linux-kernel - Re: [GIT PULL] Please pull NFS client changes

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Date:	Fri, 11 Sep 2015 13:06:07 -0400
From:	Trond Myklebust <trond.myklebust@...marydata.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Drokin <green@...uxhacker.ru>,
	Doug Ledford <dledford@...hat.com>
Subject: Re: [GIT PULL] Please pull NFS client changes

On Fri, Sep 11, 2015 at 12:27 PM, Christoph Hellwig <hch@...radead.org> wrote:
> On Mon, Sep 07, 2015 at 11:01:36PM -0700, Christoph Hellwig wrote:
>> On Tue, Sep 08, 2015 at 11:59:00AM +1000, Stephen Rothwell wrote:
>> > This contains about 12 commits new since Sept 1 and the last 6 are only
>> > appearing in linux-next today (though I did not do Friday and Monday's
>> > linux-next).  Not judging, just noting.
>>
>> And one of tese recent commits causes a regression for block layouts
>> in xfstests generic/075.  Still need to check which one.
>
> "NFSv4.1/pNFS: Don't request a minimal read layout beyond the end of file"
>
> is the culprit, posted to the list for the first time and committed on
> Aug 31.

That looks like it is tickling a server protocol bug.

The minimum length is just that; a minimum. If the server wants the
layout to be block aligned, then it is supposed to adjust the returned
offset + length values so that they cover the range described by the
offset+minimum length (see table 13 on
https://tools.ietf.org/html/rfc5661#page-540).
The server is only supposed to fail the LAYOUTGET request if it is
completely unable to meet those requirements. Furthermore, it is
supposed to return either NFS4ERR_BADLAYOUT or NFS4ERR_LAYOUTTRYLATER
(depending on what the value of the minimum layout was); as far as I
can see, the current code is returning NFS4ERR_LAYOUTUNAVAILABLE.

Cheers,
  Trond
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