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 <linux/slab.h>
  31 #include <net/tcp.h> /* for memcpy_toiovec */
  32 #include <asm/io.h>
  33 #include <asm/uaccess.h>
  34
  35 static 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  */
  50 struct 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
 118 unpin:
 119         dma_unpin_iovec_pages(local_list);
 120 out:
 121         return NULL;
 122 }
 123
 124 void 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  */
 151 dma_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
 212 dma_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 }