Re: [PATCH] bsg: convert to use blk-mq

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On 10/22/18 4:03 AM, Benjamin Block wrote:
> On Fri, Oct 19, 2018 at 09:50:53AM -0600, Jens Axboe wrote:
>> On 10/19/18 9:01 AM, Benjamin Block wrote:
>>> On Wed, Oct 17, 2018 at 10:01:16AM -0600, Jens Axboe wrote:
>>>> On 10/17/18 9:55 AM, Benjamin Block wrote:
>>>>> On Tue, Oct 16, 2018 at 08:43:01AM -0600, Jens Axboe wrote:
>>>>>> Requires a few changes to the FC transport class as well.
>>>>>>
>>>>>> Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
>>>>>> Cc: Benjamin Block <bblock@xxxxxxxxxxxxxxxxxx>
>>>>>> Cc: linux-scsi@xxxxxxxxxxxxxxx
>>>>>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>>>>>> ---
>>>>>>  block/bsg-lib.c                  | 102 +++++++++++++++++--------------
>>>>>>  drivers/scsi/scsi_transport_fc.c |  61 ++++++++++--------
>>>>>>  2 files changed, 91 insertions(+), 72 deletions(-)
>>>>>>
>>
>> but that's not going to apply cleanly... Can you just try and run my
>> mq-conversions branch? That has everything, and it also has that
>> alloc failure fixed.
>>
>> git://git.kernel.dk/linux-block mq-conversions
>>
> 
> Ok so, that gets past the stage where we initialize the queues. Simple
> SCSI-I/O also seems to work, that is for example an INQUIRY(10), but
> transport commands that get passed to the driver break. Tried to send
> a FibreChannel GPN_FT (remote port discovery).
> 
> As the BSG interface goes. This is a bidirectional command, that has
> both a buffer for the request and for the reply. AFAIR BSG will create a
> struct request for each of them. Protocol is BSG_PROTOCOL_SCSI,
> Subprotocol BSG_SUB_PROTOCOL_SCSI_TRANSPORT. The rest should be
> transparent till we get into the driver.
> 
> First got this:
> 
> [  566.531100] BUG: sleeping function called from invalid context at mm/slab.h:421
> [  566.531452] in_atomic(): 1, irqs_disabled(): 0, pid: 3104, name: bsg_api_test
> [  566.531460] 1 lock held by bsg_api_test/3104:
> [  566.531466]  #0: 00000000cb4b58e8 (rcu_read_lock){....}, at: hctx_lock+0x30/0x118
> [  566.531498] Preemption disabled at:
> [  566.531503] [<00000000008175d0>] __blk_mq_delay_run_hw_queue+0x50/0x218
> [  566.531519] CPU: 3 PID: 3104 Comm: bsg_api_test Tainted: G        W         4.19.0-rc6-bb-next+ #1
> [  566.531527] Hardware name: IBM 3906 M03 704 (LPAR)
> [  566.531533] Call Trace:
> [  566.531544] ([<00000000001167fa>] show_stack+0x8a/0xd8)
> [  566.531555]  [<0000000000bcc6d2>] dump_stack+0x9a/0xd8
> [  566.531565]  [<0000000000196410>] ___might_sleep+0x280/0x298
> [  566.531576]  [<00000000003e528c>] __kmalloc+0xbc/0x560
> [  566.531584]  [<000000000083186a>] bsg_map_buffer+0x5a/0xb0
> [  566.531591]  [<0000000000831948>] bsg_queue_rq+0x88/0x118
> [  566.531599]  [<000000000081ab56>] blk_mq_dispatch_rq_list+0x37e/0x670
> [  566.531607]  [<000000000082050e>] blk_mq_do_dispatch_sched+0x11e/0x130
> [  566.531615]  [<0000000000820dfe>] blk_mq_sched_dispatch_requests+0x156/0x1a0
> [  566.531622]  [<0000000000817564>] __blk_mq_run_hw_queue+0x144/0x160
> [  566.531630]  [<0000000000817614>] __blk_mq_delay_run_hw_queue+0x94/0x218
> [  566.531638]  [<00000000008178b2>] blk_mq_run_hw_queue+0xda/0xf0
> [  566.531645]  [<00000000008211d8>] blk_mq_sched_insert_request+0x1a8/0x1e8
> [  566.531653]  [<0000000000811ee2>] blk_execute_rq_nowait+0x72/0x80
> [  566.531660]  [<0000000000811f66>] blk_execute_rq+0x76/0xb8
> [  566.531778]  [<0000000000830d0e>] bsg_ioctl+0x426/0x500
> [  566.531787]  [<0000000000440cb4>] do_vfs_ioctl+0x68c/0x710
> [  566.531794]  [<0000000000440dac>] ksys_ioctl+0x74/0xa0
> [  566.531801]  [<0000000000440e0a>] sys_ioctl+0x32/0x40
> [  566.531808]  [<0000000000bf1dd0>] system_call+0xd8/0x2d0
> [  566.531815] 1 lock held by bsg_api_test/3104:
> [  566.531821]  #0: 00000000cb4b58e8 (rcu_read_lock){....}, at: hctx_lock+0x30/0x118
> 
> And then it dies completely:
> 
> [  566.531854] Unable to handle kernel pointer dereference in virtual kernel address space
> [  566.531861] Failing address: 0000000000000000 TEID: 0000000000000483
> [  566.531867] Fault in home space mode while using kernel ASCE.
> [  566.531885] AS:00000000013ec007 R3:00000000effc8007 S:00000000effce000 P:000000000000013d
> [  566.531927] Oops: 0004 ilc:3 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [  566.531938] Modules linked in: ...
> [  566.532042] CPU: 3 PID: 3104 Comm: bsg_api_test Tainted: G        W         4.19.0-rc6-bb-next+ #1
> [  566.532047] Hardware name: IBM 3906 M03 704 (LPAR)
> [  566.532051] Krnl PSW : 00000000d16c67b2 00000000e4a74b5c (zfcp_fc_exec_bsg_job+0x116/0x2c0 [zfcp])
> [  566.532071]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:3 PM:0 RI:0 EA:3
> [  566.532077] Krnl GPRS: 0000000000001000 00000000bfb84178 0000000000000001 0000000080000004
> [  566.532082]            0000000000001000 00000000a6625108 0000000000000000 0000000000000001
> [  566.532086]            00000000bfb870e8 0000000000000000 00000000b6276930 00000000bb3a6fc8
> [  566.532091]            00000000b6276800 000003ff80306228 000003ff802fc048 00000000a7313830
> [  566.532104] Krnl Code: 000003ff802fc090: a7740004            brc     7,3ff802fc098
> [  566.532104]            000003ff802fc094: a7f4002e            brc     15,3ff802fc0f0
> [  566.532104]           #000003ff802fc098: e310a0300004        lg      %r1,48(%r10)
> [  566.532104]           >000003ff802fc09e: e31090000024        stg     %r1,0(%r9)
> [  566.532104]            000003ff802fc0a4: e310a0400004        lg      %r1,64(%r10)
> [  566.532104]            000003ff802fc0aa: e3a090180024        stg     %r10,24(%r9)
> [  566.532104]            000003ff802fc0b0: e31090080024        stg     %r1,8(%r9)
> [  566.532104]            000003ff802fc0b6: 58108000            l       %r1,0(%r8)
> [  566.532143] Call Trace:
> [  566.532149] ([<00000000be459dd8>] 0xbe459dd8)
> [  566.532160]  [<000003ff802bba00>] fc_bsg_dispatch+0x1d0/0x248 [scsi_transport_fc]
> [  566.532164]  [<00000000008319a4>] bsg_queue_rq+0xe4/0x118
> [  566.532169]  [<000000000081ab56>] blk_mq_dispatch_rq_list+0x37e/0x670
> [  566.532174]  [<000000000082050e>] blk_mq_do_dispatch_sched+0x11e/0x130
> [  566.532178]  [<0000000000820dfe>] blk_mq_sched_dispatch_requests+0x156/0x1a0
> [  566.532183]  [<0000000000817564>] __blk_mq_run_hw_queue+0x144/0x160
> [  566.532188]  [<0000000000817614>] __blk_mq_delay_run_hw_queue+0x94/0x218
> [  566.532193]  [<00000000008178b2>] blk_mq_run_hw_queue+0xda/0xf0
> [  566.532197]  [<00000000008211d8>] blk_mq_sched_insert_request+0x1a8/0x1e8
> [  566.532202]  [<0000000000811ee2>] blk_execute_rq_nowait+0x72/0x80
> [  566.532207]  [<0000000000811f66>] blk_execute_rq+0x76/0xb8
> [  566.532211]  [<0000000000830d0e>] bsg_ioctl+0x426/0x500
> [  566.532215]  [<0000000000440cb4>] do_vfs_ioctl+0x68c/0x710
> [  566.532220]  [<0000000000440dac>] ksys_ioctl+0x74/0xa0
> [  566.532224]  [<0000000000440e0a>] sys_ioctl+0x32/0x40
> [  566.532228]  [<0000000000bf1dd0>] system_call+0xd8/0x2d0
> [  566.532231] INFO: lockdep is turned off.
> [  566.532234] Last Breaking-Event-Address:
> [  566.532243]  [<000003ff802fc090>] zfcp_fc_exec_bsg_job+0x108/0x2c0 [zfcp]
> [  566.532247]
> [  566.532250] Kernel panic - not syncing: Fatal exception: panic_on_oops
> 
> This is the state of your branch from an hour ago or so.

The first one is an easy fix, not sure how I missed that. The other
one I have no idea, any chance you could try with this one:

http://git.kernel.dk/cgit/linux-block/commit/?h=mq-conversions&id=142dc9f36e3113b6a76d472978c33c8c2a2b702c

which fixes the first one, and also corrects a wrong end_io call,
but I don't think that's the cause of the above.

If it crashes, can you figure out where in the source that is?
Basically just do

gdb vmlinux
l *zfcp_fc_exec_bsg_job+0x116

assuming that works fine on s390 :-)

-- 
Jens Axboe




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