On Tue, Oct 07, 2008 at 10:18:40PM +0100, Alasdair G Kergon wrote:
> Meanwhile I will not be applying that patch, though I may take a patch
> to provide clean diagnostics should a situation like this occur again.
I'm thinking of something like this:
From: Alasdair G Kergon <agk@xxxxxxxxxx>
Detect and report buggy drivers that destroy their request_queue.
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Cc: Stefan Raspl <raspl@xxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-table.c | 24 ++++++++++++++++++++++--
1 files changed, 22 insertions(+), 2 deletions(-)
Index: linux-2.6.27-rc8/drivers/md/dm-table.c
===================================================================
--- linux-2.6.27-rc8.orig/drivers/md/dm-table.c 2008-10-09 14:53:35.000000000 +0100
+++ linux-2.6.27-rc8/drivers/md/dm-table.c 2008-10-09 14:56:26.000000000 +0100
@@ -478,6 +478,13 @@ void dm_set_device_limits(struct dm_targ
{
struct request_queue *q = bdev_get_queue(bdev);
struct io_restrictions *rs = &ti->limits;
+ char b[BDEVNAME_SIZE];
+
+ if (unlikely(!q)) {
+ DMWARN("%s: Cannot set limits for nonexistent device %s",
+ dm_device_name(ti->table->md), bdevname(bdev, b));
+ return;
+ }
/*
* Combine the device limits low.
@@ -943,7 +950,14 @@ int dm_table_any_congested(struct dm_tab
list_for_each_entry(dd, devices, list) {
struct request_queue *q = bdev_get_queue(dd->bdev);
- r |= bdi_congested(&q->backing_dev_info, bdi_bits);
+ char b[BDEVNAME_SIZE];
+
+ if (likely(q))
+ r |= bdi_congested(&q->backing_dev_info, bdi_bits);
+ else
+ DMWARN_LIMIT("%s: any_congested: nonexistent device %s",
+ dm_device_name(t->md),
+ bdevname(dd->bdev, b));
}
return r;
@@ -956,8 +970,14 @@ void dm_table_unplug_all(struct dm_table
list_for_each_entry(dd, devices, list) {
struct request_queue *q = bdev_get_queue(dd->bdev);
+ char b[BDEVNAME_SIZE];
- blk_unplug(q);
+ if (likely(q))
+ blk_unplug(q);
+ else
+ DMWARN_LIMIT("%s: Cannot unplug nonexistent device %s",
+ dm_device_name(t->md),
+ bdevname(dd->bdev, b));
}
}
--
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