Re: [dm-devel] dm: free io_barrier after blk_cleanup_queue call

[Tahsin Erdogan]

On Mon, Oct 10, 2016 at 6:25 AM, Mike Snitzer  wrote:
> I have to believe this was born out of code inspection rather than
> actual need (due to crash, etc)?

This got originated from several crashes I have seen with 4.3 kernel.
The crashes
were caused by null dereferencing of io_barrier->per_cpu_ref.

The issue may no longer be relevant after commit c91852ff0815
("dm: optimize dm_request_fn()") because conditions for accessing
io_barrier may not longer exist. But fix should be considered for
forked stable trees.

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[dm-devel] [PATCH] dm: fix parameter to blk_delay_queue()

[Tahsin Erdogan]

Second parameter to blk_delay_queue() must be in msec units not jiffies.

Signed-off-by: Tahsin Erdogan <tah...@google.com>
---
 drivers/md/dm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1b2f96205361..17c63265a205 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2175,7 +2175,7 @@ static void dm_request_fn(struct request_queue *q)
 md_in_flight(md) && rq->bio && rq->bio->bi_vcnt == 1 &&
 md->last_rq_pos == pos && md->last_rq_rw == 
rq_data_dir(rq)) ||
(ti->type->busy && ti->type->busy(ti))) {
-   blk_delay_queue(q, HZ / 100);
+   blk_delay_queue(q, 10);
return;
}
 
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2.8.0.rc3.226.g39d4020

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Re: [dm-devel] dm: fix parameter to blk_delay_queue()

[Tahsin Erdogan]

> This needs to be rebased against linux-next (or linux-dm.git's
> 'for-next') because the code in question has been moved out to dm-rq.c
>
> But I'll gladly take care of it.

Thanks Mike!

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