On Mon, Aug 01 2016 at 2:55P -0400,
Bart Van Assche <bart.vanassche@xxxxxxxxxxx> wrote:
> On 08/01/2016 10:59 AM, Mike Snitzer wrote:
> >This says to me that must_push_back is returning false because
> >dm_noflush_suspending() is false. When this happens -EIO will escape up
> >the IO stack.
> >
> >And this confirms that must_push_back() calling dm_noflush_suspending()
> >is quite suspect given queue_if_no_path was configured: we should
> >_always_ pushback if no paths are available.
> >
> >I'll dig deeper on really understanding _why_ must_push_back() is coded
> >like it is.
>
> Hello Mike,
>
> Earlier I had reported that I observe this behavior with
> CONFIG_DM_MQ_DEFAULT=y after the first simulated cable pull. I have been
> able to reproduce this behavior with CONFIG_DM_MQ_DEFAULT=n but it takes a
> large number of iterations to trigger this behavior. The output that appears
> on my setup in the kernel log with a bunch of printk()'s added in the
> dm-mpath driver for CONFIG_DM_MQ_DEFAULT=n is as follows (mpath 254:0 and
> /dev/mapper/mpathbe refer to the same multipath device):
>
> [ 314.755582] mpath 254:0: queue_if_no_path 0 -> 1
> [ 314.770571] executing DM ioctl DEV_SUSPEND on mpathbe
> [ 314.770622] mpath 254:0: queue_if_no_path 1 -> 0
> [ 314.770657] __multipath_map(): (a) returning -5
> [ 314.770657] map_request(): clone_and_map_rq() returned -5
> [ 314.770658] dm_complete_request: error = -5
Hi Bart,
Please retry both variant (CONFIG_DM_MQ_DEFAULT=y first) with this patch
applied. Interested to see if things look better for you (WARN_ON_ONCEs
added just to see if we hit the corresponding suspend/stopped state
while mapping requests -- if so this speaks to an inherently racey
problem that will need further investigation for a proper fix but
results from this should let us know if we're closer).
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1b2f962..0e0f6e0 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2007,6 +2007,9 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
struct dm_target *ti = tio->ti;
struct request *clone = NULL;
+ if (WARN_ON_ONCE(unlikely(dm_suspended_md(md))))
+ return DM_MAPIO_REQUEUE;
+
if (tio->clone) {
clone = tio->clone;
r = ti->type->map_rq(ti, clone, &tio->info);
@@ -2722,6 +2725,9 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
dm_put_live_table(md, srcu_idx);
}
+ if (WARN_ON_ONCE(unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))))
+ return BLK_MQ_RQ_QUEUE_BUSY;
+
if (ti->type->busy && ti->type->busy(ti))
return BLK_MQ_RQ_QUEUE_BUSY;
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