Re: Linux Virtual SCSI HBAs and Virtual disks

[aboo <aboo@aboo.org>]

Thanks Doug Gilber for looking in to this one. I will fix this. This is really useful input. At the moment, the kernel driver can not deal with sense codes. If a SCSI command fails, it returns non 0 return code to kernel SCSI driver. But it does not return any sense codes (It just makes all zero making the SCSI driver think that there is no sense information). I will impliment the sense codes inside the driver so that the kernel part will be stable even if the user space does not support the commands.

I just wanted to pitch this idea infront of everyone. I will make further modification to impliment sense codes.

Also, I am facing another challenge which I wanted to ask. If the kernel or user space opens  a scsi device, there is no healthy way of identifying if a scsi device is open or not. The struct scsi_device does not have a field. I can see a openers field in the scsi_disk structure inside sd.c. I can see it incrimenting in sd_open(). What is the best to way to identify if a scsi_device id open by kernel (mount or volumes manager) or use application (fsck or dd)? When a destroy a scsi_host, it kills all the scsi_devices associated with it irrespective of those devices are open or not. Any thoughts?

I looked at the other scsi drivers like buslogic, qlogic, etc. But they open only one scsi_host per module (Created during module load and destroyed during module unload). Since the module usage goes up when someone opens the scsi_device under, it wont let them unload the module and hence can not destory the scsi_host. But i am creating the scsi host dunamically and need to check if any one opened the scsi_device underneath before destroying the host. Any thoughts?

Aboo

On Wed, 17 Jan 2007 17:20:08 -0500, Douglas Gilbert <dougg@torque.net> wrote:
> Aboo Valappil wrote:
>> Hi All,
>>
>> Thanks everyone to have a look at this.
>>
>> I think i modified to have the latest kernel support. Unfortunately I
>> could not test it with 2.6.20 kernel due to some issues in my laptop and
>> 2.6.20 kernel. But it should work with 2.6.20 with this modification.
>>
>> The modified version is available through
>> http://vscsihba.aboo.org/vscsihbav202.tgz.
>>
>> 1. I fixed the kmem_cache issue for sure.
>> 2. I think i got around with INIT_WORK ... Made the following
>> modifications ...
> 
> Perhaps you could get some of my scsi tools (e.g.
> sdparm and sg3_utils) and make sure that vscsihba
> can handle everything they can throw at it.
> If the user space doesn't support a SCSI command then
> your driver should fail gracefully (i.e. CHECK CONDITION,
> etc).
> 
> Here is a worrying example: sdparm sends an INQUIRY
> and a couple of MODE SENSE(10) commands to a device.
> /dev/sda was created by your script:
> $ ./start_target.sh id=3 -files zz_lun0
> 
> $ sdparm /dev/sda
>     /dev/sda: VirtualH  VHD               0
> <long wait>
> $
> 
> 
> However dmesg showed this:
> 
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> vscsihba:3: In Reset Device
> sd 0:0:0:0: SCSI error: return code = 0x00000002
> end_request: I/O error, dev sda, sector 10240
> Buffer I/O error on device sda, logical block 10240
> BUG: at kernel/sched.c:3388 sub_preempt_count()
>  [<e1bf029c>] scsitap_eh_abort+0x1c/0x90 [vscsihba]
>  [<c024fe22>] scsi_error_handler+0x3e2/0xbe0
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> vscsihba:3: Abortng command serial number : 94
> BUG: scheduling while atomic: scsi_eh_0/0x00000001/4749
>  [<c02d7684>] __sched_text_start+0x484/0x660
>  [<c013183b>] autoremove_wake_function+0x1b/0x50
>  [<c01264a8>] lock_timer_base+0x28/0x70
>  [<c01265f2>] __mod_timer+0x92/0xd0
>  [<c02d826b>] schedule_timeout+0x4b/0xd0
>  [<c01269c0>] process_timeout+0x0/0x10
>  [<c02d7bbc>] wait_for_completion_timeout+0x9c/0x130
>  [<c0119ee0>] default_wake_function+0x0/0x10
>  [<c024f3c9>] scsi_send_eh_cmnd+0x1b9/0x390
>  [<c011df3e>] vprintk+0x1fe/0x3a0
>  [<c024f805>] scsi_delete_timer+0x15/0x60
>  [<c024f624>] scsi_eh_tur+0x34/0xa0
>  [<c024fe69>] scsi_error_handler+0x429/0xbe0
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> vscsihba:3: Abortng command serial number : 95
> vscsihba:3: In Reset Device
> BUG: scheduling while atomic: scsi_eh_0/0x00000001/4749
>  [<c02d7684>] __sched_text_start+0x484/0x660
>  [<c011df3e>] vprintk+0x1fe/0x3a0
>  [<c01264a8>] lock_timer_base+0x28/0x70
>  [<c01265f2>] __mod_timer+0x92/0xd0
>  [<c02d826b>] schedule_timeout+0x4b/0xd0
>  [<c01269c0>] process_timeout+0x0/0x10
>  [<c02d7bbc>] wait_for_completion_timeout+0x9c/0x130
>  [<c0119ee0>] default_wake_function+0x0/0x10
>  [<c024f3c9>] scsi_send_eh_cmnd+0x1b9/0x390
>  [<c024f805>] scsi_delete_timer+0x15/0x60
>  [<c024f624>] scsi_eh_tur+0x34/0xa0
>  [<e1bf00cd>] scsitap_eh_device_reset+0x1d/0x30 [vscsihba]
>  [<c02503a8>] scsi_error_handler+0x968/0xbe0
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> vscsihba:3: Abortng command serial number : 96
> vscsihba:3: In Reset Host
> BUG: scheduling while atomic: scsi_eh_0/0x00000001/4749
>  [<c02d7684>] __sched_text_start+0x484/0x660
>  [<c01264a8>] lock_timer_base+0x28/0x70
>  [<c01265f2>] __mod_timer+0x92/0xd0
>  [<c02d826b>] schedule_timeout+0x4b/0xd0
>  [<c01269c0>] process_timeout+0x0/0x10
>  [<c01273d5>] msleep+0x25/0x30
>  [<c024efb1>] scsi_try_host_reset+0xa1/0xd0
>  [<c0250150>] scsi_error_handler+0x710/0xbe0
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> BUG: scheduling while atomic: scsi_eh_0/0x00000001/4749
>  [<c02d7684>] __sched_text_start+0x484/0x660
>  [<c01264a8>] lock_timer_base+0x28/0x70
>  [<c01265f2>] __mod_timer+0x92/0xd0
>  [<c02d826b>] schedule_timeout+0x4b/0xd0
>  [<c01269c0>] process_timeout+0x0/0x10
>  [<c02d7bbc>] wait_for_completion_timeout+0x9c/0x130
>  [<c0119ee0>] default_wake_function+0x0/0x10
>  [<c024f3c9>] scsi_send_eh_cmnd+0x1b9/0x390
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c01265f2>] __mod_timer+0x92/0xd0
>  [<c02d8272>] schedule_timeout+0x52/0xd0
>  [<c024f624>] scsi_eh_tur+0x34/0xa0
>  [<c02501a0>] scsi_error_handler+0x760/0xbe0
>  [<c02d74f1>] __sched_text_start+0x2f1/0x660
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> vscsihba:3: Abortng command serial number : 97
> sd 0:0:0:0: scsi: Device offlined - not ready after error recovery
> BUG: scheduling while atomic: scsi_eh_0/0x00000001/4749
>  [<c02d7684>] __sched_text_start+0x484/0x660
>  [<c013aa11>] module_put+0x31/0x60
>  [<c024bd6e>] scsi_device_put+0x3e/0x40
>  [<c024be5f>] __scsi_iterate_devices+0x6f/0x90
>  [<c024fa86>] scsi_error_handler+0x46/0xbe0
>  [<c024fa40>] scsi_error_handler+0x0/0xbe0
>  [<c0131679>] kthread+0xa9/0xe0
>  [<c01315d0>] kthread+0x0/0xe0
>  [<c0103d0f>] kernel_thread_helper+0x7/0x18
>  =======================
> 
> 
> Doug Gilbert

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