linux/drivers/dma/iovlock.c
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   1/*
   2 * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
   3 * Portions based on net/core/datagram.c and copyrighted by their authors.
   4 *
   5 * This program is free software; you can redistribute it and/or modify it
   6 * under the terms of the GNU General Public License as published by the Free
   7 * Software Foundation; either version 2 of the License, or (at your option)
   8 * any later version.
   9 *
  10 * This program is distributed in the hope that it will be useful, but WITHOUT
  11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13 * more details.
  14 *
  15 * You should have received a copy of the GNU General Public License along with
  16 * this program; if not, write to the Free Software Foundation, Inc., 59
  17 * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18 *
  19 * The full GNU General Public License is included in this distribution in the
  20 * file called COPYING.
  21 */
  22
  23/*
  24 * This code allows the net stack to make use of a DMA engine for
  25 * skb to iovec copies.
  26 */
  27
  28#include <linux/dmaengine.h>
  29#include <linux/pagemap.h>
  30#include <linux/slab.h>
  31#include <net/tcp.h> /* for memcpy_toiovec */
  32#include <asm/io.h>
  33#include <asm/uaccess.h>
  34
  35static int num_pages_spanned(struct iovec *iov)
  36{
  37        return
  38        ((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
  39        ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
  40}
  41
  42/*
  43 * Pin down all the iovec pages needed for len bytes.
  44 * Return a struct dma_pinned_list to keep track of pages pinned down.
  45 *
  46 * We are allocating a single chunk of memory, and then carving it up into
  47 * 3 sections, the latter 2 whose size depends on the number of iovecs and the
  48 * total number of pages, respectively.
  49 */
  50struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
  51{
  52        struct dma_pinned_list *local_list;
  53        struct page **pages;
  54        int i;
  55        int ret;
  56        int nr_iovecs = 0;
  57        int iovec_len_used = 0;
  58        int iovec_pages_used = 0;
  59
  60        /* don't pin down non-user-based iovecs */
  61        if (segment_eq(get_fs(), KERNEL_DS))
  62                return NULL;
  63
  64        /* determine how many iovecs/pages there are, up front */
  65        do {
  66                iovec_len_used += iov[nr_iovecs].iov_len;
  67                iovec_pages_used += num_pages_spanned(&iov[nr_iovecs]);
  68                nr_iovecs++;
  69        } while (iovec_len_used < len);
  70
  71        /* single kmalloc for pinned list, page_list[], and the page arrays */
  72        local_list = kmalloc(sizeof(*local_list)
  73                + (nr_iovecs * sizeof (struct dma_page_list))
  74                + (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
  75        if (!local_list)
  76                goto out;
  77
  78        /* list of pages starts right after the page list array */
  79        pages = (struct page **) &local_list->page_list[nr_iovecs];
  80
  81        local_list->nr_iovecs = 0;
  82
  83        for (i = 0; i < nr_iovecs; i++) {
  84                struct dma_page_list *page_list = &local_list->page_list[i];
  85
  86                len -= iov[i].iov_len;
  87
  88                if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len))
  89                        goto unpin;
  90
  91                page_list->nr_pages = num_pages_spanned(&iov[i]);
  92                page_list->base_address = iov[i].iov_base;
  93
  94                page_list->pages = pages;
  95                pages += page_list->nr_pages;
  96
  97                /* pin pages down */
  98                down_read(&current->mm->mmap_sem);
  99                ret = get_user_pages(
 100                        current,
 101                        current->mm,
 102                        (unsigned long) iov[i].iov_base,
 103                        page_list->nr_pages,
 104                        1,      /* write */
 105                        0,      /* force */
 106                        page_list->pages,
 107                        NULL);
 108                up_read(&current->mm->mmap_sem);
 109
 110                if (ret != page_list->nr_pages)
 111                        goto unpin;
 112
 113                local_list->nr_iovecs = i + 1;
 114        }
 115
 116        return local_list;
 117
 118unpin:
 119        dma_unpin_iovec_pages(local_list);
 120out:
 121        return NULL;
 122}
 123
 124void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
 125{
 126        int i, j;
 127
 128        if (!pinned_list)
 129                return;
 130
 131        for (i = 0; i < pinned_list->nr_iovecs; i++) {
 132                struct dma_page_list *page_list = &pinned_list->page_list[i];
 133                for (j = 0; j < page_list->nr_pages; j++) {
 134                        set_page_dirty_lock(page_list->pages[j]);
 135                        page_cache_release(page_list->pages[j]);
 136                }
 137        }
 138
 139        kfree(pinned_list);
 140}
 141
 142
 143/*
 144 * We have already pinned down the pages we will be using in the iovecs.
 145 * Each entry in iov array has corresponding entry in pinned_list->page_list.
 146 * Using array indexing to keep iov[] and page_list[] in sync.
 147 * Initial elements in iov array's iov->iov_len will be 0 if already copied into
 148 *   by another call.
 149 * iov array length remaining guaranteed to be bigger than len.
 150 */
 151dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
 152        struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len)
 153{
 154        int iov_byte_offset;
 155        int copy;
 156        dma_cookie_t dma_cookie = 0;
 157        int iovec_idx;
 158        int page_idx;
 159
 160        if (!chan)
 161                return memcpy_toiovec(iov, kdata, len);
 162
 163        iovec_idx = 0;
 164        while (iovec_idx < pinned_list->nr_iovecs) {
 165                struct dma_page_list *page_list;
 166
 167                /* skip already used-up iovecs */
 168                while (!iov[iovec_idx].iov_len)
 169                        iovec_idx++;
 170
 171                page_list = &pinned_list->page_list[iovec_idx];
 172
 173                iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
 174                page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
 175                         - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
 176
 177                /* break up copies to not cross page boundary */
 178                while (iov[iovec_idx].iov_len) {
 179                        copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
 180                        copy = min_t(int, copy, iov[iovec_idx].iov_len);
 181
 182                        dma_cookie = dma_async_memcpy_buf_to_pg(chan,
 183                                        page_list->pages[page_idx],
 184                                        iov_byte_offset,
 185                                        kdata,
 186                                        copy);
 187                        /* poll for a descriptor slot */
 188                        if (unlikely(dma_cookie < 0)) {
 189                                dma_async_issue_pending(chan);
 190                                continue;
 191                        }
 192
 193                        len -= copy;
 194                        iov[iovec_idx].iov_len -= copy;
 195                        iov[iovec_idx].iov_base += copy;
 196
 197                        if (!len)
 198                                return dma_cookie;
 199
 200                        kdata += copy;
 201                        iov_byte_offset = 0;
 202                        page_idx++;
 203                }
 204                iovec_idx++;
 205        }
 206
 207        /* really bad if we ever run out of iovecs */
 208        BUG();
 209        return -EFAULT;
 210}
 211
 212dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
 213        struct dma_pinned_list *pinned_list, struct page *page,
 214        unsigned int offset, size_t len)
 215{
 216        int iov_byte_offset;
 217        int copy;
 218        dma_cookie_t dma_cookie = 0;
 219        int iovec_idx;
 220        int page_idx;
 221        int err;
 222
 223        /* this needs as-yet-unimplemented buf-to-buff, so punt. */
 224        /* TODO: use dma for this */
 225        if (!chan || !pinned_list) {
 226                u8 *vaddr = kmap(page);
 227                err = memcpy_toiovec(iov, vaddr + offset, len);
 228                kunmap(page);
 229                return err;
 230        }
 231
 232        iovec_idx = 0;
 233        while (iovec_idx < pinned_list->nr_iovecs) {
 234                struct dma_page_list *page_list;
 235
 236                /* skip already used-up iovecs */
 237                while (!iov[iovec_idx].iov_len)
 238                        iovec_idx++;
 239
 240                page_list = &pinned_list->page_list[iovec_idx];
 241
 242                iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
 243                page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
 244                         - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
 245
 246                /* break up copies to not cross page boundary */
 247                while (iov[iovec_idx].iov_len) {
 248                        copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
 249                        copy = min_t(int, copy, iov[iovec_idx].iov_len);
 250
 251                        dma_cookie = dma_async_memcpy_pg_to_pg(chan,
 252                                        page_list->pages[page_idx],
 253                                        iov_byte_offset,
 254                                        page,
 255                                        offset,
 256                                        copy);
 257                        /* poll for a descriptor slot */
 258                        if (unlikely(dma_cookie < 0)) {
 259                                dma_async_issue_pending(chan);
 260                                continue;
 261                        }
 262
 263                        len -= copy;
 264                        iov[iovec_idx].iov_len -= copy;
 265                        iov[iovec_idx].iov_base += copy;
 266
 267                        if (!len)
 268                                return dma_cookie;
 269
 270                        offset += copy;
 271                        iov_byte_offset = 0;
 272                        page_idx++;
 273                }
 274                iovec_idx++;
 275        }
 276
 277        /* really bad if we ever run out of iovecs */
 278        BUG();
 279        return -EFAULT;
 280}
 281
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