod virtio_blk virtio_net virtio_pci virtio_ring virtio
> [ 323.006121] CPU: 0 PID: 215 Comm: kworker/u5:1 Tainted: G D 4.15.0-pf2 #1
> [ 323.010263] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> [ 323.021225] Workqueue: kcryptd kcryptd_crypt [dm_crypt]
> [ 323.024947] RIP: 0010:blk_flush_complete_seq+0x206/0x300
> [ 323.028405] RSP: 0018:ffff88000f803ed0 EFLAGS: 00010086
> [ 323.032491] RAX: ffff88000cfe78b0 RBX: ffff88000cfe78a0 RCX: ffff88000d4d85a8
> [ 323.036262] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88000d4d8500
> [ 323.041032] RBP: ffff88000d6510a0 R08: ffff88000cfe78a0 R09: 0000000000000000
> [ 323.051518] R10: ffff88000dab4d00 R11: ffffffffc01aafb0 R12: 0000000000000000
> [ 323.055818] R13: ffff88000cfe78f0 R14: 0000000000000046 R15: ffff88000cfe78a0
> [ 323.060965] FS: 0000000000000000(0000) GS:ffff88000f800000(0000) knlGS:0000000000000000
> [ 323.065902] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 323.070571] CR2: 0000000000000008 CR3: 0000000004008001 CR4: 00000000001606f0
> [ 323.076591] Call Trace:
> [ 323.081685] <IRQ>
> [ 323.084025] mq_flush_data_end_io+0xb3/0xf0
> [ 323.087155] scsi_end_request+0x90/0x1e0 [scsi_mod]
> [ 323.095768] scsi_io_completion+0x237/0x650 [scsi_mod]
> [ 323.099928] flush_smp_call_function_queue+0x7c/0xf0
> [ 323.104028] smp_call_function_single_interrupt+0x32/0xf0
> [ 323.114170] call_function_single_interrupt+0xa2/0xb0
> [ 323.118208] </IRQ>
> [ 323.121040] RIP: 0010:_aesni_enc4+0x178/0x190 [aesni_intel]
> [ 323.124658] RSP: 0018:ffffc900004a7c40 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff04
> [ 323.128777] RAX: ffffffffc01ab208 RBX: 0000000000000180 RCX: 0000000000000000
> [ 323.133003] RDX: ffff88000daf9c80 RSI: ffff88000a2b3c80 RDI: ffff88000cd24260
> [ 323.139211] RBP: ffffc900004a7d40 R08: ffff8800089f7718 R09: 0000000000000010
> [ 323.146930] R10: ffff88000cd24290 R11: ffffffffc01aafb0 R12: 0000000000000080
> [ 323.151758] R13: ffffffffc01c90c8 R14: ffff88000a2b3d00 R15: ffff88000daf9d00
> [ 323.156507] ? _aesni_enc1+0xac/0xac [aesni_intel]
> [ 323.160419] ? _aesni_dec1+0xac/0xac [aesni_intel]
> [ 323.164204] ? aesni_xts_crypt8+0x21e/0x260 [aesni_intel]
> [ 323.167322] ? glue_xts_req_128bit+0x125/0x1d0 [glue_helper]
> [ 323.178383] ? crypt_convert+0x961/0xef0 [dm_crypt]
> [ 323.182089] ? xts_decrypt+0x40/0x40 [aesni_intel]
> [ 323.185825] ? crypt_convert+0x961/0xef0 [dm_crypt]
> [ 323.189438] ? bio_alloc_bioset+0x132/0x1e0
> [ 323.191926] ? kcryptd_crypt+0x1ff/0x360 [dm_crypt]
> [ 323.194998] ? process_one_work+0x1df/0x420
> [ 323.197475] ? worker_thread+0x2b/0x3d0
> [ 323.206991] ? process_one_work+0x420/0x420
> [ 323.210387] ? kthread+0x113/0x130
> [ 323.213396] ? kthread_create_on_node+0x70/0x70
> [ 323.216751] ? ret_from_fork+0x35/0x40
> [ 323.220815] Code: 48 8b 10 48 39 d0 0f 84 8f 00 00 00 48 8b 97 b0 00 00 00 49 c1 e0 04 45 31 e4 48 8b b7 a8 00 00 00 49 01 d8 48 8d 8f a8 00 00 00 <48> 89 56 08 48 89 32 49 8b 50 18 49 89 48 18 48 89 87 a8 00 00
> [ 323.233543] RIP: blk_flush_complete_seq+0x206/0x300 RSP: ffff88000f803ed0
> [ 323.238885] CR2: 0000000000000008
> [ 323.241673] ---[ end trace 2ec7b63c3a4a4a02 ]---
> [ 323.245006] Kernel panic - not syncing: Fatal exception in interrupt
> [ 323.248858] Kernel Offset: disabled
> [ 323.250753] ---[ end Kernel panic - not syncing: Fatal exception in interrupt
>
> (gdb) l *(blk_flush_complete_seq+0x206)
> 0xffffffff813056c6 is in blk_flush_complete_seq (./include/linux/list.h:105).
> 100 * This is only for internal list manipulation where we know
> 101 * the prev/next entries already!
> 102 */
> 103 static inline void __list_del(struct list_head * prev, struct list_head * next)
> 104 {
> 105 next->prev = prev;
> 106 WRITE_ONCE(prev->next, next);
> 107 }
> 108
> 109 /**


Thank you very much Oleksandr, and Holger, for your listings,
I've managed to make a crash happen, unfortunately only after a lot of
time and I/O. Unfortunately, the crash happened for one of the call
chains not including bfq. If you guys have found a way to get these
crashes more or less easily, then I think I'll need your help here.
The first piece of information I need is whether this failure happens
even without "BFQ hierarchical scheduling support". If it does, then
the area of investigation narrows a little. So, could you please
retry after disabling hierarchical support?

Thanks,
Paolo

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