[stgt] stgt: how to avoid WARNING at block/blk-core.c:1080

[FUJITA Tomonori]

On Fri, 30 Jul 2010 10:32:34 -0700
Joe Eykholt <jeykholt at cisco.com> wrote:

> Hi All,
> 
> I'm working on a target module for scsi_tgt to work with libfc / fcoe
> in Linux 2.6.33.5.  I'm missing some step in handling completion of
> a request.
> 
> After each Inquiry or READ operation, in the transfer_response
> callback I send the data and response and then call the (*done)()
> routine.
> 
> I figure I must be missing something, because I get this WARNING:
> 
> [  271.521650] ------------[ cut here ]------------
> [  271.521658] WARNING: at block/blk-core.c:1080 __blk_put_request+0x4f/0xbe()
> [  271.521660] Hardware name: <snip>
> [  271.521662] Modules linked in: libfc_tgt scsi_tgt nfs lockd nfs_acl auth_rpcgss autofs4 sunrpc ip6t_REJECT 
> nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 dm_multipath uinput fnic libfcoe libfc enic i2c_i801 
> iTCO_wdt serio_raw scsi_transport_fc iTCO_vendor_support pcspkr e1000e shpchp radeon ttm drm_kms_helper drm 
> i2c_algo_bit i2c_core
> [  271.521705] Pid: 2769, comm: scsi_tgtd/2 Tainted: G        W  2.6.33.5-ftgt #9
> [  271.521708] Call Trace:
> [  271.521715]  [<ffffffff811696ae>] ? __blk_put_request+0x4f/0xbe
> [  271.521720]  [<ffffffff81041462>] warn_slowpath_common+0x77/0xa4
> [  271.521724]  [<ffffffff8104149e>] warn_slowpath_null+0xf/0x11
> [  271.521728]  [<ffffffff811696ae>] __blk_put_request+0x4f/0xbe
> [  271.521735]  [<ffffffffa02b14b7>] scsi_host_put_command+0x52/0x80 [scsi_tgt]
> [  271.521740]  [<ffffffffa02b14e5>] ? scsi_tgt_cmd_destroy+0x0/0x3f [scsi_tgt]
> [  271.521745]  [<ffffffffa02b151f>] scsi_tgt_cmd_destroy+0x3a/0x3f [scsi_tgt]
> [  271.521751]  [<ffffffff810513a0>] worker_thread+0x131/0x1bd
> [  271.521756]  [<ffffffff81054bfc>] ? autoremove_wake_function+0x0/0x38
> [  271.521760]  [<ffffffff8105126f>] ? worker_thread+0x0/0x1bd
> [  271.521764]  [<ffffffff810547fe>] kthread+0x7d/0x85
> [  271.521770]  [<ffffffff810099a4>] kernel_thread_helper+0x4/0x10
> [  271.521774]  [<ffffffff81054781>] ? kthread+0x0/0x85
> [  271.521779]  [<ffffffff810099a0>] ? kernel_thread_helper+0x0/0x10
> [  271.521782] ---[ end trace 096013af4d0a82a0 ]---
> 
> It's this code in block/blk-core.c:
> 
> void __blk_put_request(struct request_queue *q, struct request *req)
> {
>          if (unlikely(!q))
>                  return;
>          if (unlikely(--req->ref_count))
>                  return;
> 
>          elv_completed_request(q, req);
> 
>          /* this is a bio leak */
>          WARN_ON(req->bio != NULL);
> 
> 	...
> 
> So, what should I be doing to tell the block layer that the request is done?
> Or, is there something that scsi_tgt should be doing to disassociate the bio
> from the req?

Maybe we should call blk_end_request_all().

But I don't think that bio is leaked in our case. So setting req->bio
to NULL might be fine.

I can't access to my IBM POWER box now but I'll try later.
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