On Tue, Jun 09, 2020 at 05:29:22PM +0000, Luis Chamberlain wrote: > Is scsi-generic is the only unwanted ugly child blktrace has to deal > with? For some reason I thought drivers/md/md.c was one but it seems > like it is not. Do we have an easy way to search for these? I think > this would just affect how we express the comment only.
grep for blk_trace_setup. For all blk devices that setup comes in through the block device ioctl path, and that relies on having a struct block_device and queue. sg on the other hand calls blk_trace_setup directly with a NULL bdev argument. > > */ > > - dir = q->sg_debugfs_dir; > > + dir = debugfs_create_dir(buts->name, blk_debugfs_root); > > + bt->dir = dir; > > The other chicken and egg problem to consider at least in the comments > is that the debugfs directory for these types of devices *have* an > exposed path, but the data structure is rather opaque to the device and > even blktrace. Fortunately given the recent set of changes around the > q->blk_trace and clarifications around its use we have made it clear now > that so long as hold the q->blk_trace_mutex *and* check q->blk_trace we > *should* not race against two separate creations of debugfs directories, > so I think this is safe, so long as these indpendent drivers don't end > up re-using the same path for some other things later in the future, and > since we have control over what goes under debugfsroot block / I think > we should be good. > > But I think that the concern for race on names may still be worth > explaining a bit here. Feel free to add more comments, but please try to keep them short and crisp. At the some point long comments really distract from what is going on.
