Messages in this thread | | | Subject | Re: [PATCH 5/5] btrfs: ioctl: Call btrfs_vol_uevent on subvolume deletion | From | Marcos Paulo de Souza <> | Date | Fri, 25 Oct 2019 12:44:20 -0300 |
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On Fri, 2019-10-25 at 13:00 +0100, Graham Cobb wrote: > On 24/10/2019 03:36, Marcos Paulo de Souza wrote: > > From: Marcos Paulo de Souza <mpdesouza@suse.com> > > > > Since the function btrfs_ioctl_snap_destroy is used for deleting > both > > subvolumes and snapshots it was needed call btrfs_is_snapshot, > > which checks a giver btrfs_root and returns true if it's a > snapshot. > > The current code is interested in subvolumes only. > > To me, as a user, a snapshot *is* a subvolume. I don't even know what > "is a snapshot" means. Does it mean "was created using the btrfs > subvolume snapshot command"? Does it matter whether the snapshot has > been modified? Whether the originally snapshot subvolume still > exists? > Or what? > > I note that the man page for "btrfs subvolume" says "A snapshot is a > subvolume like any other, with given initial content.". And I > certainly > have some subvolumes which are being used as normal parts of the > filesystem, which were originally created as snapshots (for various > reasons, including reverting changes and going back to an earlier > snapshot, or an easy way to make sure that large common files are > actually sharing blocks).
Agreed.
> > I would expect this event would be generated for any subvolume > deletion. > If it is useful to distinguish subvolumes originally created as > snapshots in some way then export another flag (named to make it > clear > what it really indicates, such as BTRFS_VOL_FROM_SNAPSHOT). I don't > know > your particular purpose, but my guess is that a more useful flag > might > actually be BTRFS_VOL_FROM_READONLY_SNAPSHOT.
As soon as these patches got merged I will send new ones to take care of snapshoting. Same things: when a snapsoht is created or removed, send a uevent.
I liked this idea to separate both snapshots and volumes at first to make things simpler, and get reviews faster. Also, I think it's good to separate subvolumes and snapshot events, makes easier for one to filter such events.
Marcos
> > Graham
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