Re: [PATCH v1 10/12] xprtrdma: Fix large NFS SYMLINK calls

[Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Jul 14, 2015, at 12:01 PM, Anna Schumaker <schumaker.anna-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Hey Chuck,
> 
> On 07/09/2015 04:43 PM, Chuck Lever wrote:
>> Repair how rpcrdma_marshal_req() chooses which RDMA message type
>> to use for large non-WRITE operations so that it picks RDMA_NOMSG
>> in the correct situations, and sets up the marshaling logic to
>> SEND only the RPC/RDMA header.
>> 
>> Large NFSv2 SYMLINK requests now use RDMA_NOMSG calls. The Linux NFS
>> server XDR decoder for NFSv2 SYMLINK does not handle having the
>> pathname argument arrive in a separate buffer. The decoder could be
>> fixed, but this is simpler and RDMA_NOMSG can be used in a variety
>> of other situations.
>> 
>> Ensure that the Linux client continues to use "RDMA_MSG + read
>> list" when sending large NFSv3 SYMLINK requests, which is more
>> efficient than using RDMA_NOMSG.
>> 
>> Large NFSv4 CREATE(NF4LNK) requests are changed to use "RDMA_MSG +
>> read list" just like NFSv3 (see Section 5 of RFC 5667). Before,
>> these did not work at all.
>> 
>> Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
>> ---
>> fs/nfs/nfs3xdr.c               |    1 +
>> fs/nfs/nfs4xdr.c               |    1 +
>> net/sunrpc/xprtrdma/rpc_rdma.c |   21 ++++++++++++---------
>> 3 files changed, 14 insertions(+), 9 deletions(-)
> 
> It might be better to split this into separate patches for nfs and sunrpc, since Trond might want to accept the nfs changes separately.

Originally I had the fs/nfs/*xdr.c changes split into separate patches.
But I’ve convinced myself that it is better to bundle the NFS changes
with the rpc_rdma.c changes here.

If the fs/nfs/*xdr.c changes come before the rpc_rdma.c changes, then
the XDRBUF_WRITE flag is being set in the NFS XDR encoders, but never
used anywhere. Which is safe, but somewhat nonsensical.

If the fs/nfs/*xdr.c changes come after the rpc_rdma.c changes, then
the client will send NFSv3 SYMLINK and NFSv4 CREATE(NF4LNK) differently
for a moment when just the rpc_rdma.c change is applied.

Together in a single commit, these are a single indivisible change that
stands up well to bisect, and is easy for distributions to cherry-pick.
It doesn’t make sense to apply the NFS and RPC/RDMA changes separately.

So, it’s up to you and Trond. I will change it if he prefers it broken
out. I think the most benign way to split them is to merge the
fs/nfs/*xdr.c changes first, but let’s hear from Trond.


> Anna
> 
>> 
>> diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
>> index 9b04c2e..267126d 100644
>> --- a/fs/nfs/nfs3xdr.c
>> +++ b/fs/nfs/nfs3xdr.c
>> @@ -1103,6 +1103,7 @@ static void nfs3_xdr_enc_symlink3args(struct rpc_rqst *req,
>> {
>> 	encode_diropargs3(xdr, args->fromfh, args->fromname, args->fromlen);
>> 	encode_symlinkdata3(xdr, args);
>> +	xdr->buf->flags |= XDRBUF_WRITE;
>> }
>> 
>> /*
>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>> index 558cd65d..03a20ec 100644
>> --- a/fs/nfs/nfs4xdr.c
>> +++ b/fs/nfs/nfs4xdr.c
>> @@ -1155,6 +1155,7 @@ static void encode_create(struct xdr_stream *xdr, const struct nfs4_create_arg *
>> 		p = reserve_space(xdr, 4);
>> 		*p = cpu_to_be32(create->u.symlink.len);
>> 		xdr_write_pages(xdr, create->u.symlink.pages, 0, create->u.symlink.len);
>> +		xdr->buf->flags |= XDRBUF_WRITE;
>> 		break;
>> 
>> 	case NF4BLK: case NF4CHR:
>> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
>> index 2e721f2..64fc4b4 100644
>> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
>> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
>> @@ -484,21 +484,24 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
>> 	 *
>> 	 * o If the total request is under the inline threshold, all ops
>> 	 *   are sent as inline.
>> -	 * o Large non-write ops are sent with the entire message as a
>> -	 *   single read chunk (protocol 0-position special case).
>> 	 * o Large write ops transmit data as read chunk(s), header as
>> 	 *   inline.
>> +	 * o Large non-write ops are sent with the entire message as a
>> +	 *   single read chunk (protocol 0-position special case).
>> 	 *
>> -	 * Note: the NFS code sending down multiple argument segments
>> -	 * implies the op is a write.
>> -	 * TBD check NFSv4 setacl
>> +	 * This assumes that the upper layer does not present a request
>> +	 * that both has a data payload, and whose non-data arguments
>> +	 * by themselves are larger than the inline threshold.
>> 	 */
>> -	if (rpcrdma_args_inline(rqst))
>> +	if (rpcrdma_args_inline(rqst)) {
>> 		rtype = rpcrdma_noch;
>> -	else if (rqst->rq_snd_buf.page_len == 0)
>> -		rtype = rpcrdma_areadch;
>> -	else
>> +	} else if (rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
>> 		rtype = rpcrdma_readch;
>> +	} else {
>> +		headerp->rm_type = htonl(RDMA_NOMSG);
>> +		rtype = rpcrdma_areadch;
>> +		rpclen = 0;
>> +	}
>> 
>> 	/* The following simplification is not true forever */
>> 	if (rtype != rpcrdma_noch && wtype == rpcrdma_replych)
>> 
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> 

--
Chuck Lever



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