FYI, we noticed the following commit (built with gcc-7):

commit: 48d9b0d43105e0da2b7c135eedd24e51234fb5e4 ("block: account statistics for passthrough requests")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

in testcase: rcuperf
with following parameters:

	runtime: 300s
	perf_type: tasks



on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+-------------------------------------------------------+------------+------------+
|                                                       | 8148f0b564 | 48d9b0d431 |
+-------------------------------------------------------+------------+------------+
| boot_successes                                        | 8          | 0          |
| boot_failures                                         | 0          | 8          |
| BUG:kernel_NULL_pointer_dereference,address           | 0          | 8          |
| Oops:#[##]                                            | 0          | 8          |
| EIP:blk_account_io_completion                         | 0          | 8          |
| EIP:ide_output_data                                   | 0          | 8          |
| Kernel_panic-not_syncing:Fatal_exception_in_interrupt | 0          | 8          |
+-------------------------------------------------------+------------+------------+


If you fix the issue, kindly add following tag
Reported-by: kernel test robot <rong.a.chen@intel.com>


[   14.392111] BUG: kernel NULL pointer dereference, address: 000002ac
[   14.392607] #PF: supervisor write access in kernel mode
[   14.392607] #PF: error_code(0x0002) - not-present page
[   14.392607] *pde = 00000000 
[   14.392607] Oops: 0002 [#1]
[   14.392607] CPU: 0 PID: 237 Comm: kworker/0:1H Not tainted 5.4.0-rc2-00011-g48d9b0d43105e #1
[   14.392607] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   14.392607] Workqueue: kblockd drive_rq_insert_work
[   14.392607] EIP: blk_account_io_completion+0x7a/0xf0
[   14.392607] Code: 89 54 24 08 31 d2 89 4c 24 04 31 c9 c7 04 24 02 00 00 00 c1 ee 09 e8 f5 21 a6 ff e8 70 5c a7 ff 8b 53 60 8d 04 bd 00 00 00 00 <01> b4 02 ac 02 00 00 8b 9a 88 02 00 00 85 db 74 11 85 d2 74 51 8b
[   14.392607] EAX: 00000000 EBX: f5b80000 ECX: 00000000 EDX: 00000000
[   14.392607] ESI: 00000000 EDI: 00000000 EBP: f3031e70 ESP: f3031e54
[   14.392607] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010046
[   14.392607] CR0: 80050033 CR2: 000002ac CR3: 03c25000 CR4: 000406d0
[   14.392607] Call Trace:
[   14.392607]  <IRQ>
[   14.392607]  ? blk_account_io_completion+0x38/0xf0
[   14.392607]  blk_update_request+0x85/0x420
[   14.392607]  ? _raw_spin_unlock_irqrestore+0x4f/0x60
[   14.392607]  ? trace_hardirqs_off+0xca/0xe0
[   14.392607]  ? _raw_spin_unlock_irqrestore+0x4f/0x60
[   14.392607]  ? complete+0x41/0x50
[   14.392607]  ide_end_rq+0x38/0xa0
[   14.392607]  ide_complete_rq+0x3d/0x70
[   14.392607]  cdrom_newpc_intr+0x258/0xba0
[   14.392607]  ? find_held_lock+0x2f/0xa0
[   14.392607]  ? cdrom_analyze_sense_data+0x1b0/0x1b0
[   14.392607]  ide_intr+0x135/0x250
[   14.392607]  __handle_irq_event_percpu+0x3e/0x250
[   14.392607]  handle_irq_event_percpu+0x1f/0x50
[   14.392607]  handle_irq_event+0x32/0x60
[   14.392607]  ? handle_fasteoi_irq+0x160/0x160
[   14.392607]  handle_level_irq+0x6c/0x110
[   14.392607]  handle_irq+0x72/0xa0
[   14.392607]  </IRQ>
[   14.392607]  do_IRQ+0x45/0xad
[   14.392607]  common_interrupt+0x115/0x11c
[   14.392607] EIP: ide_output_data+0xb7/0x140
[   14.392607] Code: 00 00 00 0f b7 03 66 89 07 83 c3 02 39 d3 75 f3 83 c4 14 5b 5e 5f 5d c3 8d 76 00 8b 4d ec d1 e9 80 7d f0 00 75 15 89 de 89 fa <f3> 66 6f 83 c4 14 5b 5e 5f 5d c3 8d b6 00 00 00 00 85 c9 74 ee 49
[   14.392607] EAX: 00000000 EBX: f5b800ac ECX: 00000000 EDX: 00000170
[   14.392607] ESI: f5b800b8 EDI: 00000170 EBP: f6a57dac ESP: f6a57d8c
[   14.392607] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010246
[   14.392607]  ? print_usage_bug+0x9b/0x1f0
[   14.392607]  ? ide_output_data+0xb7/0x140
[   14.392607]  ? ide_set_handler+0x42/0x50
[   14.392607]  ide_transfer_pc+0x11c/0x2a0
[   14.392607]  ? ide_check_atapi_device+0x130/0x130
[   14.392607]  ? ide_pc_intr+0x3d0/0x3d0
[   14.392607]  ide_issue_pc+0x160/0x250
[   14.392607]  ? ide_check_atapi_device+0x130/0x130
[   14.392607]  ide_cd_do_request+0x18e/0x3d0
[   14.392607]  ide_issue_rq+0x13a/0x6a0
[   14.392607]  ? _raw_spin_unlock_irq+0x22/0x30
[   14.392607]  ? lockdep_hardirqs_on+0xe4/0x190
[   14.392607]  ? _raw_spin_unlock_irq+0x22/0x30
[   14.392607]  ? trace_hardirqs_on+0x38/0xe0
[   14.392607]  ? drive_rq_insert_work+0x7a/0xf0
[   14.392607]  drive_rq_insert_work+0x8a/0xf0
[   14.392607]  process_one_work+0x207/0x500
[   14.392607]  ? process_one_work+0x16b/0x500
[   14.392607]  worker_thread+0x39/0x400
[   14.392607]  kthread+0xee/0x110
[   14.392607]  ? process_one_work+0x500/0x500
[   14.392607]  ? kthread_create_on_node+0x30/0x30
[   14.392607]  ret_from_fork+0x1e/0x28
[   14.392607] Modules linked in:
[   14.392607] CR2: 00000000000002ac
[   14.392607] ---[ end trace 2efe0b990b41cd59 ]---


To reproduce:

        # build kernel
	cd linux
	cp config-5.4.0-rc2-00011-g48d9b0d43105e .config
	make HOSTCC=gcc-7 CC=gcc-7 ARCH=i386 olddefconfig prepare modules_prepare bzImage

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email



Thanks,
Rong Chen