Re: [PATCH 4/5] blk-mq-debugfs: Show busy requests

Bart Van Assche
2017-05-26T21:22:37Z

On Fri, 2017-05-26 at 15:20 -0600, Jens Axboe wrote:
> On 05/26/2017 03:17 PM, Bart Van Assche wrote:
> > On Fri, 2017-05-26 at 07:26 -0600, Jens Axboe wrote:
> > > On 05/25/2017 05:38 PM, Bart Van Assche wrote:
> > > > Requests that got stuck in a block driver are neither on
> > > > blk_mq_ctx.rq_list nor on any hw dispatch queue. Make these
> > > > visible in debugfs through the "busy" attribute.
> > > >=20
> > > > Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> > > > Cc: Christoph Hellwig <hch@lst.de>
> > > > Cc: Hannes Reinecke <hare@suse.com>
> > > > Cc: Omar Sandoval <osandov@fb.com>
> > > > Cc: Ming Lei <ming.lei@redhat.com>
> > > > ---
> > > > block/blk-mq-debugfs.c | 25 +++++++++++++++++++++++++
> > > > 1 file changed, 25 insertions(+)
> > > >=20
> > > > diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
> > > > index 8b06a12c1461..70a2b955afee 100644
> > > > --- a/block/blk-mq-debugfs.c
> > > > +++ b/block/blk-mq-debugfs.c
> > > > @@ -370,6 +370,30 @@ static const struct seq_operations hctx_dispat=
ch_seq_ops =3D {
> > > > .show =3D blk_mq_debugfs_rq_show,
> > > > };
> > > > =20
> > > > +struct show_busy_ctx {
> > > > + struct seq_file *m;
> > > > + struct blk_mq_hw_ctx *hctx;
> > > > +};
> > > > +
> > > > +static void hctx_show_busy(struct request *rq, void *data, bool re=
served)
> > > > +{
> > > > + const struct show_busy_ctx *ctx =3D data;
> > >=20
> > > Let's not call that variable 'ctx', in blk-mq that's pretty much
> > > reserved for the sw queues.
> >=20
> > Hello Jens,
> >=20
> > How about renaming show_busy_ctx into show_busy_params and ctx into par=
ams?
>=20
> I think that would be an improvement. Also, this:
>=20
> blk_mq_debugfs_rq_show(ctx->m, &rq->queuelist);
>=20
> doesn't look safe at all, as you are passing in a node instead of a
> head. I think you just want to use __blk_mq_debugfs_rq_show() here.

Hello Jens,

That change will make the compiler perform type checking. I agree that's
an improvement. I will make that change.

Bart.=