[powerpc][next-20210625] WARN block/mq-deadline-main.c:743 during boot

[Sachin Sant]

While booting 5.13.0-rc7-next-20210625 on POWER9 LPAR following warning
is seen:

[    3.111826] device-mapper: multipath service-time: version 0.3.0 loaded
[    3.485799] ------------[ cut here ]------------
[    3.485809] WARNING: CPU: 9 PID: 225 at block/mq-deadline-main.c:743 dd_insert_requests+0x460/0x4a0
[    3.485819] Modules linked in: dm_service_time sd_mod t10_pi sg ibmvfc scsi_transport_fc ibmveth dm_multipath dm_mirror dm_region_hash dm_log dm_mod fuse
[    3.485836] CPU: 9 PID: 225 Comm: kworker/9:1H Not tainted 5.13.0-rc7-next-20210625 #3
[    3.485842] Workqueue: kblockd blk_mq_requeue_work
[    3.485848] NIP:  c0000000006a5c20 LR: c0000000006a5958 CTR: c0000000006a57c0
[    3.485852] REGS: c000000009d2f800 TRAP: 0700   Not tainted  (5.13.0-rc7-next-20210625)
[    3.485857] MSR:  800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 24004828  XER: 00000001
[    3.485871] CFAR: c0000000006a5964 IRQMASK: 0 
[    3.485871] GPR00: c0000000006a5920 c000000009d2faa0 c000000001adb700 0000000000000000 
[    3.485871] GPR04: c000000028750048 c000000028750048 0000000000000000 c000000028750048 
[    3.485871] GPR08: 0000000000000020 c000000009530400 0000000000000024 0000000000000007 
[    3.485871] GPR12: 0000000000002000 c00000001ec53280 c00000000018bb48 c000000009530400 
[    3.485871] GPR16: 0000000000000000 c000000028750000 0000000c00002204 c00000000d77512c 
[    3.485871] GPR20: c00000000d775000 000000000004001a c000000000d96928 c00000002ea4e400 
[    3.485871] GPR24: c00000002e190000 0000000000000003 c000000009d2fb98 c000000009d2fac8 
[    3.485871] GPR28: c00000000d775000 0000000000000001 0000000000080700 c000000028750048 
[    3.485925] NIP [c0000000006a5c20] dd_insert_requests+0x460/0x4a0
[    3.485930] LR [c0000000006a5958] dd_insert_requests+0x198/0x4a0
[    3.485935] Call Trace:
[    3.485937] [c000000009d2faa0] [c00000000001e528] __switch_to+0x2c8/0x480 (unreliable)
[    3.485945] [c000000009d2fb70] [c00000000068550c] blk_mq_sched_insert_request+0xfc/0x210
[    3.485951] [c000000009d2fbf0] [c00000000067d314] blk_mq_requeue_work+0x174/0x250
[    3.485958] [c000000009d2fc60] [c00000000017f634] process_one_work+0x264/0x540
[    3.485964] [c000000009d2fd00] [c00000000017f998] worker_thread+0x88/0x630
[    3.485970] [c000000009d2fda0] [c00000000018bcd4] kthread+0x194/0x1a0
[    3.485976] [c000000009d2fe10] [c00000000000c750] ret_from_kernel_thread+0x5c/0x6c
[    3.485983] Instruction dump:
[    3.485986] 7ea94838 2f890000 409eff64 7e248b78 7f03c378 4bfbd0dd 60000000 e9380000 
[    3.485996] 2fa90000 409eff48 fa380000 4bffff40 <0fe00000> 4bfffd44 60000000 60000000 
[    3.486005] ---[ end trace 42319989f7cb8ff4 ]---
[  OK  ] Found device /dev/disk/by-uuid/186c6f84-531c-4570-89cc-6490f20090e9.

Last known tested & working build was 5.13.0-rc6-next-20210618.

This problem seems to be introduced with

commit 08a9ad8bf60738
       block/mq-deadline: Add cgroup support

Reverting this patch allows the kernel to boot without the mentioned warning.

Have attached the boot log. IOSCHED_DEADLINE is set to yes.

CONFIG_MQ_IOSCHED_DEADLINE=y
CONFIG_MQ_IOSCHED_KYBER=y
# CONFIG_IOSCHED_BFQ is not set
# end of IO Schedulers

Thanks
-Sachin

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