On Fri, Jan 26, 2018 at 4:08 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
>
>> On Jan 26, 2018, at 12:13 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
>>
>> On Fri, Jan 26, 2018 at 2:29 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>>>
>>>
>>>> On Jan 26, 2018, at 11:05 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
>>>>
>>>> On Fri, Jan 26, 2018 at 1:23 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>>> On Jan 26, 2018, at 9:24 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
>>>>>>
>>>>>> Hi Bruce/Chuck,
>>>>>>
>>>>>> There is a problem with nfsd doing a WRITE of size 4093,4094,4095. To
>>>>>> reproduce, mount with RDMA and do a simple dd "dd if=/dev/zero
>>>>>> of=/mnt/testfile bs=4093 count=1". What happens is that nfsd fails to
>>>>>> parse GETATTR after the WRITE in the compound. It fails the operation
>>>>>> with ERR_OP_ILLEGAL.
>>>>>>
>>>>>> The problem happens for the values where XDR round up ends up rounding
>>>>>> up to the page size. I don't know if my fix is the appropriate way to
>>>>>> fix this but with it I don't get the error:
>>>>>>
>>>>>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>>>>>> index 2c61c6b..a8489c3 100644
>>>>>> --- a/fs/nfsd/nfs4xdr.c
>>>>>> +++ b/fs/nfsd/nfs4xdr.c
>>>>>> @@ -1289,11 +1289,12 @@ static __be32 nfsd4_decode_opaque(struct nfsd4_compounda
>>>>>>
>>>>>> len = XDR_QUADLEN(write->wr_buflen) << 2;
>>>>>> if (len >= avail) {
>>>>>> - int pages;
>>>>>> + int pages = 0;
>>>>>>
>>>>>> len -= avail;
>>>>>>
>>>>>> - pages = len >> PAGE_SHIFT;
>>>>>> + if (write->wr_buflen >= PAGE_SIZE)
>>>>>> + pages = len >> PAGE_SHIFT;
>>>>>> argp->pagelist += pages;
>>>>>> argp->pagelen -= pages * PAGE_SIZE;
>>>>>> len -= pages * PAGE_SIZE;
>>>>>>
>>>>>> So the problem is the using "len" instead of "write->wr_buflen" leads
>>>>>> for the values 4093,4094,4095 that are rounded up to 4096, it makes
>>>>>> pages=1 and the argp->pagelen ends up being a negative value leading
>>>>>> to problems of parsing the GETATTR.
>>>>>
>>>>> Would this also be a problem near any page boundary, say, a
>>>>> write length of 8191 bytes?
>>>>>
>>>>> Instead of using the rounded up "len", why not try this:
>>>>>
>>>>> - pages = len >> PAGE_SHIFT;
>>>>> + pages = write->wr_buflen >> PAGE_SHIFT;
>>>>
>>>> You are right. It needs to be that. Otherwise 8191 fails the same way.
>>>>
>>>>> And be sure to test with TCP as well.
>>>>
>>>> Sigh. It breaks normal (non-RDMA) mounts. I'll figure out why.
>>>
>>> OK.
>>>
>>> Remember that a Read chunk's length does not have to be
>>> rounded up. Maybe the transport needs to round up the
>>> length of the unmarshaled data content on behalf of the
>>> NFSv4 write decoder.
>>>
>>
>> The problem of simply taking write->wr_buflen was that len before that
>> could have been adjusted by avail value in then non-RDAM mounts.
>>
>> Again, I'm not sure if this is the right fix. But this one works for
>> both non-RDMA and RDMA mounts.
>>
>> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
>> index 2c61c6b..3178997 100644
>> --- a/fs/nfsd/nfs4xdr.c
>> +++ b/fs/nfsd/nfs4xdr.c
>> @@ -1293,7 +1293,10 @@ static __be32 nfsd4_decode_opaque(struct
>> nfsd4_compoundargs *argp, struct xdr_ne
>>
>> len -= avail;
>>
>> - pages = len >> PAGE_SHIFT;
>> + if (!avail)
>> + pages = write->wr_buflen >> PAGE_SHIFT;
>> + else
>> + pages = len >> PAGE_SHIFT;
>> argp->pagelist += pages;
>> argp->pagelen -= pages * PAGE_SIZE;
>> len -= pages * PAGE_SIZE;
>
> This code has been around since 2012. Has it always been
> broken for RDMA? I suspect the root problem is in the
> transport, not here in the decoder. Can you bisect to
> find out where the problem started to occur?
To see if I could go back to 2012, I first want to see if I could go
back to before mlx5 driver was added which was in 3.11-rc1. But I'm
having issues trying to boot into a kernel based on 3.10 or 3.9. I'm
trying to verify if my CX-5 card would even work with mlx4 driver
which I'm having doubts it would. These old kernels fail to boot in
XFS saying that it's a wrong version. Some googling makes me think
that since my XFS partition was created with a newer kernel it's not
compatible with an older kernel...
>>>>>> If this looks OK, I can send a patch.
>>>>>> --
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>>>>>
>>>>> --
>>>>> Chuck Lever
>>>>>
>>>>>
>>>>>
>>>>> --
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>>>
>>> --
>>> Chuck Lever
>>>
>>>
>>>
>> --
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>
> --
> Chuck Lever
>
>
>
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