Phew, well, since we did't hear back about removing scsi-generic blktrace functionality I put work into addressing to keep it. That took a lot of code inspection and also testing. Since libvirt is limited to what devices you can test I resorted to testing all supported device types with iscsi tcp and tgt.
I decided to simplfiy the partition work further by just using a symbolic link. In the end that makes the blktrace code even cleaner than anything we had before. scsi-generic stuff still required quite a bit of work to figure out what to do. Since scsi devices probe asynchronously and scsi-generic is nothing but a class_interface whose sg_add_device() runs *prior* to the scsi device probe, we currently address the symlink on the sg ioctl. I however think this reveals a shortcoming of the class interface, now that we have async probe and its used widely. I think we need a probe_complete() call or something like that. If that seems reasonable I can work on that, that would allow us to move the debugfs_dir symlink / settings from sg's ioctl to a new proper call. I'd prefer to address that later though, as an evolution. Its my first time touching scsi stuff, so I'd highly appreciate a good review of what I propose for scsi-generic. It gets a bit more complicated with some drivers using the bsg queue. FWIW, if bsg is enabled we *reshare* the request_queue from the scsi_device, unless you're a scsi transport, in which case it creates its own. You can find this on my git tree: https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20200508-block-fixes Luis Chamberlain (5): block: revert back to synchronous request_queue removal block: move main block debugfs initialization to its own file blktrace: fix debugfs use after free blktrace: break out of blktrace setup on concurrent calls loop: be paranoid on exit and prevent new additions / removals block/Makefile | 1 + block/blk-core.c | 32 ++++-- block/blk-debugfs.c | 202 +++++++++++++++++++++++++++++++++++ block/blk-mq-debugfs.c | 5 - block/blk-sysfs.c | 46 ++++---- block/blk.h | 23 ++++ block/bsg.c | 2 + block/genhd.c | 73 ++++++++++++- block/partitions/core.c | 9 ++ drivers/block/loop.c | 4 + drivers/scsi/ch.c | 1 + drivers/scsi/sg.c | 75 +++++++++++++ drivers/scsi/st.c | 2 + include/linux/blkdev.h | 6 +- include/linux/blktrace_api.h | 1 - include/linux/genhd.h | 69 ++++++++++++ kernel/trace/blktrace.c | 33 ++++-- 17 files changed, 539 insertions(+), 45 deletions(-) create mode 100644 block/blk-debugfs.c -- 2.25.1
