release/src-rt-6.x.4708/linux/linux-2.6.36/net/rds/page.c

   1 /*
   2  * Copyright (c) 2006 Oracle.  All rights reserved.
   3  *
   4  * This software is available to you under a choice of one of two
   5  * licenses.  You may choose to be licensed under the terms of the GNU
   6  * General Public License (GPL) Version 2, available from the file
   7  * COPYING in the main directory of this source tree, or the
   8  * OpenIB.org BSD license below:
   9  *
  10  *     Redistribution and use in source and binary forms, with or
  11  *     without modification, are permitted provided that the following
  12  *     conditions are met:
  13  *
  14  *      - Redistributions of source code must retain the above
  15  *        copyright notice, this list of conditions and the following
  16  *        disclaimer.
  17  *
  18  *      - Redistributions in binary form must reproduce the above
  19  *        copyright notice, this list of conditions and the following
  20  *        disclaimer in the documentation and/or other materials
  21  *        provided with the distribution.
  22  *
  23  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30  * SOFTWARE.
  31  *
  32  */
  33 #include <linux/highmem.h>
  34 #include <linux/gfp.h>
  35
  36 #include "rds.h"
  37
  38 struct rds_page_remainder {
  39         struct page     *r_page;
  40         unsigned long   r_offset;
  41 };
  42
  43 DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders);
  44
  45 /*
  46  * returns 0 on success or -errno on failure.
  47  *
  48  * We don't have to worry about flush_dcache_page() as this only works
  49  * with private pages.  If, say, we were to do directed receive to pinned
  50  * user pages we'd have to worry more about cache coherence.  (Though
  51  * the flush_dcache_page() in get_user_pages() would probably be enough).
  52  */
  53 int rds_page_copy_user(struct page *page, unsigned long offset,
  54                        void __user *ptr, unsigned long bytes,
  55                        int to_user)
  56 {
  57         unsigned long ret;
  58         void *addr;
  59
  60         addr = kmap(page);
  61         if (to_user) {
  62                 rds_stats_add(s_copy_to_user, bytes);
  63                 ret = copy_to_user(ptr, addr + offset, bytes);
  64         } else {
  65                 rds_stats_add(s_copy_from_user, bytes);
  66                 ret = copy_from_user(addr + offset, ptr, bytes);
  67         }
  68         kunmap(page);
  69
  70         return ret ? -EFAULT : 0;
  71 }
  72 EXPORT_SYMBOL_GPL(rds_page_copy_user);
  73
  74 /*
  75  * Message allocation uses this to build up regions of a message.
  76  *
  77  * @bytes - the number of bytes needed.
  78  * @gfp - the waiting behaviour of the allocation
  79  *
  80  * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
  81  * kmap the pages, etc.
  82  *
  83  * If @bytes is at least a full page then this just returns a page from
  84  * alloc_page().
  85  *
  86  * If @bytes is a partial page then this stores the unused region of the
  87  * page in a per-cpu structure.  Future partial-page allocations may be
  88  * satisfied from that cached region.  This lets us waste less memory on
  89  * small allocations with minimal complexity.  It works because the transmit
  90  * path passes read-only page regions down to devices.  They hold a page
  91  * reference until they are done with the region.
  92  */
  93 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
  94                              gfp_t gfp)
  95 {
  96         struct rds_page_remainder *rem;
  97         unsigned long flags;
  98         struct page *page;
  99         int ret;
 100
 101         gfp |= __GFP_HIGHMEM;
 102
 103         /* jump straight to allocation if we're trying for a huge page */
 104         if (bytes >= PAGE_SIZE) {
 105                 page = alloc_page(gfp);
 106                 if (page == NULL) {
 107                         ret = -ENOMEM;
 108                 } else {
 109                         sg_set_page(scat, page, PAGE_SIZE, 0);
 110                         ret = 0;
 111                 }
 112                 goto out;
 113         }
 114
 115         rem = &per_cpu(rds_page_remainders, get_cpu());
 116         local_irq_save(flags);
 117
 118         while (1) {
 119                 /* avoid a tiny region getting stuck by tossing it */
 120                 if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
 121                         rds_stats_inc(s_page_remainder_miss);
 122                         __free_page(rem->r_page);
 123                         rem->r_page = NULL;
 124                 }
 125
 126                 /* hand out a fragment from the cached page */
 127                 if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
 128                         sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
 129                         get_page(sg_page(scat));
 130
 131                         if (rem->r_offset != 0)
 132                                 rds_stats_inc(s_page_remainder_hit);
 133
 134                         rem->r_offset += bytes;
 135                         if (rem->r_offset == PAGE_SIZE) {
 136                                 __free_page(rem->r_page);
 137                                 rem->r_page = NULL;
 138                         }
 139                         ret = 0;
 140                         break;
 141                 }
 142
 143                 /* alloc if there is nothing for us to use */
 144                 local_irq_restore(flags);
 145                 put_cpu();
 146
 147                 page = alloc_page(gfp);
 148
 149                 rem = &per_cpu(rds_page_remainders, get_cpu());
 150                 local_irq_save(flags);
 151
 152                 if (page == NULL) {
 153                         ret = -ENOMEM;
 154                         break;
 155                 }
 156
 157                 /* did someone race to fill the remainder before us? */
 158                 if (rem->r_page) {
 159                         __free_page(page);
 160                         continue;
 161                 }
 162
 163                 /* otherwise install our page and loop around to alloc */
 164                 rem->r_page = page;
 165                 rem->r_offset = 0;
 166         }
 167
 168         local_irq_restore(flags);
 169         put_cpu();
 170 out:
 171         rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
 172                  ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
 173                  ret ? 0 : scat->length);
 174         return ret;
 175 }
 176
 177 static int rds_page_remainder_cpu_notify(struct notifier_block *self,
 178                                          unsigned long action, void *hcpu)
 179 {
 180         struct rds_page_remainder *rem;
 181         long cpu = (long)hcpu;
 182
 183         rem = &per_cpu(rds_page_remainders, cpu);
 184
 185         rdsdebug("cpu %ld action 0x%lx\n", cpu, action);
 186
 187         switch (action) {
 188         case CPU_DEAD:
 189                 if (rem->r_page)
 190                         __free_page(rem->r_page);
 191                 rem->r_page = NULL;
 192                 break;
 193         }
 194
 195         return 0;
 196 }
 197
 198 static struct notifier_block rds_page_remainder_nb = {
 199         .notifier_call = rds_page_remainder_cpu_notify,
 200 };
 201
 202 void rds_page_exit(void)
 203 {
 204         int i;
 205
 206         for_each_possible_cpu(i)
 207                 rds_page_remainder_cpu_notify(&rds_page_remainder_nb,
 208                                               (unsigned long)CPU_DEAD,
 209                                               (void *)(long)i);
 210 }