Commit 6625d091 authored May 04, 2016 by Chuck Lever Committed by J. Bruce Fields May 13, 2016

svcrdma: Do not add XDR padding to xdr_buf page vector



An xdr_buf has a head, a vector of pages, and a tail. Each
RPC request is presented to the NFS server contained in an
xdr_buf.

The RDMA transport would like to supply the NFS server with only
the NFS WRITE payload bytes in the page vector. In some common
cases, that would allow the NFS server to swap those pages right
into the target file's page cache.

Have the transport's RDMA Read logic put XDR pad bytes in the tail
iovec, and not in the pages that hold the data payload.

The NFSv3 WRITE XDR decoder is finicky about the lengths involved,
so make sure it is looking in the correct places when computing
the total length of the incoming NFS WRITE request.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent 696190ea

fs/nfsd/nfs3xdr.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -379,7 +379,7 @@ nfs3svc_decode_writeargs(struct svc_rqst rqstp, __be32 p,
		*/
		hdr = (void*)p - rqstp->rq_arg.head[0].iov_base;
		dlen = rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len
		- hdr;
		+ rqstp->rq_arg.tail[0].iov_len - hdr;
		/*
		* Round the length of the data which was specified up to
		* the next multiple of XDR units and then compare that

net/sunrpc/xprtrdma/svc_rdma_recvfrom.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -488,7 +488,7 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt,
		if (page_offset & 3) {
		u32 pad = 4 - (page_offset & 3);

		head->arg.page_len += pad;
		head->arg.tail[0].iov_len += pad;
		head->arg.len += pad;
		head->arg.buflen += pad;
		page_offset += pad;

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