drivers/dma/iovlock.c

   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 <net/tcp.h> /* for memcpy_toiovec */
  31 #include <asm/io.h>
  32 #include <asm/uaccess.h>
  33
  34 static int num_pages_spanned(struct iovec *iov)
  35 {
  36         return
  37         ((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
  38         ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
  39 }
  40
  41 /*
  42  * Pin down all the iovec pages needed for len bytes.
  43  * Return a struct dma_pinned_list to keep track of pages pinned down.
  44  *
  45  * We are allocating a single chunk of memory, and then carving it up into
  46  * 3 sections, the latter 2 whose size depends on the number of iovecs and the
  47  * total number of pages, respectively.
  48  */
  49 struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
  50 {
  51         struct dma_pinned_list *local_list;
  52         struct page **pages;
  53         int i;
  54         int ret;
  55         int nr_iovecs = 0;
  56         int iovec_len_used = 0;
  57         int iovec_pages_used = 0;
  58
  59         /* don't pin down non-user-based iovecs */
  60         if (segment_eq(get_fs(), KERNEL_DS))
  61                 return NULL;
  62
  63         /* determine how many iovecs/pages there are, up front */
  64         do {
  65                 iovec_len_used += iov[nr_iovecs].iov_len;
  66                 iovec_pages_used += num_pages_spanned(&iov[nr_iovecs]);
  67                 nr_iovecs++;
  68         } while (iovec_len_used < len);
  69
  70         /* single kmalloc for pinned list, page_list[], and the page arrays */
  71         local_list = kmalloc(sizeof(*local_list)
  72                 + (nr_iovecs * sizeof (struct dma_page_list))
  73                 + (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
  74         if (!local_list)
  75                 goto out;
  76
  77         /* list of pages starts right after the page list array */
  78         pages = (struct page **) &local_list->page_list[nr_iovecs];
  79
  80         local_list->nr_iovecs = 0;
  81
  82         for (i = 0; i < nr_iovecs; i++) {
  83                 struct dma_page_list *page_list = &local_list->page_list[i];
  84
  85                 len -= iov[i].iov_len;
  86
  87                 if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len))
  88                         goto unpin;
  89
  90                 page_list->nr_pages = num_pages_spanned(&iov[i]);
  91                 page_list->base_address = iov[i].iov_base;
  92
  93                 page_list->pages = pages;
  94                 pages += page_list->nr_pages;
  95
  96                 /* pin pages down */
  97                 down_read(&current->mm->mmap_sem);
  98                 ret = get_user_pages(
  99                         current,
 100                         current->mm,
 101                         (unsigned long) iov[i].iov_base,
 102                         page_list->nr_pages,
 103                         1,      /* write */
 104                         0,      /* force */
 105                         page_list->pages,
 106                         NULL);
 107                 up_read(&current->mm->mmap_sem);
 108
 109                 if (ret != page_list->nr_pages)
 110                         goto unpin;
 111
 112                 local_list->nr_iovecs = i + 1;
 113         }
 114
 115         return local_list;
 116
 117 unpin:
 118         dma_unpin_iovec_pages(local_list);
 119 out:
 120         return NULL;
 121 }
 122
 123 void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
 124 {
 125         int i, j;
 126
 127         if (!pinned_list)
 128                 return;
 129
 130         for (i = 0; i < pinned_list->nr_iovecs; i++) {
 131                 struct dma_page_list *page_list = &pinned_list->page_list[i];
 132                 for (j = 0; j < page_list->nr_pages; j++) {
 133                         set_page_dirty_lock(page_list->pages[j]);
 134                         page_cache_release(page_list->pages[j]);
 135                 }
 136         }
 137
 138         kfree(pinned_list);
 139 }
 140
 141
 142 /*
 143  * We have already pinned down the pages we will be using in the iovecs.
 144  * Each entry in iov array has corresponding entry in pinned_list->page_list.
 145  * Using array indexing to keep iov[] and page_list[] in sync.
 146  * Initial elements in iov array's iov->iov_len will be 0 if already copied into
 147  *   by another call.
 148  * iov array length remaining guaranteed to be bigger than len.
 149  */
 150 dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
 151         struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len)
 152 {
 153         int iov_byte_offset;
 154         int copy;
 155         dma_cookie_t dma_cookie = 0;
 156         int iovec_idx;
 157         int page_idx;
 158
 159         if (!chan)
 160                 return memcpy_toiovec(iov, kdata, len);
 161
 162         iovec_idx = 0;
 163         while (iovec_idx < pinned_list->nr_iovecs) {
 164                 struct dma_page_list *page_list;
 165
 166                 /* skip already used-up iovecs */
 167                 while (!iov[iovec_idx].iov_len)
 168                         iovec_idx++;
 169
 170                 page_list = &pinned_list->page_list[iovec_idx];
 171
 172                 iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
 173                 page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
 174                          - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
 175
 176                 /* break up copies to not cross page boundary */
 177                 while (iov[iovec_idx].iov_len) {
 178                         copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
 179                         copy = min_t(int, copy, iov[iovec_idx].iov_len);
 180
 181                         dma_cookie = dma_async_memcpy_buf_to_pg(chan,
 182                                         page_list->pages[page_idx],
 183                                         iov_byte_offset,
 184                                         kdata,
 185                                         copy);
 186
 187                         len -= copy;
 188                         iov[iovec_idx].iov_len -= copy;
 189                         iov[iovec_idx].iov_base += copy;
 190
 191                         if (!len)
 192                                 return dma_cookie;
 193
 194                         kdata += copy;
 195                         iov_byte_offset = 0;
 196                         page_idx++;
 197                 }
 198                 iovec_idx++;
 199         }
 200
 201         /* really bad if we ever run out of iovecs */
 202         BUG();
 203         return -EFAULT;
 204 }
 205
 206 dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
 207         struct dma_pinned_list *pinned_list, struct page *page,
 208         unsigned int offset, size_t len)
 209 {
 210         int iov_byte_offset;
 211         int copy;
 212         dma_cookie_t dma_cookie = 0;
 213         int iovec_idx;
 214         int page_idx;
 215         int err;
 216
 217         /* this needs as-yet-unimplemented buf-to-buff, so punt. */
 218         /* TODO: use dma for this */
 219         if (!chan || !pinned_list) {
 220                 u8 *vaddr = kmap(page);
 221                 err = memcpy_toiovec(iov, vaddr + offset, len);
 222                 kunmap(page);
 223                 return err;
 224         }
 225
 226         iovec_idx = 0;
 227         while (iovec_idx < pinned_list->nr_iovecs) {
 228                 struct dma_page_list *page_list;
 229
 230                 /* skip already used-up iovecs */
 231                 while (!iov[iovec_idx].iov_len)
 232                         iovec_idx++;
 233
 234                 page_list = &pinned_list->page_list[iovec_idx];
 235
 236                 iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
 237                 page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
 238                          - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
 239
 240                 /* break up copies to not cross page boundary */
 241                 while (iov[iovec_idx].iov_len) {
 242                         copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
 243                         copy = min_t(int, copy, iov[iovec_idx].iov_len);
 244
 245                         dma_cookie = dma_async_memcpy_pg_to_pg(chan,
 246                                         page_list->pages[page_idx],
 247                                         iov_byte_offset,
 248                                         page,
 249                                         offset,
 250                                         copy);
 251
 252                         len -= copy;
 253                         iov[iovec_idx].iov_len -= copy;
 254                         iov[iovec_idx].iov_base += copy;
 255
 256                         if (!len)
 257                                 return dma_cookie;
 258
 259                         offset += copy;
 260                         iov_byte_offset = 0;
 261                         page_idx++;
 262                 }
 263                 iovec_idx++;
 264         }
 265
 266         /* really bad if we ever run out of iovecs */
 267         BUG();
 268         return -EFAULT;
 269 }