rpc_rdma.c

linux 内核源代码

/*
 * Copyright (c) 2003-2007 Network Appliance, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the BSD-type
 * license below:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *      Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *      Redistributions in binary form must reproduce the above
 *      copyright notice, this list of conditions and the following
 *      disclaimer in the documentation and/or other materials provided
 *      with the distribution.
 *
 *      Neither the name of the Network Appliance, Inc. nor the names of
 *      its contributors may be used to endorse or promote products
 *      derived from this software without specific prior written
 *      permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * rpc_rdma.c
 *
 * This file contains the guts of the RPC RDMA protocol, and
 * does marshaling/unmarshaling, etc. It is also where interfacing
 * to the Linux RPC framework lives.
 */

#include "xprt_rdma.h"

#include <linux/highmem.h>

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

enum rpcrdma_chunktype {
	rpcrdma_noch = 0,
	rpcrdma_readch,
	rpcrdma_areadch,
	rpcrdma_writech,
	rpcrdma_replych
};

#ifdef RPC_DEBUG
static const char transfertypes[][12] = {
	"pure inline",	/* no chunks */
	" read chunk",	/* some argument via rdma read */
	"*read chunk",	/* entire request via rdma read */
	"write chunk",	/* some result via rdma write */
	"reply chunk"	/* entire reply via rdma write */
};
#endif

/*
 * Chunk assembly from upper layer xdr_buf.
 *
 * Prepare the passed-in xdr_buf into representation as RPC/RDMA chunk
 * elements. Segments are then coalesced when registered, if possible
 * within the selected memreg mode.
 *
 * Note, this routine is never called if the connection's memory
 * registration strategy is 0 (bounce buffers).
 */

static int
rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, int pos,
	enum rpcrdma_chunktype type, struct rpcrdma_mr_seg *seg, int nsegs)
{
	int len, n = 0, p;

	if (pos == 0 && xdrbuf->head[0].iov_len) {
		seg[n].mr_page = NULL;
		seg[n].mr_offset = xdrbuf->head[0].iov_base;
		seg[n].mr_len = xdrbuf->head[0].iov_len;
		++n;
	}

	if (xdrbuf->page_len && (xdrbuf->pages[0] != NULL)) {
		if (n == nsegs)
			return 0;
		seg[n].mr_page = xdrbuf->pages[0];
		seg[n].mr_offset = (void *)(unsigned long) xdrbuf->page_base;
		seg[n].mr_len = min_t(u32,
			PAGE_SIZE - xdrbuf->page_base, xdrbuf->page_len);
		len = xdrbuf->page_len - seg[n].mr_len;
		++n;
		p = 1;
		while (len > 0) {
			if (n == nsegs)
				return 0;
			seg[n].mr_page = xdrbuf->pages[p];
			seg[n].mr_offset = NULL;
			seg[n].mr_len = min_t(u32, PAGE_SIZE, len);
			len -= seg[n].mr_len;
			++n;
			++p;
		}
	}

	if (xdrbuf->tail[0].iov_len) {
		if (n == nsegs)
			return 0;
		seg[n].mr_page = NULL;
		seg[n].mr_offset = xdrbuf->tail[0].iov_base;
		seg[n].mr_len = xdrbuf->tail[0].iov_len;
		++n;
	}

	return n;
}

/*
 * Create read/write chunk lists, and reply chunks, for RDMA
 *
 *   Assume check against THRESHOLD has been done, and chunks are required.
 *   Assume only encoding one list entry for read|write chunks. The NFSv3
 *     protocol is simple enough to allow this as it only has a single "bulk
 *     result" in each procedure - complicated NFSv4 COMPOUNDs are not. (The
 *     RDMA/Sessions NFSv4 proposal addresses this for future v4 revs.)
 *
 * When used for a single reply chunk (which is a special write
 * chunk used for the entire reply, rather than just the data), it
 * is used primarily for READDIR and READLINK which would otherwise
 * be severely size-limited by a small rdma inline read max. The server
 * response will come back as an RDMA Write, followed by a message
 * of type RDMA_NOMSG carrying the xid and length. As a result, reply
 * chunks do not provide data alignment, however they do not require
 * "fixup" (moving the response to the upper layer buffer) either.
 *
 * Encoding key for single-list chunks (HLOO = Handle32 Length32 Offset64):
 *
 *  Read chunklist (a linked list):
 *   N elements, position P (same P for all chunks of same arg!):
 *    1 - PHLOO - 1 - PHLOO - ... - 1 - PHLOO - 0
 *
 *  Write chunklist (a list of (one) counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO - 0
 *
 *  Reply chunk (a counted array):
 *   N elements:
 *    1 - N - HLOO - HLOO - ... - HLOO
 */

static unsigned int
rpcrdma_create_chunks(struct rpc_rqst *rqst, struct xdr_buf *target,
		struct rpcrdma_msg *headerp, enum rpcrdma_chunktype type)
{
	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_task->tk_xprt);
	int nsegs, nchunks = 0;
	int pos;
	struct rpcrdma_mr_seg *seg = req->rl_segments;
	struct rpcrdma_read_chunk *cur_rchunk = NULL;
	struct rpcrdma_write_array *warray = NULL;
	struct rpcrdma_write_chunk *cur_wchunk = NULL;
	__be32 *iptr = headerp->rm_body.rm_chunks;

	if (type == rpcrdma_readch || type == rpcrdma_areadch) {
		/* a read chunk - server will RDMA Read our memory */
		cur_rchunk = (struct rpcrdma_read_chunk *) iptr;
	} else {
		/* a write or reply chunk - server will RDMA Write our memory */
		*iptr++ = xdr_zero;	/* encode a NULL read chunk list */
		if (type == rpcrdma_replych)
			*iptr++ = xdr_zero;	/* a NULL write chunk list */
		warray = (struct rpcrdma_write_array *) iptr;
		cur_wchunk = (struct rpcrdma_write_chunk *) (warray + 1);
	}

	if (type == rpcrdma_replych || type == rpcrdma_areadch)
		pos = 0;
	else
		pos = target->head[0].iov_len;

	nsegs = rpcrdma_convert_iovs(target, pos, type, seg, RPCRDMA_MAX_SEGS);
	if (nsegs == 0)
		return 0;

	do {
		/* bind/register the memory, then build chunk from result. */
		int n = rpcrdma_register_external(seg, nsegs,
						cur_wchunk != NULL, r_xprt);
		if (n <= 0)
			goto out;
		if (cur_rchunk) {	/* read */
			cur_rchunk->rc_discrim = xdr_one;
			/* all read chunks have the same "position" */
			cur_rchunk->rc_position = htonl(pos);
			cur_rchunk->rc_target.rs_handle = htonl(seg->mr_rkey);
			cur_rchunk->rc_target.rs_length = htonl(seg->mr_len);
			xdr_encode_hyper(
					(__be32 *)&cur_rchunk->rc_target.rs_offset,
					seg->mr_base);
			dprintk("RPC:       %s: read chunk "
				"elem %d@0x%llx:0x%x pos %d (%s)\n", __func__,
				seg->mr_len, (unsigned long long)seg->mr_base,
				seg->mr_rkey, pos, n < nsegs ? "more" : "last");
			cur_rchunk++;
			r_xprt->rx_stats.read_chunk_count++;
		} else {		/* write/reply */
			cur_wchunk->wc_target.rs_handle = htonl(seg->mr_rkey);
			cur_wchunk->wc_target.rs_length = htonl(seg->mr_len);
			xdr_encode_hyper(
					(__be32 *)&cur_wchunk->wc_target.rs_offset,
					seg->mr_base);
			dprintk("RPC:       %s: %s chunk "
				"elem %d@0x%llx:0x%x (%s)\n", __func__,
				(type == rpcrdma_replych) ? "reply" : "write",
				seg->mr_len, (unsigned long long)seg->mr_base,
				seg->mr_rkey, n < nsegs ? "more" : "last");
			cur_wchunk++;
			if (type == rpcrdma_replych)
				r_xprt->rx_stats.reply_chunk_count++;
			else
				r_xprt->rx_stats.write_chunk_count++;
			r_xprt->rx_stats.total_rdma_request += seg->mr_len;
		}
		nchunks++;
		seg   += n;
		nsegs -= n;
	} while (nsegs);

	/* success. all failures return above */
	req->rl_nchunks = nchunks;

	BUG_ON(nchunks == 0);

	/*
	 * finish off header. If write, marshal discrim and nchunks.
	 */
	if (cur_rchunk) {
		iptr = (__be32 *) cur_rchunk;
		*iptr++ = xdr_zero;	/* finish the read chunk list */
		*iptr++ = xdr_zero;	/* encode a NULL write chunk list */
		*iptr++ = xdr_zero;	/* encode a NULL reply chunk */
	} else {
		warray->wc_discrim = xdr_one;
		warray->wc_nchunks = htonl(nchunks);
		iptr = (__be32 *) cur_wchunk;
		if (type == rpcrdma_writech) {
			*iptr++ = xdr_zero; /* finish the write chunk list */
			*iptr++ = xdr_zero; /* encode a NULL reply chunk */
		}
	}

	/*
	 * Return header size.
	 */
	return (unsigned char *)iptr - (unsigned char *)headerp;

out:
	for (pos = 0; nchunks--;)
		pos += rpcrdma_deregister_external(
				&req->rl_segments[pos], r_xprt, NULL);
	return 0;
}

/*
 * Copy write data inline.
 * This function is used for "small" requests. Data which is passed
 * to RPC via iovecs (or page list) is copied directly into the
 * pre-registered memory buffer for this request. For small amounts
 * of data, this is efficient. The cutoff value is tunable.
 */
static int
rpcrdma_inline_pullup(struct rpc_rqst *rqst, int pad)
{
	int i, npages, curlen;
	int copy_len;
	unsigned char *srcp, *destp;
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);

	destp = rqst->rq_svec[0].iov_base;
	curlen = rqst->rq_svec[0].iov_len;
	destp += curlen;
	/*
	 * Do optional padding where it makes sense. Alignment of write
	 * payload can help the server, if our setting is accurate.
	 */
	pad -= (curlen + 36/*sizeof(struct rpcrdma_msg_padded)*/);
	if (pad < 0 || rqst->rq_slen - curlen < RPCRDMA_INLINE_PAD_THRESH)
		pad = 0;	/* don't pad this request */

	dprintk("RPC:       %s: pad %d destp 0x%p len %d hdrlen %d\n",
		__func__, pad, destp, rqst->rq_slen, curlen);

	copy_len = rqst->rq_snd_buf.page_len;
	r_xprt->rx_stats.pullup_copy_count += copy_len;
	npages = PAGE_ALIGN(rqst->rq_snd_buf.page_base+copy_len) >> PAGE_SHIFT;
	for (i = 0; copy_len && i < npages; i++) {
		if (i == 0)
			curlen = PAGE_SIZE - rqst->rq_snd_buf.page_base;
		else
			curlen = PAGE_SIZE;
		if (curlen > copy_len)
			curlen = copy_len;
		dprintk("RPC:       %s: page %d destp 0x%p len %d curlen %d\n",
			__func__, i, destp, copy_len, curlen);
		srcp = kmap_atomic(rqst->rq_snd_buf.pages[i],
					KM_SKB_SUNRPC_DATA);
		if (i == 0)
			memcpy(destp, srcp+rqst->rq_snd_buf.page_base, curlen);
		else
			memcpy(destp, srcp, curlen);
		kunmap_atomic(srcp, KM_SKB_SUNRPC_DATA);
		rqst->rq_svec[0].iov_len += curlen;
		destp += curlen;
		copy_len -= curlen;
	}
	if (rqst->rq_snd_buf.tail[0].iov_len) {
		curlen = rqst->rq_snd_buf.tail[0].iov_len;
		if (destp != rqst->rq_snd_buf.tail[0].iov_base) {
			memcpy(destp,
				rqst->rq_snd_buf.tail[0].iov_base, curlen);
			r_xprt->rx_stats.pullup_copy_count += curlen;
		}
		dprintk("RPC:       %s: tail destp 0x%p len %d curlen %d\n",
			__func__, destp, copy_len, curlen);
		rqst->rq_svec[0].iov_len += curlen;
	}
	/* header now contains entire send message */
	return pad;
}

/*
 * Marshal a request: the primary job of this routine is to choose
 * the transfer modes. See comments below.
 *
 * Uses multiple RDMA IOVs for a request:
 *  [0] -- RPC RDMA header, which uses memory from the *start* of the
 *         preregistered buffer that already holds the RPC data in
 *         its middle.
 *  [1] -- the RPC header/data, marshaled by RPC and the NFS protocol.
 *  [2] -- optional padding.
 *  [3] -- if padded, header only in [1] and data here.
 */

int
rpcrdma_marshal_req(struct rpc_rqst *rqst)
{
	struct rpc_xprt *xprt = rqst->rq_task->tk_xprt;
	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
	char *base;
	size_t hdrlen, rpclen, padlen;
	enum rpcrdma_chunktype rtype, wtype;
	struct rpcrdma_msg *headerp;

	/*
	 * rpclen gets amount of data in first buffer, which is the
	 * pre-registered buffer.
	 */
	base = rqst->rq_svec[0].iov_base;
	rpclen = rqst->rq_svec[0].iov_len;

	/* build RDMA header in private area at front */
	headerp = (struct rpcrdma_msg *) req->rl_base;
	/* don't htonl XID, it's already done in request */
	headerp->rm_xid = rqst->rq_xid;
	headerp->rm_vers = xdr_one;
	headerp->rm_credit = htonl(r_xprt->rx_buf.rb_max_requests);
	headerp->rm_type = __constant_htonl(RDMA_MSG);

	/*
	 * Chunks needed for results?
	 *
	 * o If the expected result is under the inline threshold, all ops
	 *   return as inline (but see later).
	 * o Large non-read ops return as a single reply chunk.
	 * o Large read ops return data as write chunk(s), header as inline.
	 *
	 * Note: the NFS code sending down multiple result segments implies
	 * the op is one of read, readdir[plus], readlink or NFSv4 getacl.
	 */

	/*
	 * This code can handle read chunks, write chunks OR reply
	 * chunks -- only one type. If the request is too big to fit
	 * inline, then we will choose read chunks. If the request is
	 * a READ, then use write chunks to separate the file data
	 * into pages; otherwise use reply chunks.
	 */
	if (rqst->rq_rcv_buf.buflen <= RPCRDMA_INLINE_READ_THRESHOLD(rqst))
		wtype = rpcrdma_noch;
	else if (rqst->rq_rcv_buf.page_len == 0)
		wtype = rpcrdma_replych;
	else if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
		wtype = rpcrdma_writech;
	else
		wtype = rpcrdma_replych;

	/*
	 * Chunks needed for arguments?
	 *
	 * 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.
	 *
	 * Note: the NFS code sending down multiple argument segments
	 * implies the op is a write.
	 * TBD check NFSv4 setacl
	 */
	if (rqst->rq_snd_buf.len <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst))
		rtype = rpcrdma_noch;
	else if (rqst->rq_snd_buf.page_len == 0)
		rtype = rpcrdma_areadch;
	else