net/rds/message.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (c) 2006 Oracle.  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
  * OpenIB.org BSD 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.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
  */
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/export.h>

 #include "rds.h"

 static unsigned int	rds_exthdr_size[__RDS_EXTHDR_MAX] = {
 [RDS_EXTHDR_NONE]	= 0,
 [RDS_EXTHDR_VERSION]	= sizeof(struct rds_ext_header_version),
 [RDS_EXTHDR_RDMA]	= sizeof(struct rds_ext_header_rdma),
 [RDS_EXTHDR_RDMA_DEST]	= sizeof(struct rds_ext_header_rdma_dest),
 [RDS_EXTHDR_NPATHS]	= sizeof(u16),
 [RDS_EXTHDR_GEN_NUM]	= sizeof(u32),
 };


 void rds_message_addref(struct rds_message *rm)
 {
 	rdsdebug("addref rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
 	atomic_inc(&rm->m_refcount);
 }
 EXPORT_SYMBOL_GPL(rds_message_addref);

 /*
  * This relies on dma_map_sg() not touching sg[].page during merging.
  */
 static void rds_message_purge(struct rds_message *rm)
 {
 	unsigned long i;

 	if (unlikely(test_bit(RDS_MSG_PAGEVEC, &rm->m_flags)))
 		return;

 	for (i = 0; i < rm->data.op_nents; i++) {
 		rdsdebug("putting data page %p\n", (void *)sg_page(&rm->data.op_sg[i]));
 		/* XXX will have to put_page for page refs */
 		__free_page(sg_page(&rm->data.op_sg[i]));
 	}
 	rm->data.op_nents = 0;

 	if (rm->rdma.op_active)
 		rds_rdma_free_op(&rm->rdma);
 	if (rm->rdma.op_rdma_mr)
 		rds_mr_put(rm->rdma.op_rdma_mr);

 	if (rm->atomic.op_active)
 		rds_atomic_free_op(&rm->atomic);
 	if (rm->atomic.op_rdma_mr)
 		rds_mr_put(rm->atomic.op_rdma_mr);
 }

 void rds_message_put(struct rds_message *rm)
 {
 	rdsdebug("put rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
 	WARN(!atomic_read(&rm->m_refcount), "danger refcount zero on %p\n", rm);
 	if (atomic_dec_and_test(&rm->m_refcount)) {
 		BUG_ON(!list_empty(&rm->m_sock_item));
 		BUG_ON(!list_empty(&rm->m_conn_item));
 		rds_message_purge(rm);

 		kfree(rm);
 	}
 }
 EXPORT_SYMBOL_GPL(rds_message_put);

 void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
 				 __be16 dport, u64 seq)
 {
 	hdr->h_flags = 0;
 	hdr->h_sport = sport;
 	hdr->h_dport = dport;
 	hdr->h_sequence = cpu_to_be64(seq);
 	hdr->h_exthdr[0] = RDS_EXTHDR_NONE;
 }
 EXPORT_SYMBOL_GPL(rds_message_populate_header);

 int rds_message_add_extension(struct rds_header *hdr, unsigned int type,
 			      const void *data, unsigned int len)
 {
 	unsigned int ext_len = sizeof(u8) + len;
 	unsigned char *dst;

 	/* For now, refuse to add more than one extension header */
 	if (hdr->h_exthdr[0] != RDS_EXTHDR_NONE)
 		return 0;

 	if (type >= __RDS_EXTHDR_MAX || len != rds_exthdr_size[type])
 		return 0;

 	if (ext_len >= RDS_HEADER_EXT_SPACE)
 		return 0;
 	dst = hdr->h_exthdr;

 	*dst++ = type;
 	memcpy(dst, data, len);

 	dst[len] = RDS_EXTHDR_NONE;
 	return 1;
 }
 EXPORT_SYMBOL_GPL(rds_message_add_extension);

 /*
  * If a message has extension headers, retrieve them here.
  * Call like this:
  *
  * unsigned int pos = 0;
  *
  * while (1) {
  *	buflen = sizeof(buffer);
  *	type = rds_message_next_extension(hdr, &pos, buffer, &buflen);
  *	if (type == RDS_EXTHDR_NONE)
  *		break;
  *	...
  * }
  */
 int rds_message_next_extension(struct rds_header *hdr,
 		unsigned int *pos, void *buf, unsigned int *buflen)
 {
 	unsigned int offset, ext_type, ext_len;
 	u8 *src = hdr->h_exthdr;

 	offset = *pos;
 	if (offset >= RDS_HEADER_EXT_SPACE)
 		goto none;

 	/* Get the extension type and length. For now, the
 	 * length is implied by the extension type. */
 	ext_type = src[offset++];

 	if (ext_type == RDS_EXTHDR_NONE || ext_type >= __RDS_EXTHDR_MAX)
 		goto none;
 	ext_len = rds_exthdr_size[ext_type];
 	if (offset + ext_len > RDS_HEADER_EXT_SPACE)
 		goto none;

 	*pos = offset + ext_len;
 	if (ext_len < *buflen)
 		*buflen = ext_len;
 	memcpy(buf, src + offset, *buflen);
 	return ext_type;

 none:
 	*pos = RDS_HEADER_EXT_SPACE;
 	*buflen = 0;
 	return RDS_EXTHDR_NONE;
 }

 int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 offset)
 {
 	struct rds_ext_header_rdma_dest ext_hdr;

 	ext_hdr.h_rdma_rkey = cpu_to_be32(r_key);
 	ext_hdr.h_rdma_offset = cpu_to_be32(offset);
 	return rds_message_add_extension(hdr, RDS_EXTHDR_RDMA_DEST, &ext_hdr, sizeof(ext_hdr));
 }
 EXPORT_SYMBOL_GPL(rds_message_add_rdma_dest_extension);

 /*
  * Each rds_message is allocated with extra space for the scatterlist entries
  * rds ops will need. This is to minimize memory allocation count. Then, each rds op
  * can grab SGs when initializing its part of the rds_message.
  */
 struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
 {
 	struct rds_message *rm;

 	if (extra_len > KMALLOC_MAX_SIZE - sizeof(struct rds_message))
 		return NULL;

 	rm = kzalloc(sizeof(struct rds_message) + extra_len, gfp);
 	if (!rm)
 		goto out;

 	rm->m_used_sgs = 0;
 	rm->m_total_sgs = extra_len / sizeof(struct scatterlist);

 	atomic_set(&rm->m_refcount, 1);
 	INIT_LIST_HEAD(&rm->m_sock_item);
 	INIT_LIST_HEAD(&rm->m_conn_item);
 	spin_lock_init(&rm->m_rs_lock);
 	init_waitqueue_head(&rm->m_flush_wait);

 out:
 	return rm;
 }

 /*
  * RDS ops use this to grab SG entries from the rm's sg pool.
  */
 struct scatterlist *rds_message_alloc_sgs(struct rds_message *rm, int nents)
 {
 	struct scatterlist *sg_first = (struct scatterlist *) &rm[1];
 	struct scatterlist *sg_ret;

 	WARN_ON(rm->m_used_sgs + nents > rm->m_total_sgs);
 	WARN_ON(!nents);

 	if (rm->m_used_sgs + nents > rm->m_total_sgs)
 		return NULL;

 	sg_ret = &sg_first[rm->m_used_sgs];
 	sg_init_table(sg_ret, nents);
 	rm->m_used_sgs += nents;

 	return sg_ret;
 }

 struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned int total_len)
 {
 	struct rds_message *rm;
 	unsigned int i;
 	int num_sgs = ceil(total_len, PAGE_SIZE);
 	int extra_bytes = num_sgs * sizeof(struct scatterlist);

 	rm = rds_message_alloc(extra_bytes, GFP_NOWAIT);
 	if (!rm)
 		return ERR_PTR(-ENOMEM);

 	set_bit(RDS_MSG_PAGEVEC, &rm->m_flags);
 	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
 	rm->data.op_nents = ceil(total_len, PAGE_SIZE);
 	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
 	if (!rm->data.op_sg) {
 		rds_message_put(rm);
 		return ERR_PTR(-ENOMEM);
 	}

 	for (i = 0; i < rm->data.op_nents; ++i) {
 		sg_set_page(&rm->data.op_sg[i],
 				virt_to_page(page_addrs[i]),
 				PAGE_SIZE, 0);
 	}

 	return rm;
 }

 int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from)
 {
 	unsigned long to_copy, nbytes;
 	unsigned long sg_off;
 	struct scatterlist *sg;
 	int ret = 0;

 	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));

 	/*
 	 * now allocate and copy in the data payload.
 	 */
 	sg = rm->data.op_sg;
 	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */

 	while (iov_iter_count(from)) {
 		if (!sg_page(sg)) {
 			ret = rds_page_remainder_alloc(sg, iov_iter_count(from),
 						       GFP_HIGHUSER);
 			if (ret)
 				return ret;
 			rm->data.op_nents++;
 			sg_off = 0;
 		}

 		to_copy = min_t(unsigned long, iov_iter_count(from),
 				sg->length - sg_off);

 		rds_stats_add(s_copy_from_user, to_copy);
 		nbytes = copy_page_from_iter(sg_page(sg), sg->offset + sg_off,
 					     to_copy, from);
 		if (nbytes != to_copy)
 			return -EFAULT;

 		sg_off += to_copy;

 		if (sg_off == sg->length)
 			sg++;
 	}

 	return ret;
 }

 int rds_message_inc_copy_to_user(struct rds_incoming *inc, struct iov_iter *to)
 {
 	struct rds_message *rm;
 	struct scatterlist *sg;
 	unsigned long to_copy;
 	unsigned long vec_off;
 	int copied;
 	int ret;
 	u32 len;

 	rm = container_of(inc, struct rds_message, m_inc);
 	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);

 	sg = rm->data.op_sg;
 	vec_off = 0;
 	copied = 0;

 	while (iov_iter_count(to) && copied < len) {
 		to_copy = min_t(unsigned long, iov_iter_count(to),
 				sg->length - vec_off);
 		to_copy = min_t(unsigned long, to_copy, len - copied);

 		rds_stats_add(s_copy_to_user, to_copy);
 		ret = copy_page_to_iter(sg_page(sg), sg->offset + vec_off,
 					to_copy, to);
 		if (ret != to_copy)
 			return -EFAULT;

 		vec_off += to_copy;
 		copied += to_copy;

 		if (vec_off == sg->length) {
 			vec_off = 0;
 			sg++;
 		}
 	}

 	return copied;
 }

 /*
  * If the message is still on the send queue, wait until the transport
  * is done with it. This is particularly important for RDMA operations.
  */
 void rds_message_wait(struct rds_message *rm)
 {
 	wait_event_interruptible(rm->m_flush_wait,
 			!test_bit(RDS_MSG_MAPPED, &rm->m_flags));
 }

 void rds_message_unmapped(struct rds_message *rm)
 {
 	clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
 	wake_up_interruptible(&rm->m_flush_wait);
 }
 EXPORT_SYMBOL_GPL(rds_message_unmapped);
	/*
	* Copyright (c) 2006 Oracle. 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
	* OpenIB.org BSD 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.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
	* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
	* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	* SOFTWARE.
	*
	*/
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/export.h>

	#include "rds.h"

	static unsigned int rds_exthdr_size[__RDS_EXTHDR_MAX] = {
	[RDS_EXTHDR_NONE] = 0,
	[RDS_EXTHDR_VERSION] = sizeof(struct rds_ext_header_version),
	[RDS_EXTHDR_RDMA] = sizeof(struct rds_ext_header_rdma),
	[RDS_EXTHDR_RDMA_DEST] = sizeof(struct rds_ext_header_rdma_dest),
	[RDS_EXTHDR_NPATHS] = sizeof(u16),
	[RDS_EXTHDR_GEN_NUM] = sizeof(u32),
	};


	void rds_message_addref(struct rds_message *rm)
	{
	rdsdebug("addref rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
	atomic_inc(&rm->m_refcount);
	}
	EXPORT_SYMBOL_GPL(rds_message_addref);

	/*
	* This relies on dma_map_sg() not touching sg[].page during merging.
	*/
	static void rds_message_purge(struct rds_message *rm)
	{
	unsigned long i;

	if (unlikely(test_bit(RDS_MSG_PAGEVEC, &rm->m_flags)))
	return;

	for (i = 0; i < rm->data.op_nents; i++) {
	rdsdebug("putting data page %p\n", (void *)sg_page(&rm->data.op_sg[i]));
	/* XXX will have to put_page for page refs */
	__free_page(sg_page(&rm->data.op_sg[i]));
	}
	rm->data.op_nents = 0;

	if (rm->rdma.op_active)
	rds_rdma_free_op(&rm->rdma);
	if (rm->rdma.op_rdma_mr)
	rds_mr_put(rm->rdma.op_rdma_mr);

	if (rm->atomic.op_active)
	rds_atomic_free_op(&rm->atomic);
	if (rm->atomic.op_rdma_mr)
	rds_mr_put(rm->atomic.op_rdma_mr);
	}

	void rds_message_put(struct rds_message *rm)
	{
	rdsdebug("put rm %p ref %d\n", rm, atomic_read(&rm->m_refcount));
	WARN(!atomic_read(&rm->m_refcount), "danger refcount zero on %p\n", rm);
	if (atomic_dec_and_test(&rm->m_refcount)) {
	BUG_ON(!list_empty(&rm->m_sock_item));
	BUG_ON(!list_empty(&rm->m_conn_item));
	rds_message_purge(rm);

	kfree(rm);
	}
	}
	EXPORT_SYMBOL_GPL(rds_message_put);

	void rds_message_populate_header(struct rds_header *hdr, __be16 sport,
	__be16 dport, u64 seq)
	{
	hdr->h_flags = 0;
	hdr->h_sport = sport;
	hdr->h_dport = dport;
	hdr->h_sequence = cpu_to_be64(seq);
	hdr->h_exthdr[0] = RDS_EXTHDR_NONE;
	}
	EXPORT_SYMBOL_GPL(rds_message_populate_header);

	int rds_message_add_extension(struct rds_header *hdr, unsigned int type,
	const void *data, unsigned int len)
	{
	unsigned int ext_len = sizeof(u8) + len;
	unsigned char *dst;

	/* For now, refuse to add more than one extension header */
	if (hdr->h_exthdr[0] != RDS_EXTHDR_NONE)
	return 0;

	if (type >= __RDS_EXTHDR_MAX \|\| len != rds_exthdr_size[type])
	return 0;

	if (ext_len >= RDS_HEADER_EXT_SPACE)
	return 0;
	dst = hdr->h_exthdr;

	*dst++ = type;
	memcpy(dst, data, len);

	dst[len] = RDS_EXTHDR_NONE;
	return 1;
	}
	EXPORT_SYMBOL_GPL(rds_message_add_extension);

	/*
	* If a message has extension headers, retrieve them here.
	* Call like this:
	*
	* unsigned int pos = 0;
	*
	* while (1) {
	* buflen = sizeof(buffer);
	* type = rds_message_next_extension(hdr, &pos, buffer, &buflen);
	* if (type == RDS_EXTHDR_NONE)
	* break;
	* ...
	* }
	*/
	int rds_message_next_extension(struct rds_header *hdr,
	unsigned int pos, void buf, unsigned int *buflen)
	{
	unsigned int offset, ext_type, ext_len;
	u8 *src = hdr->h_exthdr;

	offset = *pos;
	if (offset >= RDS_HEADER_EXT_SPACE)
	goto none;

	/* Get the extension type and length. For now, the
	* length is implied by the extension type. */
	ext_type = src[offset++];

	if (ext_type == RDS_EXTHDR_NONE \|\| ext_type >= __RDS_EXTHDR_MAX)
	goto none;
	ext_len = rds_exthdr_size[ext_type];
	if (offset + ext_len > RDS_HEADER_EXT_SPACE)
	goto none;

	*pos = offset + ext_len;
	if (ext_len < *buflen)
	*buflen = ext_len;
	memcpy(buf, src + offset, *buflen);
	return ext_type;

	none:
	*pos = RDS_HEADER_EXT_SPACE;
	*buflen = 0;
	return RDS_EXTHDR_NONE;
	}

	int rds_message_add_rdma_dest_extension(struct rds_header *hdr, u32 r_key, u32 offset)
	{
	struct rds_ext_header_rdma_dest ext_hdr;

	ext_hdr.h_rdma_rkey = cpu_to_be32(r_key);
	ext_hdr.h_rdma_offset = cpu_to_be32(offset);
	return rds_message_add_extension(hdr, RDS_EXTHDR_RDMA_DEST, &ext_hdr, sizeof(ext_hdr));
	}
	EXPORT_SYMBOL_GPL(rds_message_add_rdma_dest_extension);

	/*
	* Each rds_message is allocated with extra space for the scatterlist entries
	* rds ops will need. This is to minimize memory allocation count. Then, each rds op
	* can grab SGs when initializing its part of the rds_message.
	*/
	struct rds_message *rds_message_alloc(unsigned int extra_len, gfp_t gfp)
	{
	struct rds_message *rm;

	if (extra_len > KMALLOC_MAX_SIZE - sizeof(struct rds_message))
	return NULL;

	rm = kzalloc(sizeof(struct rds_message) + extra_len, gfp);
	if (!rm)
	goto out;

	rm->m_used_sgs = 0;
	rm->m_total_sgs = extra_len / sizeof(struct scatterlist);

	atomic_set(&rm->m_refcount, 1);
	INIT_LIST_HEAD(&rm->m_sock_item);
	INIT_LIST_HEAD(&rm->m_conn_item);
	spin_lock_init(&rm->m_rs_lock);
	init_waitqueue_head(&rm->m_flush_wait);

	out:
	return rm;
	}

	/*
	* RDS ops use this to grab SG entries from the rm's sg pool.
	*/
	struct scatterlist rds_message_alloc_sgs(struct rds_message rm, int nents)
	{
	struct scatterlist sg_first = (struct scatterlist ) &rm[1];
	struct scatterlist *sg_ret;

	WARN_ON(rm->m_used_sgs + nents > rm->m_total_sgs);
	WARN_ON(!nents);

	if (rm->m_used_sgs + nents > rm->m_total_sgs)
	return NULL;

	sg_ret = &sg_first[rm->m_used_sgs];
	sg_init_table(sg_ret, nents);
	rm->m_used_sgs += nents;

	return sg_ret;
	}

	struct rds_message rds_message_map_pages(unsigned long page_addrs, unsigned int total_len)
	{
	struct rds_message *rm;
	unsigned int i;
	int num_sgs = ceil(total_len, PAGE_SIZE);
	int extra_bytes = num_sgs * sizeof(struct scatterlist);

	rm = rds_message_alloc(extra_bytes, GFP_NOWAIT);
	if (!rm)
	return ERR_PTR(-ENOMEM);

	set_bit(RDS_MSG_PAGEVEC, &rm->m_flags);
	rm->m_inc.i_hdr.h_len = cpu_to_be32(total_len);
	rm->data.op_nents = ceil(total_len, PAGE_SIZE);
	rm->data.op_sg = rds_message_alloc_sgs(rm, num_sgs);
	if (!rm->data.op_sg) {
	rds_message_put(rm);
	return ERR_PTR(-ENOMEM);
	}

	for (i = 0; i < rm->data.op_nents; ++i) {
	sg_set_page(&rm->data.op_sg[i],
	virt_to_page(page_addrs[i]),
	PAGE_SIZE, 0);
	}

	return rm;
	}

	int rds_message_copy_from_user(struct rds_message rm, struct iov_iter from)
	{
	unsigned long to_copy, nbytes;
	unsigned long sg_off;
	struct scatterlist *sg;
	int ret = 0;

	rm->m_inc.i_hdr.h_len = cpu_to_be32(iov_iter_count(from));

	/*
	* now allocate and copy in the data payload.
	*/
	sg = rm->data.op_sg;
	sg_off = 0; /* Dear gcc, sg->page will be null from kzalloc. */

	while (iov_iter_count(from)) {
	if (!sg_page(sg)) {
	ret = rds_page_remainder_alloc(sg, iov_iter_count(from),
	GFP_HIGHUSER);
	if (ret)
	return ret;
	rm->data.op_nents++;
	sg_off = 0;
	}

	to_copy = min_t(unsigned long, iov_iter_count(from),
	sg->length - sg_off);

	rds_stats_add(s_copy_from_user, to_copy);
	nbytes = copy_page_from_iter(sg_page(sg), sg->offset + sg_off,
	to_copy, from);
	if (nbytes != to_copy)
	return -EFAULT;

	sg_off += to_copy;

	if (sg_off == sg->length)
	sg++;
	}

	return ret;
	}

	int rds_message_inc_copy_to_user(struct rds_incoming inc, struct iov_iter to)
	{
	struct rds_message *rm;
	struct scatterlist *sg;
	unsigned long to_copy;
	unsigned long vec_off;
	int copied;
	int ret;
	u32 len;

	rm = container_of(inc, struct rds_message, m_inc);
	len = be32_to_cpu(rm->m_inc.i_hdr.h_len);

	sg = rm->data.op_sg;
	vec_off = 0;
	copied = 0;

	while (iov_iter_count(to) && copied < len) {
	to_copy = min_t(unsigned long, iov_iter_count(to),
	sg->length - vec_off);
	to_copy = min_t(unsigned long, to_copy, len - copied);

	rds_stats_add(s_copy_to_user, to_copy);
	ret = copy_page_to_iter(sg_page(sg), sg->offset + vec_off,
	to_copy, to);
	if (ret != to_copy)
	return -EFAULT;

	vec_off += to_copy;
	copied += to_copy;

	if (vec_off == sg->length) {
	vec_off = 0;
	sg++;
	}
	}

	return copied;
	}

	/*
	* If the message is still on the send queue, wait until the transport
	* is done with it. This is particularly important for RDMA operations.
	*/
	void rds_message_wait(struct rds_message *rm)
	{
	wait_event_interruptible(rm->m_flush_wait,
	!test_bit(RDS_MSG_MAPPED, &rm->m_flags));
	}

	void rds_message_unmapped(struct rds_message *rm)
	{
	clear_bit(RDS_MSG_MAPPED, &rm->m_flags);
	wake_up_interruptible(&rm->m_flush_wait);
	}
	EXPORT_SYMBOL_GPL(rds_message_unmapped);