On Thu, Jul 12, 2018 at 11:30:32AM -0700, Andy Lutomirski wrote:
>
> > On Jul 12, 2018, at 11:03 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> >> On Thu, Jul 12, 2018 at 06:20:24PM +0100, Al Viro wrote:
> >>> On Thu, Jul 12, 2018 at 07:15:05PM +0200, Greg KH wrote:
> >>>> On Tue, Jul 10, 2018 at 11:44:09PM +0100, David Howells wrote:
> >>>> Provide an fsopen() system call that starts the process of preparing to
> >>>> create a superblock that will then be mountable, using an fd as a context
> >>>> handle. fsopen() is given the name of the filesystem that will be used:
> >>>>
> >>>> int mfd = fsopen(const char *fsname, unsigned int flags);
> >>>>
> >>>> where flags can be 0 or FSOPEN_CLOEXEC.
> >>>>
> >>>> For example:
> >>>>
> >>>> sfd = fsopen("ext4", FSOPEN_CLOEXEC);
> >>>> write(sfd, "s /dev/sdb1"); // note I'm ignoring write's length arg
> >>>> write(sfd, "o noatime");
> >>>> write(sfd, "o acl");
> >>>> write(sfd, "o user_attr");
> >>>> write(sfd, "o iversion");
> >>>> write(sfd, "o ");
> >>>> write(sfd, "r /my/container"); // root inside the fs
> >>>> write(sfd, "x create"); // create the superblock
> >>>
> >>> Ugh, creating configfs again in a syscall form? I know people love
> >>> file descriptors, but can't you do this with a configfs entry instead if
> >>> you really want to do this type of thing from userspace in this type of
> >>> "style"?
> >>>
> >>> Why reinvent the wheel again?
> >>
> >> The damn thing REALLY, REALLY depends upon the fs type. How would
> >> you map it on configfs?
> >
> > /sys/kernel/config/fs/ext4/ would work, right? Each fs "type" would be
> > listed there.
> >
> > Anyway, the whole "write a bunch of options and then do a 'create'" is
> > exactly the way configfs works. Why not use that?
> >
> >
>
> How do you mount configfs in the first place? And how do you use this
> in a mount namespace without a private configfs instance or where you
> don’t want configfs mounted?--
Ok, fair enough, I missed the part where this is going to replace
mount(2). Although you could just use mount(2) to mount configfs on a
mount point in the initramfs image and then go from there at boot time :)
/me runs away...
