[RFC] Removing a subvolume by an ordinary user

["kreijack@libero.it" <kreijack@libero.it>]

Hi all,

currently BTRFS doesn't allow an ordinary user to remove a subvolume (o=
r=20
snapshot). I think that the reasons is simple: a subvolume may contain=20
files/directories owned by other user.
Allowing an ordinary user to remove a subvolume means allowing an ordin=
ary=20
user to remove filess/directories owned by other user. And this is not =
good.

Moreover BTRFS removes  a subvolume asynchronously, so it is not possib=
le to=20
return an error like =E2=80=9Chey you are trying to remove a not your f=
ile  ! Don=E2=80=99t do=20
it !=E2=80=9D.

My idea is to add another ioctl that permits to remove a subvolume only=
 when=20
it is empty and its host directory is writable by the user=E2=80=A6 lik=
e a directory.=20
An option is to allow to remove an empty subvolume  with the unlink(2) =
syscall:=20
no more tool is needed !=20
This will solve a lot of problem:
-	Consistently with the current unlink(2) behavior
-	The kernel has not to do complicate check
-	There no is necessity to add another interface to wait the releasing =
of the=20
space (see other thread reserving an IOCTL number; other details ).
The disadvantage is that it should be slower than the currently=20
implementation.
Of course I don=E2=80=99t want to remove the existing interface. I want=
 only to add=20
another one.

Comments ? Thoughts ?
Regards
G.Baroncelli=20

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