On 06/25/12 21:35, James Bottomley wrote:
> On Mon, 2012-06-25 at 14:21 -0700, Tejun Heo wrote:
>> Hey, James.
>>
>> On Mon, Jun 25, 2012 at 10:14:49PM +0100, James Bottomley wrote:
>>>> @@ -1490,11 +1489,7 @@ static void scsi_request_fn(struct request_queue *q)
>>>> struct scsi_cmnd *cmd;
>>>> struct request *req;
>>>>
>>>> - if (!sdev) {
>>>> - while ((req = blk_peek_request(q)) != NULL)
>>>> - scsi_kill_request(req, q);
>>>> - return;
>>>> - }
>>>
>>> That means that this hunk of code has to stay, but needs to be gated on
>>> blk_queue_dead(q); there's still a race where this can occur.
>>
>> Wouldn't the scsi_device_online() check down below be enough? Block
>> layer drain is gonna loop until all requests are done, so the looping
>> is handled from block layer.
>
> It might be ... in theory the teardown is supposed to happen in
> SDEV_CANCEL and be done by SDEV_DEL. However, I'm not sure that's
> entirely true now. blk_queue_dead() is safer since we know we just
> killed the queue. Another reason for doing it like this is that the
> kill on queue dead isn't noisy ... the one on !online is ... and logs
> were getting stuffed with messages about killing requests to dead
> queues.
That log filling was fixed by commit 7457181. Without patch 2/4 of this
series a single message is printed when a request is killed because the
queue is dead ("killing request"). With patch 2/4 two messages are
printed ("rejecting I/O to offline device" + "killing request"). I can
suppress the first message by inserting an additional if statement if you
want, e.g. as follows (compile-tested only):
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index dcef9b8..e307314 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1506,7 +1506,8 @@ static void scsi_request_fn(struct request_queue *q)
break;
if (unlikely(!scsi_device_online(sdev))) {
- sdev_printk(KERN_ERR, sdev,
+ if (!blk_queue_dead(q))
+ sdev_printk(KERN_ERR, sdev,
"rejecting I/O to offline device\n");
scsi_kill_request(req, q);
continue;
Bart.
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