> 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?--
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