For instance, we have /sys/kernel/debug/tracing/events/block/block_bio_complete and block_rq_complete which is basically IO completion trace points for ftrace, I believe. Using sudo blktrace -d /dev/sdb1 -o - | blkparse -i - we might see a line like this:
8,33 1 3 0.001086286 0 C RA 1158137880 + 8 [0]
^ IO completion action
The C here is the IO completion event according to the documentation but is this the same as block_bio_complete or is it somehow different. Checking the source code, I can see at https://elixir.bootlin.com/linux/v5.6/source/block/blk-core.c#L1441:
trace_block_rq_complete(req, blk_status_to_errno(error), nr_bytes);
And at https://elixir.bootlin.com/linux/v5.6/source/block/bio.c#L1863:
trace_block_bio_complete(bio->bi_disk->queue, bio, blk_status_to_errno(bio->bi_status));
Which of the two is the C action? Or does blktrace use a separate set of actions - searches tell me ftrace and blktrace use different reporting mechanisms, but I cannot work out how each tracepoint for both mechanisms relate to kernel source code. Is there an easy way to map tracepoints to source code?
