linux-kernel - Re: [PATCH] nfsd: Make creates return EEXIST correctly instead of EPERM

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Date:	Wed, 13 Jul 2016 15:00:29 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Oleg Drokin <green@...uxhacker.ru>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Jeff Layton <jlayton@...chiereds.net>,
	linux-nfs@...r.kernel.org,
	Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nfsd: Make creates return EEXIST correctly instead of
 EPERM

On Fri, Jul 08, 2016 at 11:41:41PM -0400, Oleg Drokin wrote:
> 
> On Jul 8, 2016, at 11:10 PM, Al Viro wrote:
> 
> > On Fri, Jul 08, 2016 at 05:47:22PM -0400, Oleg Drokin wrote:
> > 
> >> I wonder if people just accept that "NFS is just weird" and code in workarounds,
> >> where as with Lustre we promise (almost) full POSIX compliance, and also came much later
> >> so people are just seeing that "this does not work" and complain more loudly?
> > 
> > To quote POSIX: "If more than one error occurs in processing a function call,
> > any one of the possible errors may be returned, as the order of detection is
> > undefined." (from System Interfaces: General Information: 2.3 Error Numbers)
> > 
> > And regarding mkdir(2) it has
> > [EACCES]
> >    Search permission is denied on a component of the path prefix, or write
> > permission is denied on the parent directory of the directory to be created.
> > [EEXIST]
> >    The named file exists.
> > among the error conditions.  In situations when both apply, the implementation
> > is bloody well allowed to return either.  It might be nicer to return EEXIST
> > in such cases, for consistency sake (if another thread does stat() on the
> > pathname in question just as you are about to call mkdir(2), you will get
> > EEXIST without ever reaching permission(9), let alone ->mkdir() method), but
> > please do not bring POSIX compliance as an argument.  It's a QoI argument and
> > nothing beyond that.
> 
> Ok, I see.
> Thanks.
> 
> Bruce, do you want the patch resubmitted with a rewritten commit message,
> or do you think it's best to just drop it them?

Other things being equal I still agree with you that there'd be
advantages to being more consistent, so a changelog update would be
fine.

--b.