drivers/infiniband/ulp/iser/iser_memory.c - maze/linux - Git at Google

 /*
  * Copyright (c) 2004, 2005, 2006 Voltaire, 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
  * 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/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/scatterlist.h>

 #include "iscsi_iser.h"

 #define ISER_KMALLOC_THRESHOLD 0x20000 /* 128K - kmalloc limit */

 /**
  * iser_start_rdma_unaligned_sg
  */
 static int iser_start_rdma_unaligned_sg(struct iscsi_iser_task *iser_task,
 					enum iser_data_dir cmd_dir)
 {
 	int dma_nents;
 	struct ib_device *dev;
 	char *mem = NULL;
 	struct iser_data_buf *data = &iser_task->data[cmd_dir];
 	unsigned long  cmd_data_len = data->data_len;

 	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
 		mem = (void *)__get_free_pages(GFP_ATOMIC,
 		      ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
 	else
 		mem = kmalloc(cmd_data_len, GFP_ATOMIC);

 	if (mem == NULL) {
 		iser_err("Failed to allocate mem size %d %d for copying sglist\n",
 			 data->size,(int)cmd_data_len);
 		return -ENOMEM;
 	}

 	if (cmd_dir == ISER_DIR_OUT) {
 		/* copy the unaligned sg the buffer which is used for RDMA */
 		struct scatterlist *sgl = (struct scatterlist *)data->buf;
 		struct scatterlist *sg;
 		int i;
 		char *p, *from;

 		p = mem;
 		for_each_sg(sgl, sg, data->size, i) {
 			from = kmap_atomic(sg_page(sg));
 			memcpy(p,
 			       from + sg->offset,
 			       sg->length);
 			kunmap_atomic(from);
 			p += sg->length;
 		}
 	}

 	sg_init_one(&iser_task->data_copy[cmd_dir].sg_single, mem, cmd_data_len);
 	iser_task->data_copy[cmd_dir].buf  =
 		&iser_task->data_copy[cmd_dir].sg_single;
 	iser_task->data_copy[cmd_dir].size = 1;

 	iser_task->data_copy[cmd_dir].copy_buf  = mem;

 	dev = iser_task->iser_conn->ib_conn->device->ib_device;
 	dma_nents = ib_dma_map_sg(dev,
 				  &iser_task->data_copy[cmd_dir].sg_single,
 				  1,
 				  (cmd_dir == ISER_DIR_OUT) ?
 				  DMA_TO_DEVICE : DMA_FROM_DEVICE);
 	BUG_ON(dma_nents == 0);

 	iser_task->data_copy[cmd_dir].dma_nents = dma_nents;
 	return 0;
 }

 /**
  * iser_finalize_rdma_unaligned_sg
  */
 void iser_finalize_rdma_unaligned_sg(struct iscsi_iser_task *iser_task,
 				     enum iser_data_dir         cmd_dir)
 {
 	struct ib_device *dev;
 	struct iser_data_buf *mem_copy;
 	unsigned long  cmd_data_len;

 	dev = iser_task->iser_conn->ib_conn->device->ib_device;
 	mem_copy = &iser_task->data_copy[cmd_dir];

 	ib_dma_unmap_sg(dev, &mem_copy->sg_single, 1,
 			(cmd_dir == ISER_DIR_OUT) ?
 			DMA_TO_DEVICE : DMA_FROM_DEVICE);

 	if (cmd_dir == ISER_DIR_IN) {
 		char *mem;
 		struct scatterlist *sgl, *sg;
 		unsigned char *p, *to;
 		unsigned int sg_size;
 		int i;

 		/* copy back read RDMA to unaligned sg */
 		mem	= mem_copy->copy_buf;

 		sgl	= (struct scatterlist *)iser_task->data[ISER_DIR_IN].buf;
 		sg_size = iser_task->data[ISER_DIR_IN].size;

 		p = mem;
 		for_each_sg(sgl, sg, sg_size, i) {
 			to = kmap_atomic(sg_page(sg));
 			memcpy(to + sg->offset,
 			       p,
 			       sg->length);
 			kunmap_atomic(to);
 			p += sg->length;
 		}
 	}

 	cmd_data_len = iser_task->data[cmd_dir].data_len;

 	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
 		free_pages((unsigned long)mem_copy->copy_buf,
 			   ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
 	else
 		kfree(mem_copy->copy_buf);

 	mem_copy->copy_buf = NULL;
 }

 #define IS_4K_ALIGNED(addr)	((((unsigned long)addr) & ~MASK_4K) == 0)

 /**
  * iser_sg_to_page_vec - Translates scatterlist entries to physical addresses
  * and returns the length of resulting physical address array (may be less than
  * the original due to possible compaction).
  *
  * we build a "page vec" under the assumption that the SG meets the RDMA
  * alignment requirements. Other then the first and last SG elements, all
  * the "internal" elements can be compacted into a list whose elements are
  * dma addresses of physical pages. The code supports also the weird case
  * where --few fragments of the same page-- are present in the SG as
  * consecutive elements. Also, it handles one entry SG.
  */

 static int iser_sg_to_page_vec(struct iser_data_buf *data,
 			       struct iser_page_vec *page_vec,
 			       struct ib_device *ibdev)
 {
 	struct scatterlist *sg, *sgl = (struct scatterlist *)data->buf;
 	u64 start_addr, end_addr, page, chunk_start = 0;
 	unsigned long total_sz = 0;
 	unsigned int dma_len;
 	int i, new_chunk, cur_page, last_ent = data->dma_nents - 1;

 	/* compute the offset of first element */
 	page_vec->offset = (u64) sgl[0].offset & ~MASK_4K;

 	new_chunk = 1;
 	cur_page  = 0;
 	for_each_sg(sgl, sg, data->dma_nents, i) {
 		start_addr = ib_sg_dma_address(ibdev, sg);
 		if (new_chunk)
 			chunk_start = start_addr;
 		dma_len = ib_sg_dma_len(ibdev, sg);
 		end_addr = start_addr + dma_len;
 		total_sz += dma_len;

 		/* collect page fragments until aligned or end of SG list */
 		if (!IS_4K_ALIGNED(end_addr) && i < last_ent) {
 			new_chunk = 0;
 			continue;
 		}
 		new_chunk = 1;

 		/* address of the first page in the contiguous chunk;
 		   masking relevant for the very first SG entry,
 		   which might be unaligned */
 		page = chunk_start & MASK_4K;
 		do {
 			page_vec->pages[cur_page++] = page;
 			page += SIZE_4K;
 		} while (page < end_addr);
 	}

 	page_vec->data_size = total_sz;
 	iser_dbg("page_vec->data_size:%d cur_page %d\n", page_vec->data_size,cur_page);
 	return cur_page;
 }


 /**
  * iser_data_buf_aligned_len - Tries to determine the maximal correctly aligned
  * for RDMA sub-list of a scatter-gather list of memory buffers, and  returns
  * the number of entries which are aligned correctly. Supports the case where
  * consecutive SG elements are actually fragments of the same physcial page.
  */
 static int iser_data_buf_aligned_len(struct iser_data_buf *data,
 				      struct ib_device *ibdev)
 {
 	struct scatterlist *sgl, *sg, *next_sg = NULL;
 	u64 start_addr, end_addr;
 	int i, ret_len, start_check = 0;

 	if (data->dma_nents == 1)
 		return 1;

 	sgl = (struct scatterlist *)data->buf;
 	start_addr  = ib_sg_dma_address(ibdev, sgl);

 	for_each_sg(sgl, sg, data->dma_nents, i) {
 		if (start_check && !IS_4K_ALIGNED(start_addr))
 			break;

 		next_sg = sg_next(sg);
 		if (!next_sg)
 			break;

 		end_addr    = start_addr + ib_sg_dma_len(ibdev, sg);
 		start_addr  = ib_sg_dma_address(ibdev, next_sg);

 		if (end_addr == start_addr) {
 			start_check = 0;
 			continue;
 		} else
 			start_check = 1;

 		if (!IS_4K_ALIGNED(end_addr))
 			break;
 	}
 	ret_len = (next_sg) ? i : i+1;
 	iser_dbg("Found %d aligned entries out of %d in sg:0x%p\n",
 		 ret_len, data->dma_nents, data);
 	return ret_len;
 }

 static void iser_data_buf_dump(struct iser_data_buf *data,
 			       struct ib_device *ibdev)
 {
 	struct scatterlist *sgl = (struct scatterlist *)data->buf;
 	struct scatterlist *sg;
 	int i;

 	if (iser_debug_level == 0)
 		return;

 	for_each_sg(sgl, sg, data->dma_nents, i)
 		iser_warn("sg[%d] dma_addr:0x%lX page:0x%p "
 			 "off:0x%x sz:0x%x dma_len:0x%x\n",
 			 i, (unsigned long)ib_sg_dma_address(ibdev, sg),
 			 sg_page(sg), sg->offset,
 			 sg->length, ib_sg_dma_len(ibdev, sg));
 }

 static void iser_dump_page_vec(struct iser_page_vec *page_vec)
 {
 	int i;

 	iser_err("page vec length %d data size %d\n",
 		 page_vec->length, page_vec->data_size);
 	for (i = 0; i < page_vec->length; i++)
 		iser_err("%d %lx\n",i,(unsigned long)page_vec->pages[i]);
 }

 static void iser_page_vec_build(struct iser_data_buf *data,
 				struct iser_page_vec *page_vec,
 				struct ib_device *ibdev)
 {
 	int page_vec_len = 0;

 	page_vec->length = 0;
 	page_vec->offset = 0;

 	iser_dbg("Translating sg sz: %d\n", data->dma_nents);
 	page_vec_len = iser_sg_to_page_vec(data, page_vec, ibdev);
 	iser_dbg("sg len %d page_vec_len %d\n", data->dma_nents,page_vec_len);

 	page_vec->length = page_vec_len;

 	if (page_vec_len * SIZE_4K < page_vec->data_size) {
 		iser_err("page_vec too short to hold this SG\n");
 		iser_data_buf_dump(data, ibdev);
 		iser_dump_page_vec(page_vec);
 		BUG();
 	}
 }

 int iser_dma_map_task_data(struct iscsi_iser_task *iser_task,
 			    struct iser_data_buf *data,
 			    enum iser_data_dir iser_dir,
 			    enum dma_data_direction dma_dir)
 {
 	struct ib_device *dev;

 	iser_task->dir[iser_dir] = 1;
 	dev = iser_task->iser_conn->ib_conn->device->ib_device;

 	data->dma_nents = ib_dma_map_sg(dev, data->buf, data->size, dma_dir);
 	if (data->dma_nents == 0) {
 		iser_err("dma_map_sg failed!!!\n");
 		return -EINVAL;
 	}
 	return 0;
 }

 void iser_dma_unmap_task_data(struct iscsi_iser_task *iser_task)
 {
 	struct ib_device *dev;
 	struct iser_data_buf *data;

 	dev = iser_task->iser_conn->ib_conn->device->ib_device;

 	if (iser_task->dir[ISER_DIR_IN]) {
 		data = &iser_task->data[ISER_DIR_IN];
 		ib_dma_unmap_sg(dev, data->buf, data->size, DMA_FROM_DEVICE);
 	}

 	if (iser_task->dir[ISER_DIR_OUT]) {
 		data = &iser_task->data[ISER_DIR_OUT];
 		ib_dma_unmap_sg(dev, data->buf, data->size, DMA_TO_DEVICE);
 	}
 }

 /**
  * iser_reg_rdma_mem - Registers memory intended for RDMA,
  * obtaining rkey and va
  *
  * returns 0 on success, errno code on failure
  */
 int iser_reg_rdma_mem(struct iscsi_iser_task *iser_task,
 		      enum   iser_data_dir        cmd_dir)
 {
 	struct iscsi_conn    *iscsi_conn = iser_task->iser_conn->iscsi_conn;
 	struct iser_conn     *ib_conn = iser_task->iser_conn->ib_conn;
 	struct iser_device   *device = ib_conn->device;
 	struct ib_device     *ibdev = device->ib_device;
 	struct iser_data_buf *mem = &iser_task->data[cmd_dir];
 	struct iser_regd_buf *regd_buf;
 	int aligned_len;
 	int err;
 	int i;
 	struct scatterlist *sg;

 	regd_buf = &iser_task->rdma_regd[cmd_dir];

 	aligned_len = iser_data_buf_aligned_len(mem, ibdev);
 	if (aligned_len != mem->dma_nents) {
 		iscsi_conn->fmr_unalign_cnt++;
 		iser_warn("rdma alignment violation %d/%d aligned\n",
 			 aligned_len, mem->size);
 		iser_data_buf_dump(mem, ibdev);

 		/* unmap the command data before accessing it */
 		iser_dma_unmap_task_data(iser_task);

 		/* allocate copy buf, if we are writing, copy the */
 		/* unaligned scatterlist, dma map the copy        */
 		if (iser_start_rdma_unaligned_sg(iser_task, cmd_dir) != 0)
 				return -ENOMEM;
 		mem = &iser_task->data_copy[cmd_dir];
 	}

 	/* if there a single dma entry, FMR is not needed */
 	if (mem->dma_nents == 1) {
 		sg = (struct scatterlist *)mem->buf;

 		regd_buf->reg.lkey = device->mr->lkey;
 		regd_buf->reg.rkey = device->mr->rkey;
 		regd_buf->reg.len  = ib_sg_dma_len(ibdev, &sg[0]);
 		regd_buf->reg.va   = ib_sg_dma_address(ibdev, &sg[0]);
 		regd_buf->reg.is_fmr = 0;

 		iser_dbg("PHYSICAL Mem.register: lkey: 0x%08X rkey: 0x%08X  "
 			 "va: 0x%08lX sz: %ld]\n",
 			 (unsigned int)regd_buf->reg.lkey,
 			 (unsigned int)regd_buf->reg.rkey,
 			 (unsigned long)regd_buf->reg.va,
 			 (unsigned long)regd_buf->reg.len);
 	} else { /* use FMR for multiple dma entries */
 		iser_page_vec_build(mem, ib_conn->page_vec, ibdev);
 		err = iser_reg_page_vec(ib_conn, ib_conn->page_vec, &regd_buf->reg);
 		if (err) {
 			iser_data_buf_dump(mem, ibdev);
 			iser_err("mem->dma_nents = %d (dlength = 0x%x)\n",
 				 mem->dma_nents,
 				 ntoh24(iser_task->desc.iscsi_header.dlength));
 			iser_err("page_vec: data_size = 0x%x, length = %d, offset = 0x%x\n",
 				 ib_conn->page_vec->data_size, ib_conn->page_vec->length,
 				 ib_conn->page_vec->offset);
 			for (i=0 ; i<ib_conn->page_vec->length ; i++)
 				iser_err("page_vec[%d] = 0x%llx\n", i,
 					 (unsigned long long) ib_conn->page_vec->pages[i]);
 			return err;
 		}
 	}
 	return 0;
 }
	/*
	* Copyright (c) 2004, 2005, 2006 Voltaire, 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
	* 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/module.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/mm.h>
	#include <linux/highmem.h>
	#include <linux/scatterlist.h>

	#include "iscsi_iser.h"

	#define ISER_KMALLOC_THRESHOLD 0x20000 /* 128K - kmalloc limit */

	/**
	* iser_start_rdma_unaligned_sg
	*/
	static int iser_start_rdma_unaligned_sg(struct iscsi_iser_task *iser_task,
	enum iser_data_dir cmd_dir)
	{
	int dma_nents;
	struct ib_device *dev;
	char *mem = NULL;
	struct iser_data_buf *data = &iser_task->data[cmd_dir];
	unsigned long cmd_data_len = data->data_len;

	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
	mem = (void *)__get_free_pages(GFP_ATOMIC,
	ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
	else
	mem = kmalloc(cmd_data_len, GFP_ATOMIC);

	if (mem == NULL) {
	iser_err("Failed to allocate mem size %d %d for copying sglist\n",
	data->size,(int)cmd_data_len);
	return -ENOMEM;
	}

	if (cmd_dir == ISER_DIR_OUT) {
	/* copy the unaligned sg the buffer which is used for RDMA */
	struct scatterlist sgl = (struct scatterlist )data->buf;
	struct scatterlist *sg;
	int i;
	char p, from;

	p = mem;
	for_each_sg(sgl, sg, data->size, i) {
	from = kmap_atomic(sg_page(sg));
	memcpy(p,
	from + sg->offset,
	sg->length);
	kunmap_atomic(from);
	p += sg->length;
	}
	}

	sg_init_one(&iser_task->data_copy[cmd_dir].sg_single, mem, cmd_data_len);
	iser_task->data_copy[cmd_dir].buf =
	&iser_task->data_copy[cmd_dir].sg_single;
	iser_task->data_copy[cmd_dir].size = 1;

	iser_task->data_copy[cmd_dir].copy_buf = mem;

	dev = iser_task->iser_conn->ib_conn->device->ib_device;
	dma_nents = ib_dma_map_sg(dev,
	&iser_task->data_copy[cmd_dir].sg_single,
	1,
	(cmd_dir == ISER_DIR_OUT) ?
	DMA_TO_DEVICE : DMA_FROM_DEVICE);
	BUG_ON(dma_nents == 0);

	iser_task->data_copy[cmd_dir].dma_nents = dma_nents;
	return 0;
	}

	/**
	* iser_finalize_rdma_unaligned_sg
	*/
	void iser_finalize_rdma_unaligned_sg(struct iscsi_iser_task *iser_task,
	enum iser_data_dir cmd_dir)
	{
	struct ib_device *dev;
	struct iser_data_buf *mem_copy;
	unsigned long cmd_data_len;

	dev = iser_task->iser_conn->ib_conn->device->ib_device;
	mem_copy = &iser_task->data_copy[cmd_dir];

	ib_dma_unmap_sg(dev, &mem_copy->sg_single, 1,
	(cmd_dir == ISER_DIR_OUT) ?
	DMA_TO_DEVICE : DMA_FROM_DEVICE);

	if (cmd_dir == ISER_DIR_IN) {
	char *mem;
	struct scatterlist sgl, sg;
	unsigned char p, to;
	unsigned int sg_size;
	int i;

	/* copy back read RDMA to unaligned sg */
	mem = mem_copy->copy_buf;

	sgl = (struct scatterlist *)iser_task->data[ISER_DIR_IN].buf;
	sg_size = iser_task->data[ISER_DIR_IN].size;

	p = mem;
	for_each_sg(sgl, sg, sg_size, i) {
	to = kmap_atomic(sg_page(sg));
	memcpy(to + sg->offset,
	p,
	sg->length);
	kunmap_atomic(to);
	p += sg->length;
	}
	}

	cmd_data_len = iser_task->data[cmd_dir].data_len;

	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)
	free_pages((unsigned long)mem_copy->copy_buf,
	ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);
	else
	kfree(mem_copy->copy_buf);

	mem_copy->copy_buf = NULL;
	}

	#define IS_4K_ALIGNED(addr) ((((unsigned long)addr) & ~MASK_4K) == 0)

	/**
	* iser_sg_to_page_vec - Translates scatterlist entries to physical addresses
	* and returns the length of resulting physical address array (may be less than
	* the original due to possible compaction).
	*
	* we build a "page vec" under the assumption that the SG meets the RDMA
	* alignment requirements. Other then the first and last SG elements, all
	* the "internal" elements can be compacted into a list whose elements are
	* dma addresses of physical pages. The code supports also the weird case
	* where --few fragments of the same page-- are present in the SG as
	* consecutive elements. Also, it handles one entry SG.
	*/

	static int iser_sg_to_page_vec(struct iser_data_buf *data,
	struct iser_page_vec *page_vec,
	struct ib_device *ibdev)
	{
	struct scatterlist sg, sgl = (struct scatterlist *)data->buf;
	u64 start_addr, end_addr, page, chunk_start = 0;
	unsigned long total_sz = 0;
	unsigned int dma_len;
	int i, new_chunk, cur_page, last_ent = data->dma_nents - 1;

	/* compute the offset of first element */
	page_vec->offset = (u64) sgl[0].offset & ~MASK_4K;

	new_chunk = 1;
	cur_page = 0;
	for_each_sg(sgl, sg, data->dma_nents, i) {
	start_addr = ib_sg_dma_address(ibdev, sg);
	if (new_chunk)
	chunk_start = start_addr;
	dma_len = ib_sg_dma_len(ibdev, sg);
	end_addr = start_addr + dma_len;
	total_sz += dma_len;

	/* collect page fragments until aligned or end of SG list */
	if (!IS_4K_ALIGNED(end_addr) && i < last_ent) {
	new_chunk = 0;
	continue;
	}
	new_chunk = 1;

	/* address of the first page in the contiguous chunk;
	masking relevant for the very first SG entry,
	which might be unaligned */
	page = chunk_start & MASK_4K;
	do {
	page_vec->pages[cur_page++] = page;
	page += SIZE_4K;
	} while (page < end_addr);
	}

	page_vec->data_size = total_sz;
	iser_dbg("page_vec->data_size:%d cur_page %d\n", page_vec->data_size,cur_page);
	return cur_page;
	}


	/**
	* iser_data_buf_aligned_len - Tries to determine the maximal correctly aligned
	* for RDMA sub-list of a scatter-gather list of memory buffers, and returns
	* the number of entries which are aligned correctly. Supports the case where
	* consecutive SG elements are actually fragments of the same physcial page.
	*/
	static int iser_data_buf_aligned_len(struct iser_data_buf *data,
	struct ib_device *ibdev)
	{
	struct scatterlist sgl, sg, *next_sg = NULL;
	u64 start_addr, end_addr;
	int i, ret_len, start_check = 0;

	if (data->dma_nents == 1)
	return 1;

	sgl = (struct scatterlist *)data->buf;
	start_addr = ib_sg_dma_address(ibdev, sgl);

	for_each_sg(sgl, sg, data->dma_nents, i) {
	if (start_check && !IS_4K_ALIGNED(start_addr))
	break;

	next_sg = sg_next(sg);
	if (!next_sg)
	break;

	end_addr = start_addr + ib_sg_dma_len(ibdev, sg);
	start_addr = ib_sg_dma_address(ibdev, next_sg);

	if (end_addr == start_addr) {
	start_check = 0;
	continue;
	} else
	start_check = 1;

	if (!IS_4K_ALIGNED(end_addr))
	break;
	}
	ret_len = (next_sg) ? i : i+1;
	iser_dbg("Found %d aligned entries out of %d in sg:0x%p\n",
	ret_len, data->dma_nents, data);
	return ret_len;
	}

	static void iser_data_buf_dump(struct iser_data_buf *data,
	struct ib_device *ibdev)
	{
	struct scatterlist sgl = (struct scatterlist )data->buf;
	struct scatterlist *sg;
	int i;

	if (iser_debug_level == 0)
	return;

	for_each_sg(sgl, sg, data->dma_nents, i)
	iser_warn("sg[%d] dma_addr:0x%lX page:0x%p "
	"off:0x%x sz:0x%x dma_len:0x%x\n",
	i, (unsigned long)ib_sg_dma_address(ibdev, sg),
	sg_page(sg), sg->offset,
	sg->length, ib_sg_dma_len(ibdev, sg));
	}

	static void iser_dump_page_vec(struct iser_page_vec *page_vec)
	{
	int i;

	iser_err("page vec length %d data size %d\n",
	page_vec->length, page_vec->data_size);
	for (i = 0; i < page_vec->length; i++)
	iser_err("%d %lx\n",i,(unsigned long)page_vec->pages[i]);
	}

	static void iser_page_vec_build(struct iser_data_buf *data,
	struct iser_page_vec *page_vec,
	struct ib_device *ibdev)
	{
	int page_vec_len = 0;

	page_vec->length = 0;
	page_vec->offset = 0;

	iser_dbg("Translating sg sz: %d\n", data->dma_nents);
	page_vec_len = iser_sg_to_page_vec(data, page_vec, ibdev);
	iser_dbg("sg len %d page_vec_len %d\n", data->dma_nents,page_vec_len);

	page_vec->length = page_vec_len;

	if (page_vec_len * SIZE_4K < page_vec->data_size) {
	iser_err("page_vec too short to hold this SG\n");
	iser_data_buf_dump(data, ibdev);
	iser_dump_page_vec(page_vec);
	BUG();
	}
	}

	int iser_dma_map_task_data(struct iscsi_iser_task *iser_task,
	struct iser_data_buf *data,
	enum iser_data_dir iser_dir,
	enum dma_data_direction dma_dir)
	{
	struct ib_device *dev;

	iser_task->dir[iser_dir] = 1;
	dev = iser_task->iser_conn->ib_conn->device->ib_device;

	data->dma_nents = ib_dma_map_sg(dev, data->buf, data->size, dma_dir);
	if (data->dma_nents == 0) {
	iser_err("dma_map_sg failed!!!\n");
	return -EINVAL;
	}
	return 0;
	}

	void iser_dma_unmap_task_data(struct iscsi_iser_task *iser_task)
	{
	struct ib_device *dev;
	struct iser_data_buf *data;

	dev = iser_task->iser_conn->ib_conn->device->ib_device;

	if (iser_task->dir[ISER_DIR_IN]) {
	data = &iser_task->data[ISER_DIR_IN];
	ib_dma_unmap_sg(dev, data->buf, data->size, DMA_FROM_DEVICE);
	}

	if (iser_task->dir[ISER_DIR_OUT]) {
	data = &iser_task->data[ISER_DIR_OUT];
	ib_dma_unmap_sg(dev, data->buf, data->size, DMA_TO_DEVICE);
	}
	}

	/**
	* iser_reg_rdma_mem - Registers memory intended for RDMA,
	* obtaining rkey and va
	*
	* returns 0 on success, errno code on failure
	*/
	int iser_reg_rdma_mem(struct iscsi_iser_task *iser_task,
	enum iser_data_dir cmd_dir)
	{
	struct iscsi_conn *iscsi_conn = iser_task->iser_conn->iscsi_conn;
	struct iser_conn *ib_conn = iser_task->iser_conn->ib_conn;
	struct iser_device *device = ib_conn->device;
	struct ib_device *ibdev = device->ib_device;
	struct iser_data_buf *mem = &iser_task->data[cmd_dir];
	struct iser_regd_buf *regd_buf;
	int aligned_len;
	int err;
	int i;
	struct scatterlist *sg;

	regd_buf = &iser_task->rdma_regd[cmd_dir];

	aligned_len = iser_data_buf_aligned_len(mem, ibdev);
	if (aligned_len != mem->dma_nents) {
	iscsi_conn->fmr_unalign_cnt++;
	iser_warn("rdma alignment violation %d/%d aligned\n",
	aligned_len, mem->size);
	iser_data_buf_dump(mem, ibdev);

	/* unmap the command data before accessing it */
	iser_dma_unmap_task_data(iser_task);

	/* allocate copy buf, if we are writing, copy the */
	/* unaligned scatterlist, dma map the copy */
	if (iser_start_rdma_unaligned_sg(iser_task, cmd_dir) != 0)
	return -ENOMEM;
	mem = &iser_task->data_copy[cmd_dir];
	}

	/* if there a single dma entry, FMR is not needed */
	if (mem->dma_nents == 1) {
	sg = (struct scatterlist *)mem->buf;

	regd_buf->reg.lkey = device->mr->lkey;
	regd_buf->reg.rkey = device->mr->rkey;
	regd_buf->reg.len = ib_sg_dma_len(ibdev, &sg[0]);
	regd_buf->reg.va = ib_sg_dma_address(ibdev, &sg[0]);
	regd_buf->reg.is_fmr = 0;

	iser_dbg("PHYSICAL Mem.register: lkey: 0x%08X rkey: 0x%08X "
	"va: 0x%08lX sz: %ld]\n",
	(unsigned int)regd_buf->reg.lkey,
	(unsigned int)regd_buf->reg.rkey,
	(unsigned long)regd_buf->reg.va,
	(unsigned long)regd_buf->reg.len);
	} else { /* use FMR for multiple dma entries */
	iser_page_vec_build(mem, ib_conn->page_vec, ibdev);
	err = iser_reg_page_vec(ib_conn, ib_conn->page_vec, &regd_buf->reg);
	if (err) {
	iser_data_buf_dump(mem, ibdev);
	iser_err("mem->dma_nents = %d (dlength = 0x%x)\n",
	mem->dma_nents,
	ntoh24(iser_task->desc.iscsi_header.dlength));
	iser_err("page_vec: data_size = 0x%x, length = %d, offset = 0x%x\n",
	ib_conn->page_vec->data_size, ib_conn->page_vec->length,
	ib_conn->page_vec->offset);
	for (i=0 ; i<ib_conn->page_vec->length ; i++)
	iser_err("page_vec[%d] = 0x%llx\n", i,
	(unsigned long long) ib_conn->page_vec->pages[i]);
	return err;
	}
	}
	return 0;
	}