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SubjectRe: [PATCH BUGFIX 1/1] block, bfq: add requeue-request hook
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 /**

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