On 08/30/2010 11:28 PM, Mike Snitzer wrote:
> On Mon, Aug 30 2010 at 3:08pm -0400,
> Mike Snitzer <snitzer@xxxxxxxxxx> wrote:
>
>> On Mon, Aug 30 2010 at 11:07am -0400,
>> Tejun Heo <tj@xxxxxxxxxx> wrote:
>>
>>> On 08/30/2010 03:59 PM, Tejun Heo wrote:
>>>> Ah... that's probably from "if (!elv_queue_empty(q))" check below,
>>>> flushes are on a separate queue but I forgot to update
>>>> elv_queue_empty() to check the flush queue. elv_queue_empty() can
>>>> return %true spuriously in which case the queue won't be plugged and
>>>> restarted later leading to queue hang. I'll fix elv_queue_empty().
>>>
>>> I think I was too quick to blame elv_queue_empty(). Can you please
>>> test whether the following patch fixes the hang?
>>
>> It does, thanks!
>
> Hmm, but unfortunately I was too quick to say the patch fixed the hang.
>
> It is much more rare, but I can still get a hang. I just got the
> following running vgcreate against an DM mpath (rq-based) device:
Can you please try this one instead?
Thanks.
---
block/blk-flush.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
Index: block/block/blk-flush.c
===================================================================
--- block.orig/block/blk-flush.c
+++ block/block/blk-flush.c
@@ -56,22 +56,38 @@ static struct request *blk_flush_complet
return next_rq;
}
+static void blk_flush_complete_seq_end_io(struct request_queue *q,
+ unsigned seq, int error)
+{
+ bool was_empty = elv_queue_empty(q);
+ struct request *next_rq;
+
+ next_rq = blk_flush_complete_seq(q, seq, error);
+
+ /*
+ * Moving a request silently to empty queue_head may stall the
+ * queue. Kick the queue in those cases.
+ */
+ if (next_rq && was_empty)
+ __blk_run_queue(q);
+}
+
static void pre_flush_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
- blk_flush_complete_seq(rq->q, QUEUE_FSEQ_PREFLUSH, error);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_PREFLUSH, error);
}
static void flush_data_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
- blk_flush_complete_seq(rq->q, QUEUE_FSEQ_DATA, error);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_DATA, error);
}
static void post_flush_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
- blk_flush_complete_seq(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
+ blk_flush_complete_seq_end_io(rq->q, QUEUE_FSEQ_POSTFLUSH, error);
}
static void init_flush_request(struct request *rq, struct gendisk *disk)
--
tejun
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