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

[Joe Eykholt]

On 7/31/10 6:49 PM, FUJITA Tomonori wrote:
> 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.

I tried it with my module (not with ibmvstgt) and it seems to work better.
Here's the patch I used (cut-and-paste from stg so for illustration only).
Feel free to do something different.  If setting rq->bio = NULL is OK,
it might be better.  I haven't researched this enough to know what's best.

Author: Joe Eykholt <jeykholt at cisco.com>
Date:   Tue Aug 3 12:33:07 2010 -0700

     stgt: fix warning from __blk_put_request()

     Every ftgt I/O ending was getting a WARNING and stack dump
     from block/blk-core:1080 __blk_put_request() because a request
     still had a bio associated with it.

     Call blk_end_request_all() after unmapping the user pages.

     Signed-off-by: Joe Eykholt <jeykholt at cisco.com>

diff --git a/drivers/scsi/scsi_tgt_lib.c b/drivers/scsi/scsi_tgt_lib.c
index 1030327..a454ed0 100644
--- a/drivers/scsi/scsi_tgt_lib.c
+++ b/drivers/scsi/scsi_tgt_lib.c
@@ -151,6 +151,7 @@ void scsi_host_put_command(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
  	kmem_cache_free(scsi_tgt_cmd_cache, tcmd);

  	spin_lock_irqsave(q->queue_lock, flags);
+	__blk_end_request_all(rq, 0);
  	__blk_put_request(q, rq);
  	spin_unlock_irqrestore(q->queue_lock, flags);

--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo at vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html