Hi David,
On Wed, Feb 19, 2020 at 3:36 PM David Howells <dhowells@xxxxxxxxxx> wrote:
> Add system calls to create and remove mountpoints(). These are modelled
> after mkdir and rmdir inside the VFS. Currently they use the same security
> hooks which probably needs fixing.
>
> The calls look like:
>
> long create_mountpoint(int dfd, const char *path,
> const char *fstype, const char *source,
> const char *params);
> long remove_mountpoint(int dfd, const char *path);
>
> Creation takes an fstype, source and params which the filesystem that owns
> the mountpoint gets to filter/interpret. It is free to reject any
> combination of fstype, source and params it cannot store. source and
> params are both optional.
>
> Removal could probably be left to rmdir(), but this gives the option of
> applying tighter security checks and also allows me to prevent rmdir from
> removing them by accident.
>
> The AFS filesystem is then altered to use these system calls to create and
> remove persistent mountpoints in an AFS volume. create_automount() is
> something that AFS needs, but cannot be implemented with, say, symlink().
> These substitute for the lack of pioctl() on Linux, supplying the
> functionality of VIOC_AFS_CREATE_MT_PT and VIOC_AFS_DELETE_MT_PT.
>
> Also make them usable with tmpfs for testing. I'm not sure if this is
> useful in practice, but I've made tmpfs store the three parameters and just
> pass them to mount when triggered. Note that it doesn't look up the target
> filesystem until triggered so as not to load lots of modules until
> necessary.
>
> I suspect they're of little of use to NFS, CIFS and autofs, but probably
> Coda and maybe Btrfs can make use of them.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Thanks for your patch!
The above nicely explains what the patch does.
However, unless I'm missing something, this fails to explain the "why"
(except for the vague "[...] is something that AFS needs ...".
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
