linux-kernel - Re: asm-generic/unistd.h and glibc use of NR

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Message-Id: <201009291355.06512.arnd@arndb.de>
Date:	Wed, 29 Sep 2010 13:55:06 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Chris Metcalf <cmetcalf@...era.com>, linasvepstas@...il.com,
	GLIBC Devel <libc-alpha@...rceware.org>,
	linux-kernel@...r.kernel.org, libc-ports@...rceware.org
Subject: Re: asm-generic/unistd.h and glibc use of NR_ipc

On Wednesday 29 September 2010, Christoph Hellwig wrote:
> On Tue, Sep 28, 2010 at 09:05:13AM -0400, Chris Metcalf wrote:
> > Another point where I'd appreciate guidance from libc-alpha is the sysctl()
> > and ustat() APIs.  The corresponding system calls are missing from
> > <asm-generic/unistd.h>, since they are deprecated and their functionality
> > is better provided by other means (/proc/sys, fstat).  So I've simply had
> > them return -1 with errno == ENOSYS.  Is there any reason to think they
> > merit more substantial work?  One could imagine baking in some horrible
> > mapping of "integer names" into path components for a sysctl()
> > implementation and reading /proc/sys to provide results, or walking all of
> > the mount points looking for a matching device number to pass a name to
> > fstat(), but I'm not sure it's worth the bloat to the library.
> 
> fstat does not replace ustat.  ustat is a statf-subsystem by dev_t and
> is not replaced by anything.  xfsprogs for example uses it to check if
> a given dev_t is currently mounted.  Please add it to the generic code.
> 

I didn't put it into the generic list because the man page claims

 "ustat() is deprecated and has only been provided for compatibility.
  All new programs should use statfs(2) instead."

I suppose that means we should change the man page as well, right?

	Arnd
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