On Wed, 28 Jul 2021, Neal Gompa wrote: > On Wed, Jul 28, 2021 at 3:02 AM NeilBrown <neilb@xxxxxxx> wrote: > > > > On Wed, 28 Jul 2021, Wang Yugui wrote: > > > Hi, > > > > > > This patchset works well in 5.14-rc3. > > > > Thanks for testing. > > > > > > > > 1, fixed dummy inode(255, BTRFS_FIRST_FREE_OBJECTID - 1 ) is changed to > > > dynamic dummy inode(18446744073709551358, or 18446744073709551359, ...) > > > > The BTRFS_FIRST_FREE_OBJECTID-1 was a just a hack, I never wanted it to > > be permanent. > > The new number is ULONG_MAX - subvol_id (where subvol_id starts at 257 I > > think). > > This is a bit less of a hack. It is an easily available number that is > > fairly unique. > > > > > > > > 2, btrfs subvol mount info is shown in /proc/mounts, even if nfsd/nfs is > > > not used. > > > /dev/sdc btrfs 94G 3.5M 93G 1% /mnt/test > > > /dev/sdc btrfs 94G 3.5M 93G 1% /mnt/test/sub1 > > > /dev/sdc btrfs 94G 3.5M 93G 1% /mnt/test/sub2 > > > > > > This is a visiual feature change for btrfs user. > > > > Hopefully it is an improvement. But it is certainly a change that needs > > to be carefully considered. > > I think this is behavior people generally expect, but I wonder what > the consequences of this would be with huge numbers of subvolumes. If > there are hundreds or thousands of them (which is quite possible on > SUSE systems, for example, with its auto-snapshotting regime), this > would be a mess, wouldn't it? Would there be hundreds or thousands of subvols concurrently being accessed? The auto-mounted subvols only appear in the mount table while that are being accessed, and for about 15 minutes after the last access. I suspect that most subvols are "backup" snapshots which are not being accessed and so would not appear. > > Or can we add a way to mark these things to not show up there or is > there some kind of behavioral change we can make to snapper or other > tools to make them not show up here? Certainly it might make sense to flag these in some way so that tools can choose the ignore them or handle them specially, just as nfsd needs to handle them specially. I was considering a "local" mount flag. NeilBrown > > > > -- > 真実はいつも一つ！/ Always, there's only one truth! > >
