On Mon, Oct 23, 2023 at 05:35:25PM +0200, Christian Brauner wrote: > I just realized that if we're able to deprecate LOOP_CHANGE_FD we remove > one of the most problematic/weird cases for partitions and filesystems. > change fd event on the first partition: > > sudo ./loop_change_fd /dev/loop0p1 img2 > > we call disk_force_media_change() but that only works on disk->part0 > which means that we don't even cleanly shutdown the filesystem on the > partition we're trying to mess around with. Yes, disk_force_media_change has that general problem back from the early Linux days (it had a different name back then, though). I think it is because traditionally removable media in Linux never had partitions, e.g. the CDROM drivers typically only allocated a single minor number so they could not be scanned. But that has changed because the interfaces got used for different use cases, and we also had dynamic majors for a long time that now allow partitions. And there are real use cases even for traditional removable media, e.g. MacOS CDROMs traditionally did have partitions. > For now, we should give up any pretense that disk_force_media_change() > does anything useful for loop change fd and simply remove it completely. > It's either useless, or it breaks the original semantics of loop change > fd although I don't think anyone's ever used it the way I described > above. Maybe we can just drop the CHANGE_FD ioctl and see if anyone screams?
