iovlock.c

/*
 * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
 * Portions based on net/core/datagram.c and copyrighted by their authors.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * The full GNU General Public License is included in this distribution in the
 * file called COPYING.
 */

/*
 * This code allows the net stack to make use of a DMA engine for
 * skb to iovec copies.
 */

#include <linux/dmaengine.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <net/tcp.h> /* for memcpy_toiovec */
#include <asm/io.h>
#include <asm/uaccess.h>

static int num_pages_spanned(struct iovec *iov)
{
	return
	((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
	((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
}

/*
 * Pin down all the iovec pages needed for len bytes.
 * Return a struct dma_pinned_list to keep track of pages pinned down.
 *
 * We are allocating a single chunk of memory, and then carving it up into
 * 3 sections, the latter 2 whose size depends on the number of iovecs and the
 * total number of pages, respectively.
 */
struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
{
	struct dma_pinned_list *local_list;
	struct page **pages;
	int i;
	int ret;
	int nr_iovecs = 0;
	int iovec_len_used = 0;
	int iovec_pages_used = 0;

	/* don't pin down non-user-based iovecs */
	if (segment_eq(get_fs(), KERNEL_DS))
		return NULL;

	/* determine how many iovecs/pages there are, up front */
	do {
		iovec_len_used += iov[nr_iovecs].iov_len;
		iovec_pages_used += num_pages_spanned(&iov[nr_iovecs]);
		nr_iovecs++;
	} while (iovec_len_used < len);

	/* single kmalloc for pinned list, page_list[], and the page arrays */
	local_list = kmalloc(sizeof(*local_list)
		+ (nr_iovecs * sizeof (struct dma_page_list))
		+ (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
	if (!local_list)
		goto out;

	/* list of pages starts right after the page list array */
	pages = (struct page **) &local_list->page_list[nr_iovecs];

	local_list->nr_iovecs = 0;

	for (i = 0; i < nr_iovecs; i++) {
		struct dma_page_list *page_list = &local_list->page_list[i];

		len -= iov[i].iov_len;

		if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len))
			goto unpin;

		page_list->nr_pages = num_pages_spanned(&iov[i]);
		page_list->base_address = iov[i].iov_base;

		page_list->pages = pages;
		pages += page_list->nr_pages;

		/* pin pages down */
		down_read(&current->mm->mmap_sem);
		ret = get_user_pages(
			current,
			current->mm,
			(unsigned long) iov[i].iov_base,
			page_list->nr_pages,
			1,	/* write */
			0,	/* force */
			page_list->pages,
			NULL);
		up_read(&current->mm->mmap_sem);

		if (ret != page_list->nr_pages)
			goto unpin;

		local_list->nr_iovecs = i + 1;
	}

	return local_list;

unpin:
	dma_unpin_iovec_pages(local_list);
out:
	return NULL;
}

void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
{
	int i, j;

	if (!pinned_list)
		return;

	for (i = 0; i < pinned_list->nr_iovecs; i++) {
		struct dma_page_list *page_list = &pinned_list->page_list[i];
		for (j = 0; j < page_list->nr_pages; j++) {
			set_page_dirty_lock(page_list->pages[j]);
			page_cache_release(page_list->pages[j]);
		}
	}

	kfree(pinned_list);
}


/*
 * We have already pinned down the pages we will be using in the iovecs.
 * Each entry in iov array has corresponding entry in pinned_list->page_list.
 * Using array indexing to keep iov[] and page_list[] in sync.
 * Initial elements in iov array's iov->iov_len will be 0 if already copied into
 *   by another call.
 * iov array length remaining guaranteed to be bigger than len.
 */
dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
	struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len)
{
	int iov_byte_offset;
	int copy;
	dma_cookie_t dma_cookie = 0;
	int iovec_idx;
	int page_idx;

	if (!chan)
		return memcpy_toiovec(iov, kdata, len);

	iovec_idx = 0;
	while (iovec_idx < pinned_list->nr_iovecs) {
		struct dma_page_list *page_list;

		/* skip already used-up iovecs */
		while (!iov[iovec_idx].iov_len)
			iovec_idx++;

		page_list = &pinned_list->page_list[iovec_idx];

		iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
		page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
			 - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;

		/* break up copies to not cross page boundary */
		while (iov[iovec_idx].iov_len) {
			copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
			copy = min_t(int, copy, iov[iovec_idx].iov_len);

			dma_cookie = dma_async_memcpy_buf_to_pg(chan,
					page_list->pages[page_idx],
					iov_byte_offset,
					kdata,
					copy);
			/* poll for a descriptor slot */
			if (unlikely(dma_cookie < 0)) {
				dma_async_issue_pending(chan);
				continue;
			}

			len -= copy;
			iov[iovec_idx].iov_len -= copy;
			iov[iovec_idx].iov_base += copy;

			if (!len)
				return dma_cookie;

			kdata += copy;
			iov_byte_offset = 0;
			page_idx++;
		}
		iovec_idx++;
	}

	/* really bad if we ever run out of iovecs */
	BUG();
	return -EFAULT;
}

dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
	struct dma_pinned_list *pinned_list, struct page *page,
	unsigned int offset, size_t len)
{
	int iov_byte_offset;
	int copy;
	dma_cookie_t dma_cookie = 0;
	int iovec_idx;
	int page_idx;
	int err;

	/* this needs as-yet-unimplemented buf-to-buff, so punt. */
	/* TODO: use dma for this */
	if (!chan || !pinned_list) {
		u8 *vaddr = kmap(page);
		err = memcpy_toiovec(iov, vaddr + offset, len);
		kunmap(page);
		return err;
	}

	iovec_idx = 0;
	while (iovec_idx < pinned_list->nr_iovecs) {
		struct dma_page_list *page_list;

		/* skip already used-up iovecs */
		while (!iov[iovec_idx].iov_len)
			iovec_idx++;

		page_list = &pinned_list->page_list[iovec_idx];

		iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
		page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
			 - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;

		/* break up copies to not cross page boundary */
		while (iov[iovec_idx].iov_len) {
			copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
			copy = min_t(int, copy, iov[iovec_idx].iov_len);

			dma_cookie = dma_async_memcpy_pg_to_pg(chan,
					page_list->pages[page_idx],
					iov_byte_offset,
					page,
					offset,
					copy);
			/* poll for a descriptor slot */
			if (unlikely(dma_cookie < 0)) {
				dma_async_issue_pending(chan);
				continue;
			}

			len -= copy;
			iov[iovec_idx].iov_len -= copy;
			iov[iovec_idx].iov_base += copy;

			if (!len)
				return dma_cookie;

			offset += copy;
			iov_byte_offset = 0;
			page_idx++;
		}
		iovec_idx++;
	}

	/* really bad if we ever run out of iovecs */
	BUG();
	return -EFAULT;
}