FYI, we noticed the below changes on

git://git.infradead.org/users/kbusch/linux-nvme master
commit 26efb85d35c71bc297e22773928062c97e41a8a2 ("blk-mq: dynamic h/w context count")


+------------------------------------------------+------------+------------+
|                                                | e56dda0be8 | 26efb85d35 |
+------------------------------------------------+------------+------------+
| boot_successes                                 | 6          | 2          |
| boot_failures                                  | 1          | 28         |
| WARNING:at_kernel/trace/ftrace.c:#ftrace_bug() | 1          |            |
| backtrace:perf_ftrace_event_register           | 1          |            |
| backtrace:perf_trace_init                      | 1          |            |
| backtrace:perf_tp_event_init                   | 1          |            |
| backtrace:perf_try_init_event                  | 1          |            |
| backtrace:SYSC_perf_event_open                 | 1          |            |
| backtrace:SyS_perf_event_open                  | 1          |            |
| INFO:trying_to_register_non-static_key         | 0          | 28         |
| backtrace:do_mount                             | 0          | 28         |
| backtrace:compat_SyS_mount                     | 0          | 5          |
| backtrace:SyS_mount                            | 0          | 23         |
+------------------------------------------------+------------+------------+



[   22.943488] FAT-fs (nbd10): unable to read boot sector
[   22.944820] block nbd10: Attempted send on closed socket
[   22.947117] block nbd0: Attempted send on closed socket
[   22.949310] INFO: trying to register non-static key.
[   22.950428] the code is fine but needs lockdep annotation.
[   22.951599] turning off the locking correctness validator.
[   22.952839] CPU: 0 PID: 839 Comm: mount Not tainted 4.4.0-rc2-00145-g26efb85 #1
[   22.954689] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[   22.956860]  0000000000000000 ffff88001dc43928 ffffffff8173d271 0000000000000000
[   22.958925]  ffff88001dc43990 ffffffff81112bf7 ffff88001ef21a40 0000000000000000
[   22.960946]  0000000000000002 0000000000000337 000000001ef211c0 ffff88001dc43a20
[   22.963064] Call Trace:
[   22.963926]  [<ffffffff8173d271>] dump_stack+0x4b/0x63
[   22.965115]  [<ffffffff81112bf7>] register_lock_class+0x142/0x2e9
[   22.966424]  [<ffffffff81115116>] __lock_acquire+0x179/0xdee
[   22.967700]  [<ffffffff8171cabf>] ? blk_insert_flush+0x16e/0x1b1
[   22.969038]  [<ffffffff81092028>] ? kvm_clock_read+0x25/0x2e
[   22.970322]  [<ffffffff81116121>] lock_acquire+0x10a/0x196
[   22.971538]  [<ffffffff81116352>] ? lock_release+0x1a5/0x41a
[   22.972787]  [<ffffffff81116121>] ? lock_acquire+0x10a/0x196
[   22.974085]  [<ffffffff8171cabf>] ? blk_insert_flush+0x16e/0x1b1
[   22.975427]  [<ffffffff82e137df>] _raw_spin_lock_irq+0x3f/0x75
[   22.976684]  [<ffffffff8171cabf>] ? blk_insert_flush+0x16e/0x1b1
[   22.978001]  [<ffffffff8171cabf>] blk_insert_flush+0x16e/0x1b1
[   22.979303]  [<ffffffff81723fec>] blk_sq_make_request+0xf8/0x19f
[   22.980610]  [<ffffffff81719667>] generic_make_request+0xbd/0x160
[   22.981909]  [<ffffffff817197ff>] submit_bio+0xf5/0x100
[   22.983063]  [<ffffffff8110c29f>] ? __init_waitqueue_head+0x3b/0x4e
[   22.984365]  [<ffffffff817117f3>] submit_bio_wait+0x54/0x6a
[   22.985581]  [<ffffffff8171c3f4>] blkdev_issue_flush+0x62/0x84
[   22.986866]  [<ffffffff814d6d5b>] xfs_blkdev_issue_flush+0x19/0x1b
[   22.988197]  [<ffffffff814be9b0>] xfs_free_buftarg+0x3a/0x47
[   22.989396]  [<ffffffff814d559d>] xfs_close_devices+0x64/0x69
[   22.990588]  [<ffffffff814d665c>] xfs_fs_fill_super+0x323/0x504
[   22.991795]  [<ffffffff81201851>] mount_bdev+0x148/0x19f
[   22.992905]  [<ffffffff814d6339>] ? xfs_parseargs+0x8b6/0x8b6
[   22.994062]  [<ffffffff81112e61>] ? lockdep_init_map+0xc3/0x1c6
[   22.995245]  [<ffffffff814d4bf6>] xfs_fs_mount+0x15/0x17
[   22.996324]  [<ffffffff8120228c>] mount_fs+0x67/0x131
[   22.997362]  [<ffffffff8121921e>] vfs_kern_mount+0x6c/0xde
[   22.998495]  [<ffffffff8121bc35>] do_mount+0x88f/0x9ce
[   22.999574]  [<ffffffff811bf0f5>] ? strndup_user+0x3f/0x8c
[   23.000706]  [<ffffffff81241967>] compat_SyS_mount+0x185/0x1b1
[   23.001892]  [<ffffffff81003b19>] do_syscall_32_irqs_off+0x5c/0x6b
[   23.003119]  [<ffffffff82e169e8>] entry_INT80_compat+0x38/0x50
[   23.004882] SQUASHFS error: squashfs_read_data failed to read block 0x0
[   23.006257] squashfs: SQUASHFS error: unable to read squashfs_super_block


Thanks,
Ying Huang