iovlock.c

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/*
 * 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;
}