[PATCH and question]: dm-table should check for valid queue

[PATCH and question]: dm-table should check for valid queue

[Stefan Bader]

[-- Attachment #1: Type: text/plain, Size: 631 bytes --]

Hi,

in some cases it is possible that bdev_get_queue() returns NULL. And
there are some places where device-mapper just uses the returned pointer
to call queue functions. The attached patch adds this to
dm_table_unplug_all() and dm_table_flush_all(). I treated a device
without a queue as sort of successfully flushed. Is this what would be
expected?
Same problem with dm_table_any_congested() which I didn't change, yet.
This function should probably also check before using
q->backing_dev_info. But what effect should a missing queue have? Same
as device is congested or not or let the call fail somehow?

Regards,
Stefan Bader

[-- Attachment #2: dm-table-checkreqq.diff --]
[-- Type: text/plain, Size: 692 bytes --]

diff -Nurp linux-RHEL4/drivers/md/dm-table.c linux-RHEL4-BTM/drivers/md/dm-table.c
--- linux-RHEL4/drivers/md/dm-table.c	2006-08-07 13:15:30.000000000 +0200
+++ linux-RHEL4-BTM/drivers/md/dm-table.c	2005-10-06 15:34:15.000000000 +0200
@@ -917,7 +917,7 @@ void dm_table_unplug_all(struct dm_table
 		struct dm_dev *dd = list_entry(d, struct dm_dev, list);
 		request_queue_t *q = bdev_get_queue(dd->bdev);
 
-		if (q && q->unplug_fn)
+		if (q->unplug_fn)
 			q->unplug_fn(q);
 	}
 }
@@ -932,9 +932,6 @@ int dm_table_flush_all(struct dm_table *
 		request_queue_t *q = bdev_get_queue(dd->bdev);
 		int err;
 
-		if (!q)
-			continue;
-
 		if (!q->issue_flush_fn)
 			err = -EOPNOTSUPP;
 		else

[-- Attachment #3: Type: text/plain, Size: 0 bytes --]

Re: [PATCH and question]: dm-table should check for valid queue

[Alasdair G Kergon]

On Thu, Aug 10, 2006 at 01:29:08PM +0200, Stefan Bader wrote:
> But what effect should a missing queue have? Same
> as device is congested or not or let the call fail somehow?
 
I'm curious - under what circumstances is this missing:
Is it intentional, or is it perhaps a race that needs fixing?

Alasdair
-- 
agk@redhat.com