On Thu, Apr 16, 2020 at 01:47:50PM +0800, Ming Lei wrote: > On Thu, Apr 16, 2020 at 05:25:24AM +0000, Luis Chamberlain wrote: > > On Thu, Apr 16, 2020 at 10:10:36AM +0800, Ming Lei wrote: > > > In theory, multiple partitions can be traced concurrently, but looks > > > it never works, so it won't cause trouble for multiple partition trace. > > > > > > One userspace visible change is that blktrace debugfs dir name is switched > > > to disk name from partition name in case of partition trace, will it > > > break some utilities? > > > > How is this possible, its not clear to me, we go from: > > > > - q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent), > > - blk_debugfs_root); > > > > To this: > > > > + q->debugfs_dir = debugfs_create_dir(kobject_name(q->kobj.parent), > > + blk_debugfs_root); > > > > > > Maybe I am overlooking something. > > Your patch removes the blktrace debugfs dir: > > do_blk_trace_setup() > > - dir = debugfs_lookup(buts->name, blk_debugfs_root); > - if (!dir) > - bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root); > - > > Then create blktrace attributes under the dir of q->debugfs_dir. > > However, buts->name could be one partition device name, but I can see how buts->name is set to bdevname() which expands to disk_name(bdev->bd_disk, bdev->bd_part->partno, buf). > q->debugfs_dir has to be disk name. I can't see this, can you point me to where it is clear the request_queue kobject's parent is sure to be the disk name? If it is different, the issue I don't think should be debugfs, but the bigger issue would be that blktrace on two different partitions would clash. Also, the *old* lookup intent on partitions always would fail on mq and we'd end up creating a directory. I think we'd need to create a directory per partition, even when we don't use blktrace. That makes this more complex than I'd hope for. Luis
