netdev - Re: Boot failure when using NFS on OMAP based evms

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Date:	Thu, 7 Apr 2016 10:39:42 -0400
From:	Willem de Bruijn <willemb@...gle.com>
To:	"Franklin S Cooper Jr." <fcooper@...com>
Cc:	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Sam Kumar <samanthakumar@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>, tony@...mide.com,
	mugunthanvnm@...com, Network Development <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, Patrick McHardy <kaber@...sh.net>,
	nsekhar@...com, linux-omap@...r.kernel.org
Subject: Re: Boot failure when using NFS on OMAP based evms

On Thu, Apr 7, 2016 at 10:36 AM, Franklin S Cooper Jr. <fcooper@...com> wrote:
>
>
> On 04/06/2016 09:22 PM, Willem de Bruijn wrote:
>> On Wed, Apr 6, 2016 at 7:12 PM, Franklin S Cooper Jr. <fcooper@...com> wrote:
>>> Hi All,
>>>
>>> Currently linux-next is failing to boot via NFS on my AM335x GP evm,
>>> AM437x GP evm and Beagle X15. I bisected the problem down to the commit
>>> "udp: remove headers from UDP packets before queueing".
>>>
>>> I had to revert the following three commits to get things working again:
>>>
>>> e6afc8ace6dd5cef5e812f26c72579da8806f5ac
>>> udp: remove headers from UDP packets before queueing
>>>
>>> 627d2d6b550094d88f9e518e15967e7bf906ebbf
>>> udp: enable MSG_PEEK at non-zero offset
>>>
>>> b9bb53f3836f4eb2bdeb3447be11042bd29c2408
>>> sock: convert sk_peek_offset functions to WRITE_ONCE
>>>
>>
>> Thanks for the report, and apologies for breaking your configuration.
>> I had missed that sunrpc can dequeue skbs from a udp receive
>> queue and makes assumptions about the layout of those packets. rxrpc
>> does the same. From what I can tell so far, those are the only two
>> protocols that do this. I have verified that the following fixes rxrpc for me
>>
>> --- a/net/rxrpc/ar-input.c
>> +++ b/net/rxrpc/ar-input.c
>> @@ -612,9 +612,9 @@ int rxrpc_extract_header(struct rxrpc_skb_priv
>> *sp, struct sk_buff *skb)
>>         struct rxrpc_wire_header whdr;
>>
>>         /* dig out the RxRPC connection details */
>> -       if (skb_copy_bits(skb, sizeof(struct udphdr), &whdr, sizeof(whdr)) < 0)
>> +       if (skb_copy_bits(skb, 0, &whdr, sizeof(whdr)) < 0)
>>                 return -EBADMSG;
>> -       if (!pskb_pull(skb, sizeof(struct udphdr) + sizeof(whdr)))
>> +       if (!pskb_pull(skb, sizeof(whdr)))
>>                 BUG();
>>
>> I have not yet been able to reproduce the sunrpc/nfs issue, but I
>> suspect that the following might fix it. I will try to create an NFS
>> setup.
>>
>> diff --git a/net/sunrpc/socklib.c b/net/sunrpc/socklib.c
>> index 2df87f7..8ab40ba 100644
>> --- a/net/sunrpc/socklib.c
>> +++ b/net/sunrpc/socklib.c
>> @@ -155,7 +155,7 @@ int csum_partial_copy_to_xdr(struct xdr_buf *xdr,
>> struct sk_buff *skb)
>>         struct xdr_skb_reader   desc;
>>
>>         desc.skb = skb;
>> -       desc.offset = sizeof(struct udphdr);
>> +       desc.offset = 0;
>>         desc.count = skb->len - desc.offset;
>>
>>         if (skb_csum_unnecessary(skb))
>> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
>> index 1413cdc..71d6072 100644
>> --- a/net/sunrpc/svcsock.c
>> +++ b/net/sunrpc/svcsock.c
>> @@ -617,7 +617,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
>>         svsk->sk_sk->sk_stamp = skb->tstamp;
>>         set_bit(XPT_DATA, &svsk->sk_xprt.xpt_flags); /* there may be
>> more data... */
>>
>> -       len  = skb->len - sizeof(struct udphdr);
>> +       len  = skb->len;
>>         rqstp->rq_arg.len = len;
>>
>>         rqstp->rq_prot = IPPROTO_UDP;
>> @@ -641,8 +641,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
>>                 skb_free_datagram_locked(svsk->sk_sk, skb);
>>         } else {
>>                 /* we can use it in-place */
>> -               rqstp->rq_arg.head[0].iov_base = skb->data +
>> -                       sizeof(struct udphdr);
>> +               rqstp->rq_arg.head[0].iov_base = skb->data;
>>                 rqstp->rq_arg.head[0].iov_len = len;
>>                 if (skb_checksum_complete(skb))
>>                         goto out_free;
>> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
>> index 65e7595..c1fc7b2 100644
>> --- a/net/sunrpc/xprtsock.c
>> +++ b/net/sunrpc/xprtsock.c
>> @@ -995,15 +995,14 @@ static void xs_udp_data_read_skb(struct rpc_xprt *xprt,
>>         u32 _xid;
>>         __be32 *xp;
>>
>> -       repsize = skb->len - sizeof(struct udphdr);
>> +       repsize = skb->len;
>>         if (repsize < 4) {
>>                 dprintk("RPC:       impossible RPC reply size %d!\n", repsize);
>>                 return;
>>         }
>>
>>
>>
>>         /* Copy the XID from the skb... */
>> -       xp = skb_header_pointer(skb, sizeof(struct udphdr),
>> -                               sizeof(_xid), &_xid);
>> +       xp = skb_header_pointer(skb, 0, sizeof(_xid), &_xid);
>>         if (xp == NULL)
>>                 return;
>>
>
>
> Thank you for your quick response. I verified with all of the above
> suggested changes that NFS works again on my 3 evms.

Thanks a lot for testing, Franklin. I will send out the two patches.