On Sun, Jun 3, 2018 at 2:55 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> On Sat, Jun 02, 2018 at 06:49:58PM +0100, Al Viro wrote:
>
>> > > Hell, might even add AT_UMOUNT for "open root and detach, to be dissolved on
>> > > close", incompatible with AT_CLONE.
>> >
>> > Cute. Guess you could do:
>> >
>> > fd = open_mount(..., OPEN_TREE_DETACH);
>> > mount_setattr(fd, "",
>> > MOUNT_SETATTR_EMPTY_PATH,
>> > MOUNT_SETATTR_NOSUID, NULL);
>> > move_mount(fd, "", ...);
>
> Hadn't added that yet, but as for the rest of open_tree() - see
> vfs.git#mount-open_tree. open() and its flags are not touched at all.
> Other changes compared to the previous:
> * may_mount() is required for OPEN_TREE_CLONE
> * sys_ni.c cruft is dropped - those make no sense until and unless
> those syscalls become conditional.
>
> Appears to work, combined with move_mount() it yields eqiuvalents of
> mount --{move,bind,rbind}. Combined with mount_setattr(2) (when that
> gets added) we'll get mount -o remount,bind,nodev et.al.
fsopen = create fsfd
fsmount = fsfd -> mountfd & set attr on mountfd & attach mountfd
fspick = path -> fsfd
move_mount = attach mountfd or move existing
fsinfo = info from path
open_tree = new mountfd from path or clone
mount_setattr = set attr on mountfd
Notice that fsmount() encompasses mount_setattr() + move_mount()
functionality. Split those out and leave fsmount() to actually do
the "fsfd ->mountfd" translation?
fsinfo() name suggests it's in the same class as
fsopen/fsmount/fspick, operating on fsfd object, but's it's not and I
think that's slightly confusing.
Rename move_mount() -> mount_move()?
Also does it make sense to make the cloning behavior of open_tree()
optional? Without cloning it's just a plain open(O_PATH). That way
it could be renamed mount_clone().
Thanks,
Miklos
