| title: | Re PATCH 4 5 dm implement REQ FLUSH FUA s |
|
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... thats 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 wont be plugged and
restarted later leading to queue hang. Ill 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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