Re: bio linked list corruption.

[Chris Mason]

On Wed, Oct 26, 2016 at 05:20:01PM -0600, Jens Axboe wrote:
> On 10/26/2016 05:08 PM, Linus Torvalds wrote:
> > On Wed, Oct 26, 2016 at 4:03 PM, Jens Axboe <axboe@xxxxxx> wrote:
> > > Actually, I think I see what might trigger it. You are on nvme, iirc,
> > > and that has a deep queue.
> >
> > Yes. I have long since moved on from slow disks, so all my systems are
> > not just flash, but m.2 nvme ssd's.
> >
> > So at least that could explain why Dave sees it at bootup but I don't.
>
> Yep, you'd never sleep during normal boot. The original patch had a
> problem, though... This one should be better. Too many 'data's, we'll
> still need to assign ctx/hctx, we should just use the current ones, not
> the original ones.
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index ddc2eed64771..e56fec187ba6 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1217,9 +1224,9 @@ static struct request *blk_mq_map_request(struct 
> request_queue *q,
> 	blk_mq_set_alloc_data(&alloc_data, q, 0, ctx, hctx);
> 	rq = __blk_mq_alloc_request(&alloc_data, op, op_flags);
>
> -	hctx->queued++;
> -	data->hctx = hctx;
> -	data->ctx = ctx;
> +	data->hctx = alloc_data.hctx;
> +	data->ctx = alloc_data.ctx;
> +	data->hctx->queued++;
> 	return rq;
> }

This made it through an entire dbench 2048 run on btrfs.  My script has 
it running in a loop, but this is farther than I've gotten before.  
Looking great so far.

-chris