Hi Jan!

On 2026-05-18T17:05:59+0200, Jan Kara wrote:

quoted

I have more questions about quotactl(2).  In the operations that ignore
the 'id' argument, am I right to assume that QCMD() is unnecessary?  My
assumption is because if there's no user or group ID to be used, it also
doesn't make sense to specify whether we want to affect a user or a
group.

So, for example, Q_QUOTAOFF would have the following synopsis:

	int quotactl(Q_QUOTAOFF, const char *_Nullable special, 0, NULL);

While Q_QUOTAON would have the following one:

	int quotactl(QCMD(Q_QUOTAON, type), const char *_Nullable special,
		     int fmt, caddr_t quota_path);

Is that correct?

No, QCMD() is always required. For example for Q_QUOTAOFF you still need to
tell whether you want to disable user or group quotas. And even if the type
would not matter for some quotactl, QCMD still does a mangling to the
passed arguments that is expected by the kernel (QCMD is ((cmd) <<
SUBCMDSHIFT) | ((type) & SUBCMDMASK)).

Ahh, thanks!  Makes sense.

quoted

Also, I wonder why caddr_t was used at all, instead of void*.  It seems
to unnecessarily require a cast, which could have been avoided with
void*.  In quotactl_fd(), since we need to use syscall(2), which is
variadic, I'll document the correct pointer types, instead of caddr_t*.

For this I don't have a good answer. It was like that for ages... I guess
you can ask glibc guys - the kernel uses void * but glibc uses caddr_t.

Hmmmm.  I'll ask; thanks!


Cheers,
Alex

-- 
<https://www.alejandro-colomar.es>