Re: [PATCH 2/3] Stop accepting SCSI requests before removing a device

[Mike Christie <michaelc@xxxxxxxxxxx>]

On 05/04/2012 03:16 PM, Mike Christie wrote:
> On 05/04/2012 10:06 AM, Bart Van Assche wrote:
>> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
>> index 42c35ff..f8fc240 100644
>> --- a/drivers/scsi/scsi_sysfs.c
>> +++ b/drivers/scsi/scsi_sysfs.c
>> @@ -955,12 +955,20 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
>>  void __scsi_remove_device(struct scsi_device *sdev)
>>  {
>>  	struct device *dev = &sdev->sdev_gendev;
>> +	struct request_queue *q = sdev->request_queue;
>> +
>> +	/*
>> +	 * Stop accepting new requests before tearing down the
>> +	 * device. Note: the actual queue deallocation happens in
>> +	 * scsi_device_dev_release_usercontext().
>> +	 */
>> +	blk_cleanup_queue(q);
>>  
>>  	if (sdev->is_visible) {
>>  		if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
>>  			return;
>>  
>> -		bsg_unregister_queue(sdev->request_queue);
>> +		bsg_unregister_queue(q);
>>  		device_unregister(&sdev->sdev_dev);
>>  		transport_remove_device(dev);
>>  		device_del(dev);
>> @@ -971,8 +979,6 @@ void __scsi_remove_device(struct scsi_device *sdev)
> 
> My fault. The blk_cleanup_queue call should be right before the
> scsi_device_set_state(sdev, SDEV_DEL); call in this function.
> 
> It needs to be after the device_del call, because that triggers the SCSI
> ULD removal which can send IO.
> 

I made the attached patch. It allows the scsi ULD removal IO to execute
ok. I tested with iscsi devices that have write caches.

With your patch I get:

Apr 27 19:09:51 noisyr6 kernel: sd 11:0:0:1: [sdc] Synchronizing SCSI cache
Apr 27 19:09:51 noisyr6 kernel: sd 11:0:0:1: [sdc] Result:
hostbyte=DID_TRANSPORT_FAILFAST driverbyte=DRIVER_OK


With my patch I just get:

May  4 16:29:27 noisyr6 kernel: sd 8:0:0:1: [sdc] Synchronizing SCSI cache

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 42c35ff..11dc3ff 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -955,24 +955,30 @@ int scsi_sysfs_add_sdev(struct scsi_device *sdev)
 void __scsi_remove_device(struct scsi_device *sdev)
 {
 	struct device *dev = &sdev->sdev_gendev;
+	struct request_queue *q = sdev->request_queue;
 
 	if (sdev->is_visible) {
 		if (scsi_device_set_state(sdev, SDEV_CANCEL) != 0)
 			return;
 
-		bsg_unregister_queue(sdev->request_queue);
+		bsg_unregister_queue(q);
 		device_unregister(&sdev->sdev_dev);
 		transport_remove_device(dev);
 		device_del(dev);
 	} else
 		put_device(&sdev->sdev_dev);
+	/*
+	 * Stop accepting new requests before tearing down the
+	 * queue. Note: the actual queue deallocation happens in
+	 * scsi_device_dev_release_usercontext().
+	 */
+	blk_cleanup_queue(q);
+
 	scsi_device_set_state(sdev, SDEV_DEL);
 	if (sdev->host->hostt->slave_destroy)
 		sdev->host->hostt->slave_destroy(sdev);
 	transport_destroy_device(dev);
 
-	/* Freeing the queue signals to block that we're done */
-	blk_cleanup_queue(sdev->request_queue);
 	put_device(dev);
 }