Re: [PATCH v1] man/man2/quotactl.2: tfix

Alejandro Colomar <[email protected]> Mon, 18 May 2026 17:12:27 +0200

Newsgroups	org.kernel.vger.linux-man
Message-ID	<agsrnqainyp3vZbX@devuan>

Hi Jan!

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

> > 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>

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