On Tue, Oct 31, 2023 at 01:14:42PM +0100, Christian Brauner wrote: > What happens in the kernel right now I've mentiond in the mount api > conversion patch for btrfs I sent out in June at [1] because I tweaked > that behavior. Say I mount both subvolumes: > > mount /dev/sda -o subvol=subvol1 /vol1 # sb1@vfsmount1 > mount /dev/sda -o subvol=subvol2 /vol2 # sb1@vfsmount2 > > It creates a superblock for /dev/sda. It then creates two vfsmounts: one > for subvol1 and one for subvol2. So you end up with two subvolumes on > the same superblock. > > So if you mount a subvolume today then you already get separate > vfsmounts. To put it another way. If you start 10,000 containers each > using a separate btrfs subvolume then you get 10,000 vfsmounts. But only if you mount them explicitly, which you don't have to. > Or is it that you want a separate superblock per subvolume? Does "you" refer to me here? No, I don't. > Because only > if you allocate a new superblock you'll get clean device number > handling, no? Or am I misunderstanding this? If you allocate a super block you get it for free. If you don't you have to manually allocate it report it in ->getattr.
