On Mon, Nov 26, 2018 at 10:33:32AM -0700, Jens Axboe wrote:

On 11/26/18 9:54 AM, Keith Busch wrote:

quoted

The iterative update to the previous version taking into account review
comments.

Background:

The main objective is to remove the generic block layer's lock prefix
currently required to transition a request to its completed state by
shifting that expense to lower level drivers that actually need it,
and removing the software layering violation that was required to use
that mechnaism.

Thanks Keith, added for 4.21.

Hi Jens & Keith,

Seems this patchset causes the following kernel panic, since not see
this issue with commit 4ab32bf3305e

[ 1478.366776] nvmet: adding nsid 1 to subsystem testnqn
[ 1478.385104] nvmet: creating controller 1 for subsystem testnqn for NQN nqn.2014-08.org.nvmexpress:uuid:8786b40e-ed54-4f9e-b1b0-6507377ffa97.
[ 1478.386975] nvme nvme1: creating 4 I/O queues.
[ 1478.388784] nvme nvme1: new ctrl: "testnqn"
[ 1479.396523] nvme io: runtime 40
[ 1575.259358] nvme reset: runtime 40
[ 1575.263920] nvme nvme0: resetting controller
[ 1575.288473] nvme nvme0: 4/0/0 read/write/poll queues
[ 1575.291531] nvme nvme1: resetting controller
[ 1575.298338] print_req_error: I/O error, dev nvme1n1, sector 524287272
[ 1575.299169] print_req_error: I/O error, dev nvme1n1, sector 524287328
[ 1575.299950] BUG: unable to handle kernel NULL pointer dereference at 0000000000000198
[ 1575.299951] PGD 0 P4D 0 
[ 1575.299954] Oops: 0002 [#1] PREEMPT SMP PTI
[ 1575.299972] CPU: 0 PID: 12014 Comm: kworker/u8:0 Not tainted 4.20.0-rc3_5f0ed774ed29_for-next+ #1
[ 1575.299973] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-2.fc27 04/01/2014
[ 1575.299978] Workqueue: nvme-reset-wq nvme_loop_reset_ctrl_work [nvme_loop]
[ 1575.299985] RIP: 0010:blk_mq_free_request+0x7e/0xe4
[ 1575.299987] Code: 00 00 00 00 00 8b 53 18 b8 01 00 00 00 84 d2 74 0b 31 c0 81 e2 00 08 06 00 0f 95 c0 49 ff 84 c5 80 00 00 00 f6 43 1c 40 74 09 <f0> 41 ff 8c 24 98 01 00 00 83 3d 0b c6 52 01 00 74 15 0f b6 43 18
[ 1575.299988] RSP: 0018:ffff888277a03e48 EFLAGS: 00010002
[ 1575.299989] RAX: 0000000000000001 RBX: ffff88823aa04e00 RCX: ffff888265e71dc0
[ 1575.299990] RDX: 0000000000080700 RSI: ffff888265e71c00 RDI: ffff88821d822808
[ 1575.299991] RBP: ffff888267a3d750 R08: 00000000ffffffff R09: ffff888265e71dd0
[ 1575.299992] R10: ffff888265e71dd0 R11: 0000000000000020 R12: 0000000000000000
[ 1575.299993] R13: ffffe8ffffc0be40 R14: 0000000000000000 R15: 0000000000006000
[ 1575.299994] FS:  0000000000000000(0000) GS:ffff888277a00000(0000) knlGS:0000000000000000
[ 1575.299995] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1575.299996] CR2: 0000000000000198 CR3: 0000000236de8005 CR4: 0000000000760ef0
[ 1575.300000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1575.300001] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1575.300001] PKRU: 55555554
[ 1575.300002] Call Trace:
[ 1575.300012]  <IRQ>
[ 1575.300016]  blk_mq_complete_request+0xda/0xfd
[ 1575.300021]  nvmet_req_complete+0x11/0x5e [nvmet]
[ 1575.300025]  nvmet_bio_done+0x2b/0x3d [nvmet]
[ 1575.300027]  blk_update_request+0x177/0x27b
[ 1575.300032]  ? null_complete_rq+0x11/0x11 [null_blk]
[ 1575.300034]  blk_mq_end_request+0x1a/0xc8
[ 1575.300036]  null_cmd_timer_expired+0xe/0x11 [null_blk]
[ 1575.300040]  __hrtimer_run_queues+0x176/0x238
[ 1575.300043]  ? kvm_clock_read+0x14/0x23
[ 1575.300045]  hrtimer_interrupt+0x103/0x21c
[ 1575.300049]  smp_apic_timer_interrupt+0xd3/0x141
[ 1575.300051]  apic_timer_interrupt+0xf/0x20
[ 1575.300053]  </IRQ>
[ 1575.300055] RIP: 0010:console_unlock+0x3a8/0x45f
[ 1575.300057] Code: 59 00 8a 1d bc 0e 5d 01 48 c7 c7 f0 0c 6a 82 4c 89 2d b6 0e 5d 01 e8 fe c0 59 00 84 db 75 15 e8 9f 1c 00 00 48 8b 3c 24 57 9d <0f> 1f 44 00 00 e9 aa fc ff ff c6 05 89 0e 5d 01 00 e8 83 1c 00 00
[ 1575.300057] RSP: 0018:ffffc90003a3fc20 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
[ 1575.300059] RAX: 0000000080000002 RBX: 0000000000000000 RCX: 0000000000000000
[ 1575.300060] RDX: 0000000000000001 RSI: 0000000000000046 RDI: 0000000000000246
[ 1575.300060] RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
[ 1575.300061] R10: 0000000005f5e100 R11: ffffffff826a00e7 R12: ffffffff821e7460
[ 1575.300062] R13: 0000000000000000 R14: ffffffff826a00e0 R15: 0000000000000000
[ 1575.300067]  vprintk_emit+0x1ff/0x236
[ 1575.300069]  printk+0x52/0x6e
[ 1575.300071]  blk_update_request+0x10a/0x27b
[ 1575.300074]  blk_mq_end_request+0x1a/0xc8
[ 1575.300076]  blk_mq_complete_request+0xda/0xfd
[ 1575.300080]  nvme_cancel_request+0x5b/0x60
[ 1575.300082]  bt_tags_for_each+0xe2/0x10c
[ 1575.300085]  ? nvme_complete_rq+0x162/0x162
[ 1575.300087]  ? nvme_complete_rq+0x162/0x162
[ 1575.300089]  blk_mq_tagset_busy_iter+0x68/0x75
[ 1575.300091]  nvme_loop_shutdown_ctrl+0x38/0x86 [nvme_loop]
[ 1575.300094]  nvme_loop_reset_ctrl_work+0x2a/0xcf [nvme_loop]
[ 1575.300098]  process_one_work+0x1da/0x313
[ 1575.300101]  ? rescuer_thread+0x282/0x282
[ 1575.300103]  process_scheduled_works+0x27/0x2c
[ 1575.300105]  worker_thread+0x1e7/0x295
[ 1575.300107]  kthread+0x115/0x11d
[ 1575.300109]  ? kthread_park+0x76/0x76
[ 1575.300111]  ret_from_fork+0x35/0x40
[ 1575.300113] Modules linked in: nvme_loop nvmet nvme_fabrics null_blk scsi_debug xfs libcrc32c isofs iTCO_wdt iTCO_vendor_support i2c_i801 i2c_core lpc_ich mfd_core ip_tables sr_mod cdrom usb_storage sd_mod ahci libahci libata crc32c_intel virtio_scsi qemu_fw_cfg dm_mirror dm_region_hash dm_log dm_mod [last unloaded: null_blk]
[ 1575.300127] Dumping ftrace buffer:
[ 1575.300129]    (ftrace buffer empty)
[ 1575.300130] CR2: 0000000000000198
[ 1575.300133] ---[ end trace f941476562612d99 ]---

thanks,
Ming