On Mon, Nov 06, 2023 at 06:48:11PM +1030, Qu Wenruo wrote: > > st_dev has only been very historically about treating something as > > a device. For userspae the most important part is that it designates > > a separate domain for inode numbers. And that's something that's simply > > broken in btrfs. > > In fact, I'm not sure if the "treating something as a device" thing is even > correct long before btrfs. It never really has been. There's just two APIs that ever did this, ustat and the old quotactl. Both have been deprecated a long time ago and never hid wide use. > For example, for an EXT4 fs with external log device. Thankfully it's still > more or less obvious we would use the device number of the main fs, not the > log device, but we already had such examples. More relevant (as the log device never has persistent data) is the XFS realtime device.
