On Mon, Dec 10 2018 at 5:45pm -0500,
Jens Axboe <axboe@xxxxxxxxx> wrote:
> After switching to percpu inflight counters, the inflight check
> is totally buggy. It's perfectly valid for some counters to be
> non-zero while having a total inflight IO count of 0, that's how
> these kinds of counters work (inc on one CPU, dec on another).
> Fix the md_in_flight() check to sum all counters before returning
> a false positive, potentially.
>
> While at it, remove the inflight read for IO completion. We don't
> need it, just wake anyone that's waiting for the IO count to drop
> to zero. The caller needs to re-check that value anyway when woken,
> which it does.
>
> Fixes: 6f75723190d8 ("dm: remove the pending IO accounting")
> Reported-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
I'm seeing that device-mapper-test-suite's "resize_io" test doesn't
pass. Glad this resolves the xfstest issue but I think more work is
needed, so I'll build any additional changes on this fix.
Thanks.
Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx>
>
> ---
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 70568f8b6c53..79ad4b3d215c 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -650,14 +650,14 @@ static bool md_in_flight(struct mapped_device *md)
> {
> int cpu;
> struct hd_struct *part = &dm_disk(md)->part0;
> + long sum = 0;
>
> for_each_possible_cpu(cpu) {
> - if (part_stat_local_read_cpu(part, in_flight[0], cpu) ||
> - part_stat_local_read_cpu(part, in_flight[1], cpu))
> - return true;
> + sum += part_stat_local_read_cpu(part, in_flight[0], cpu);
> + sum += part_stat_local_read_cpu(part, in_flight[1], cpu);
> }
>
> - return false;
> + return sum != 0;
> }
Heh, amazing any tests passed.. sorry for this
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