IB/iser: iSER handling of memory for RDMA

/*

 * 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.

 *

 * $Id: iser_memory.c 6964 2006-05-07 11:11:43Z ogerlitz $

 */

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/mm.h>

#include <asm/io.h>

#include <asm/scatterlist.h>

#include <linux/scatterlist.h>

#include "iscsi_iser.h"

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

/**

 * Decrements the reference count for the

 * registered buffer & releases it

 *

 * returns 0 if released, 1 if deferred

 */

int iser_regd_buff_release(struct iser_regd_buf *regd_buf)

{

	struct device *dma_device;

	if ((atomic_read(&regd_buf->ref_count) == 0) ||

	    atomic_dec_and_test(&regd_buf->ref_count)) {

		/* if we used the dma mr, unreg is just NOP */

		if (regd_buf->reg.rkey != 0)

			iser_unreg_mem(&regd_buf->reg);

		if (regd_buf->dma_addr) {

			dma_device = regd_buf->device->ib_device->dma_device;

			dma_unmap_single(dma_device,

					 regd_buf->dma_addr,

					 regd_buf->data_size,

					 regd_buf->direction);

		}

		/* else this regd buf is associated with task which we */

		/* dma_unmap_single/sg later */

		return 0;

	} else {

		iser_dbg("Release deferred, regd.buff: 0x%p\n", regd_buf);

		return 1;

	}

}

/**

 * iser_reg_single - fills registered buffer descriptor with

 *		     registration information

 */

void iser_reg_single(struct iser_device *device,

		     struct iser_regd_buf *regd_buf,

		     enum dma_data_direction direction)

{

	dma_addr_t dma_addr;

	dma_addr  = dma_map_single(device->ib_device->dma_device,

				   regd_buf->virt_addr,

				   regd_buf->data_size, direction);

	BUG_ON(dma_mapping_error(dma_addr));

	regd_buf->reg.lkey = device->mr->lkey;

	regd_buf->reg.rkey = 0; /* indicate there's no need to unreg */

	regd_buf->reg.len  = regd_buf->data_size;

	regd_buf->reg.va   = dma_addr;

	regd_buf->dma_addr  = dma_addr;

	regd_buf->direction = direction;

}

/**

 * iser_start_rdma_unaligned_sg

 */

int iser_start_rdma_unaligned_sg(struct iscsi_iser_cmd_task  *iser_ctask,

				 enum iser_data_dir cmd_dir)

{

	int dma_nents;

	struct device *dma_device;

	char *mem = NULL;

	struct iser_data_buf *data = &iser_ctask->data[cmd_dir];

	unsigned long  cmd_data_len = data->data_len;

	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)

		mem = (void *)__get_free_pages(GFP_NOIO,

		      long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);

	else

		mem = kmalloc(cmd_data_len, GFP_NOIO);

	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 *sg = (struct scatterlist *)data->buf;

		int i;

		char *p, *from;

		for (p = mem, i = 0; i < data->size; i++) {

			from = kmap_atomic(sg[i].page, KM_USER0);

			memcpy(p,

			       from + sg[i].offset,

			       sg[i].length);

			kunmap_atomic(from, KM_USER0);

			p += sg[i].length;

		}

	}

	sg_init_one(&iser_ctask->data_copy[cmd_dir].sg_single, mem, cmd_data_len);

	iser_ctask->data_copy[cmd_dir].buf  =

		&iser_ctask->data_copy[cmd_dir].sg_single;

	iser_ctask->data_copy[cmd_dir].size = 1;

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

	dma_device = iser_ctask->iser_conn->ib_conn->device->ib_device->dma_device;

	if (cmd_dir == ISER_DIR_OUT)

		dma_nents = dma_map_sg(dma_device,

				       &iser_ctask->data_copy[cmd_dir].sg_single,

				       1, DMA_TO_DEVICE);

	else

		dma_nents = dma_map_sg(dma_device,

				       &iser_ctask->data_copy[cmd_dir].sg_single,

				       1, DMA_FROM_DEVICE);

	BUG_ON(dma_nents == 0);

	iser_ctask->data_copy[cmd_dir].dma_nents = dma_nents;

	return 0;

}

/**

 * iser_finalize_rdma_unaligned_sg

 */

void iser_finalize_rdma_unaligned_sg(struct iscsi_iser_cmd_task *iser_ctask,

				     enum iser_data_dir         cmd_dir)

{

	struct device *dma_device;

	struct iser_data_buf *mem_copy;

	unsigned long  cmd_data_len;

	dma_device = iser_ctask->iser_conn->ib_conn->device->ib_device->dma_device;

	mem_copy   = &iser_ctask->data_copy[cmd_dir];

	if (cmd_dir == ISER_DIR_OUT)

		dma_unmap_sg(dma_device, &mem_copy->sg_single, 1,

			     DMA_TO_DEVICE);

	else

		dma_unmap_sg(dma_device, &mem_copy->sg_single, 1,

			     DMA_FROM_DEVICE);

	if (cmd_dir == ISER_DIR_IN) {

		char *mem;

		struct scatterlist *sg;

		unsigned char *p, *to;

		unsigned int sg_size;

		int i;

		/* copy back read RDMA to unaligned sg */

		mem	= mem_copy->copy_buf;

		sg	= (struct scatterlist *)iser_ctask->data[ISER_DIR_IN].buf;

		sg_size = iser_ctask->data[ISER_DIR_IN].size;

		for (p = mem, i = 0; i < sg_size; i++){

			to = kmap_atomic(sg[i].page, KM_SOFTIRQ0);

			memcpy(to + sg[i].offset,

			       p,

			       sg[i].length);

			kunmap_atomic(to, KM_SOFTIRQ0);

			p += sg[i].length;

		}

	}

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

	if (cmd_data_len > ISER_KMALLOC_THRESHOLD)

		free_pages((unsigned long)mem_copy->copy_buf,

			   long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT);

	else

		kfree(mem_copy->copy_buf);

	mem_copy->copy_buf = NULL;

}

/**

 * 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 scatterlist *sg = (struct scatterlist *)data->buf;

	dma_addr_t first_addr, last_addr, page;

	int start_aligned, end_aligned;

	unsigned int cur_page = 0;

	unsigned long total_sz = 0;

	int i;

	/* compute the offset of first element */

	page_vec->offset = (u64) sg[0].offset;

	for (i = 0; i < data->dma_nents; i++) {

		total_sz += sg_dma_len(&sg[i]);

		first_addr = sg_dma_address(&sg[i]);

		last_addr  = first_addr + sg_dma_len(&sg[i]);

		start_aligned = !(first_addr & ~PAGE_MASK);

		end_aligned   = !(last_addr  & ~PAGE_MASK);

		/* continue to collect page fragments till aligned or SG ends */

		while (!end_aligned && (i + 1 < data->dma_nents)) {

			i++;

			total_sz += sg_dma_len(&sg[i]);

			last_addr = sg_dma_address(&sg[i]) + sg_dma_len(&sg[i]);

			end_aligned = !(last_addr  & ~PAGE_MASK);

		}

		first_addr = first_addr & PAGE_MASK;

		for (page = first_addr; page < last_addr; page += PAGE_SIZE)

			page_vec->pages[cur_page++] = page;

	}

	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;

}

#define MASK_4K			((1UL << 12) - 1) /* 0xFFF */

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

/**

 * 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 unsigned int iser_data_buf_aligned_len(struct iser_data_buf *data)

{

	struct scatterlist *sg;

	dma_addr_t end_addr, next_addr;

	int i, cnt;

	unsigned int ret_len = 0;

	sg = (struct scatterlist *)data->buf;

	for (cnt = 0, i = 0; i < data->dma_nents; i++, cnt++) {

		/* iser_dbg("Checking sg iobuf [%d]: phys=0x%08lX "

		   "offset: %ld sz: %ld\n", i,

		   (unsigned long)page_to_phys(sg[i].page),

		   (unsigned long)sg[i].offset,

		   (unsigned long)sg[i].length); */

		end_addr = sg_dma_address(&sg[i]) +

			   sg_dma_len(&sg[i]);

		/* iser_dbg("Checking sg iobuf end address "

		       "0x%08lX\n", end_addr); */

		if (i + 1 < data->dma_nents) {

			next_addr = sg_dma_address(&sg[i+1]);

			/* are i, i+1 fragments of the same page? */

			if (end_addr == next_addr)

				continue;

			else if (!IS_4K_ALIGNED(end_addr)) {

				ret_len = cnt + 1;

				break;

			}

		}

	}

	if (i == data->dma_nents)

		ret_len = cnt;	/* loop ended */

	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 scatterlist *sg = (struct scatterlist *)data->buf;

	int i;

	for (i = 0; i < data->size; i++)

		iser_err("sg[%d] dma_addr:0x%lX page:0x%p "

			 "off:%d sz:%d dma_len:%d\n",

			 i, (unsigned long)sg_dma_address(&sg[i]),

			 sg[i].page, sg[i].offset,

			 sg[i].length,sg_dma_len(&sg[i]));

}

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)

{

	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);

	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 * PAGE_SIZE < page_vec->data_size) {

		iser_err("page_vec too short to hold this SG\n");

		iser_data_buf_dump(data);

		iser_dump_page_vec(page_vec);

		BUG();

	}

}

/**

 * 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_cmd_task *iser_ctask,

		      enum   iser_data_dir        cmd_dir)

{

	struct iser_conn     *ib_conn = iser_ctask->iser_conn->ib_conn;

	struct iser_data_buf *mem = &iser_ctask->data[cmd_dir];

	struct iser_regd_buf *regd_buf;

	int aligned_len;

	int err;

	regd_buf = &iser_ctask->rdma_regd[cmd_dir];

	aligned_len = iser_data_buf_aligned_len(mem);

	if (aligned_len != mem->size) {

		iser_err("rdma alignment violation %d/%d aligned\n",

			 aligned_len, mem->size);

		iser_data_buf_dump(mem);

		/* allocate copy buf, if we are writing, copy the */

		/* unaligned scatterlist, dma map the copy        */

		if (iser_start_rdma_unaligned_sg(iser_ctask, cmd_dir) != 0)

				return -ENOMEM;

		mem = &iser_ctask->data_copy[cmd_dir];

	}

	iser_page_vec_build(mem, ib_conn->page_vec);

	err = iser_reg_page_vec(ib_conn, ib_conn->page_vec, &regd_buf->reg);

	if (err)

		return err;

	/* take a reference on this regd buf such that it will not be released *

	 * (eg in send dto completion) before we get the scsi response         */

	atomic_inc(&regd_buf->ref_count);

	return 0;

}