blk-mq-debugfs: Show busy requests

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>
Reviewed-by: Eduardo Valentin <eduval@amazon.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>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 8b06a12c1461..90c454bbaf92 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -370,6 +370,36 @@ static const struct seq_operations hctx_dispatch_seq_ops = {
         .show   = blk_mq_debugfs_rq_show,
 };
 
+struct show_busy_params {
+        struct seq_file         *m;
+        struct blk_mq_hw_ctx    *hctx;
+};
+
+/*
+ * Note: the state of a request may change while this function is in progress,
+ * e.g. due to a concurrent blk_mq_finish_request() call.
+ */
+static void hctx_show_busy_rq(struct request *rq, void *data, bool reserved)
+{
+        const struct show_busy_params *params = data;
+
+        if (blk_mq_map_queue(rq->q, rq->mq_ctx->cpu) == params->hctx &&
+            test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
+                __blk_mq_debugfs_rq_show(params->m,
+                                         list_entry_rq(&rq->queuelist));
+}
+
+static int hctx_busy_show(void *data, struct seq_file *m)
+{
+        struct blk_mq_hw_ctx *hctx = data;
+        struct show_busy_params params = { .m = m, .hctx = hctx };
+
+        blk_mq_tagset_busy_iter(hctx->queue->tag_set, hctx_show_busy_rq,
+                                &params);
+
+        return 0;
+}
+
 static int hctx_ctx_map_show(void *data, struct seq_file *m)
 {
         struct blk_mq_hw_ctx *hctx = data;
@@ -705,6 +735,7 @@ 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},