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

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Message-Id: <67C35F5E-7CB0-4CE9-998F-D9871E0DAF81@linuxhacker.ru>
Date:	Fri, 8 Jul 2016 23:41:41 -0400
From:	Oleg Drokin <green@...uxhacker.ru>
To:	Al Viro <viro@...IV.linux.org.uk>,
	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	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 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?