Re: [PATCH 5/6] blk-mq-debugfs: Show busy requests

[Omar Sandoval <osandov@osandov.com>]

On Thu, Apr 27, 2017 at 08:54:36AM -0700, 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.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Cc: Hannes Reinecke <hare@suse.com>
> ---
>  block/blk-mq-debugfs.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
> index 5092d90e37f6..a5e286e04569 100644
> --- a/block/blk-mq-debugfs.c
> +++ b/block/blk-mq-debugfs.c
> @@ -428,6 +428,43 @@ static const struct file_operations hctx_dispatch_fops = {
>  	.release	= seq_release,
>  };
>  
> +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 reserved)
> +{
> +	const struct show_busy_ctx *ctx = data;
> +	struct request_queue *q = rq->q;
> +
> +	if (q->queue_hw_ctx[rq->mq_ctx->index_hw] == ctx->hctx &&

This doesn't look right. ctx->index_hw is the index into hctx->ctxs for
this ctx. I think you mean blk_mq_map_queue(q, rq->mq_ctx->cpu).

> +	    test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
> +		blk_mq_debugfs_rq_show(ctx->m, &rq->queuelist);
> +}
> +
> +static int hctx_busy_show(struct seq_file *m, void *v)
> +{
> +	struct blk_mq_hw_ctx *hctx = m->private;
> +	struct show_busy_ctx ctx = { .m = m, .hctx = hctx };
> +
> +	blk_mq_tagset_busy_iter(hctx->queue->tag_set, hctx_show_busy, &ctx);
> +
> +	return 0;
> +}
> +
> +static int hctx_busy_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, hctx_busy_show, inode->i_private);
> +}
> +
> +static const struct file_operations hctx_busy_fops = {
> +	.open		= hctx_busy_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= single_release,
> +};
> +
>  static int hctx_ctx_map_show(struct seq_file *m, void *v)
>  {
>  	struct blk_mq_hw_ctx *hctx = m->private;
> @@ -885,6 +922,7 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
>  	{"state", 0400, &hctx_state_fops},
>  	{"flags", 0400, &hctx_flags_fops},
>  	{"dispatch", 0400, &hctx_dispatch_fops},
> +	{"busy", 0400, &hctx_busy_fops},
>  	{"ctx_map", 0400, &hctx_ctx_map_fops},
>  	{"tags", 0400, &hctx_tags_fops},
>  	{"tags_bitmap", 0400, &hctx_tags_bitmap_fops},
> -- 
> 2.12.2
>