linux-kernel - Re: linux-3.14 nfsd regression

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Date:	Thu, 03 Apr 2014 16:48:11 -0400
From:	Mark Lord <mlord@...ox.com>
To:	"J. Bruce Fields" <bfields@...hat.com>
CC:	Albert Fluegel <af@....de>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: linux-3.14 nfsd regression

On 14-04-03 03:30 PM, J. Bruce Fields wrote:
> On Thu, Apr 03, 2014 at 01:51:06PM -0400, Mark Lord wrote:
>> On 14-04-03 01:16 PM, J. Bruce Fields wrote:
>>> On Thu, Apr 03, 2014 at 12:33:55PM -0400, Mark Lord wrote:
>>>> This commit from linux-3.14 breaks our NFS-root clients here:
>>>>
>>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6e14b46b91fee8a049b0940333ce13a820beaaa5
>>>>
>>>>
>>>> - *p++ = htonl((u32) stat->mode);
>>>> + *p++ = htonl((u32) (stat->mode & S_IALLUGO));
>>>>
>>>>
>>>> Reverting the one-liner above (on the server) fixes it for us,
>>>> as does reverting back to linux-3.13.8 on the server.
>>>>
>>>> The NFS-root clients are on PowerPC (big-endian) architecture,
>>>> running linux-3.12.16. The NFS server is on an Intel PC running linux-3.14.
>>>>
>>>> ACL is completely disabled on server and client,
>>>> and we're using NFSv2/v3.  No support for v4.
>>>>
>>>> I instrumented the function to see what other bits were being cleared
>>>> by the (stat->mode & S_IALLUGO) masking.  The results are attached.
>>>
>>> Hm, it sounds like a bug in the client if it's depending on those high
>>> bits.
>>
>> But only for mounting / starting up from the nfsroot, it seems.
>> I wonder if there's an unusual code path for that in there?
>> The regular stuff looks mostly fine:
>>
>>         p = xdr_decode_ftype3(p, &fmode);
>>         fattr->mode = (be32_to_cpup(p++) & ~S_IFMT) | fmode;
> 
> Hm, but that's in nfs3xdr.c; in nfs2xdr.c we have just
> 
> 	fattr->mode = be32_to_cpup(p+);
> 
> and NFSv2 is the default for nfsroot.  Do you have some reason to
> believe you're not using NFSv2?

Oh, the client here was using NFS2, absolutely.
I just don't know my way around the code very well yet.  :)

But that mask in nfs3xdr.c (client) doesn't match what the server side is using.
-- 
Mark Lord
Real-Time Remedies Inc.
mlord@...ox.com
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