Hi Jens and Dennis, Just found the following issue when testing for-4.21/block when running stress io & device remove on scsi_debug, and it should be caused by recent blkcg changes. [ 37.144330] sd 8:0:0:15: [sds] Synchronizing SCSI cache [ 37.665644] BUG: unable to handle kernel NULL pointer dereference at 0000000000000048 [ 37.674748] PGD 8000000269c3b067 P4D 8000000269c3b067 PUD 269c3c067 PMD 0 [ 37.675703] Oops: 0000 [#1] PREEMPT SMP PTI [ 37.676294] CPU: 2 PID: 1270 Comm: fio Not tainted 4.20.0-rc6_f0ea84586b7c_for-next+ #1 [ 37.677392] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014 [ 37.678563] RIP: 0010:__bio_associate_blkg+0x1e/0x81 [ 37.679255] Code: 00 00 5b 5d c3 0f 1f 44 00 00 eb 94 0f 1f 44 00 00 41 54 55 48 89 fd 53 48 89 f3 e8 80 ff ff ff bf 01 00 00 00 e8 94 37 d7 ff <48> 8b 43 48 a8 03 74 06 48 8b 53 40 eb 1b 65 48 ff 00 41 b4 01 eb [ 37.681801] RSP: 0018:ffffc9000169bb80 EFLAGS: 00010246 [ 37.682525] RAX: ffff888269c40000 RBX: 0000000000000000 RCX: 0000000000000000 [ 37.683506] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8132c44f [ 37.684486] RBP: ffff888270fecb18 R08: 000000000000001e R09: ffffffffffffffff [ 37.685473] R10: 00000000ffffffca R11: 0000000000000000 R12: ffff88826630b758 [ 37.686450] R13: ffff888270fecb18 R14: ffff888107811118 R15: ffff888270fecb18 [ 37.687435] FS: 00007f7d486c6ec0(0000) GS:ffff888277b00000(0000) knlGS:0000000000000000 [ 37.688548] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 37.689345] CR2: 0000000000000048 CR3: 0000000269c4a001 CR4: 0000000000760ee0 [ 37.690333] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 37.691330] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 37.692320] PKRU: 55555554 [ 37.692704] Call Trace: [ 37.693070] bio_associate_blkg_from_css+0x4e/0x57 [ 37.693734] bio_associate_blkg+0x4d/0x53 [ 37.694300] blkdev_direct_IO+0x1d4/0x3c9 [ 37.694861] ? __switch_to_asm+0x34/0x70 [ 37.695417] ? aio_complete+0x2cc/0x2cc [ 37.695962] ? __switch_to_asm+0x34/0x70 [ 37.696511] ? __switch_to_asm+0x40/0x70 [ 37.697066] ? __switch_to_asm+0x34/0x70 [ 37.697614] ? __switch_to_asm+0x40/0x70 [ 37.698166] ? __switch_to_asm+0x34/0x70 [ 37.698717] ? generic_file_read_iter+0x96/0x110 [ 37.699366] generic_file_read_iter+0x96/0x110 [ 37.699991] aio_read+0xe9/0x178 [ 37.700448] ? __switch_to_asm+0x34/0x70 [ 37.701004] ? __switch_to_asm+0x34/0x70 [ 37.701552] ? __switch_to_asm+0x40/0x70 [ 37.702109] ? __switch_to_asm+0x34/0x70 [ 37.702659] ? __switch_to_asm+0x40/0x70 [ 37.703214] ? __switch_to_asm+0x34/0x70 [ 37.703762] ? __switch_to_asm+0x40/0x70 [ 37.704317] ? __switch_to_asm+0x34/0x70 [ 37.704867] ? __switch_to_asm+0x40/0x70 [ 37.705423] ? __switch_to_asm+0x34/0x70 [ 37.705973] ? __switch_to_asm+0x40/0x70 [ 37.706523] ? __switch_to_asm+0x34/0x70 [ 37.707088] ? io_submit_one+0x2e1/0x67b [ 37.707638] io_submit_one+0x2e1/0x67b [ 37.708171] ? __se_sys_io_submit+0xc5/0x15e [ 37.708770] __se_sys_io_submit+0xc5/0x15e [ 37.709348] ? 0xffffffff81000000 [ 37.709819] ? do_syscall_64+0x84/0x13f [ 37.710362] ? __se_sys_io_submit+0x15e/0x15e [ 37.710987] do_syscall_64+0x84/0x13f [ 37.711505] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 37.712216] RIP: 0033:0x7f7d471c6687 [ 37.712720] Code: 00 00 00 49 83 38 00 75 ed 49 83 78 08 00 75 e6 8b 47 0c 39 47 08 75 de 31 c0 c3 0f 1f 84 00 00 00 00 00 b8 d1 00 00 00 0f 05 <c3> 0f 1f 84 00 00 00 00 00 b8 d2 00 00 00 0f 05 c3 0f 1f 84 00 00 [ 37.715280] RSP: 002b:00007ffcb7d448c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000d1 [ 37.716314] RAX: ffffffffffffffda RBX: 00007f7d22e90298 RCX: 00007f7d471c6687 [ 37.717297] RDX: 00000000009f4b20 RSI: 0000000000000001 RDI: 00007f7d484ea000 [ 37.718280] RBP: 0000000000003e70 R08: 0000000000000001 R09: 00000000008799e0 [ 37.719264] R10: 0000000000000000 R11: 0000000000000202 R12: 00007f7d22e90298 [ 37.720249] R13: 0000000000000000 R14: 00000000009f4cc0 R15: 00000000009e0c60 [ 37.721232] Modules linked in: scsi_debug isofs iTCO_wdt i2c_i801 i2c_core iTCO_vendor_support lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel qemu_fw_cfg virtio_scsi dm_mirror dm_region_hash dm_log dm_mod [ 37.724240] Dumping ftrace buffer: [ 37.724717] (ftrace buffer empty) [ 37.725223] CR2: 0000000000000048 [ 37.725692] ---[ end trace 4758725073447b42 ]--- Thanks, Ming Lei
