On 05/26/2017 08:38 AM, Hannes Reinecke wrote: > On 05/26/2017 01:38 AM, 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 <[email protected]> >> Cc: Christoph Hellwig <[email protected]> >> Cc: Hannes Reinecke <[email protected]> >> Cc: Omar Sandoval <[email protected]> >> Cc: Ming Lei <[email protected]> >> --- >> block/blk-mq-debugfs.c | 25 +++++++++++++++++++++++++ >> 1 file changed, 25 insertions(+) >> >> 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_dispatch_seq_ops = { >> .show = blk_mq_debugfs_rq_show, >> }; >> >> +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; >> + >> + if (blk_mq_map_queue(rq->q, rq->mq_ctx->cpu) == ctx->hctx && >> + test_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) >> + blk_mq_debugfs_rq_show(ctx->m, &rq->queuelist); >> +} >> + >> +static int hctx_busy_show(void *data, struct seq_file *m) >> +{ >> + struct blk_mq_hw_ctx *hctx = data; >> + 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_ctx_map_show(void *data, struct seq_file *m) >> { >> struct blk_mq_hw_ctx *hctx = data; >> @@ -705,6 +729,7 @@ static const struct blk_mq_debugfs_attr >> blk_mq_debugfs_hctx_attrs[] = { >> {"state", 0400, hctx_state_show}, >> {"flags", 0400, hctx_flags_show}, >> {"dispatch", 0400, .seq_ops = &hctx_dispatch_seq_ops}, >> + {"busy", 0400, hctx_busy_show}, >> {"ctx_map", 0400, hctx_ctx_map_show}, >> {"tags", 0400, hctx_tags_show}, >> {"tags_bitmap", 0400, hctx_tags_bitmap_show}, >> > Hmm. I wonder if this is going to work as intended; 'busy' might be > changing rapidly, so the busy_iter might be giving us unintended results. > Have you checked?
That's true for _any_ of the debugfs exports for probing into internals that hold/store requests. All of them are just a snapshot in time, there's no intent (or posibility) for these to be stable in any way. -- Jens Axboe
