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 #include <linux/cpu.h> 36 #include <linux/export.h> 37 38 #include "rds.h" 39 40 struct rds_page_remainder { 41 struct page *r_page; 42 unsigned long r_offset; 43 }; 44 45 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, 46 rds_page_remainders); 47 48 /* 49 * returns 0 on success or -errno on failure. 50 * 51 * We don't have to worry about flush_dcache_page() as this only works 52 * with private pages. If, say, we were to do directed receive to pinned 53 * user pages we'd have to worry more about cache coherence. (Though 54 * the flush_dcache_page() in get_user_pages() would probably be enough). 55 */ 56 int rds_page_copy_user(struct page *page, unsigned long offset, 57 void __user *ptr, unsigned long bytes, 58 int to_user) 59 { 60 unsigned long ret; 61 void *addr; 62 63 addr = kmap(page); 64 if (to_user) { 65 rds_stats_add(s_copy_to_user, bytes); 66 ret = copy_to_user(ptr, addr + offset, bytes); 67 } else { 68 rds_stats_add(s_copy_from_user, bytes); 69 ret = copy_from_user(addr + offset, ptr, bytes); 70 } 71 kunmap(page); 72 73 return ret ? -EFAULT : 0; 74 } 75 EXPORT_SYMBOL_GPL(rds_page_copy_user); 76 77 /** 78 * rds_page_remainder_alloc - build up regions of a message. 79 * 80 * @scat: Scatter list for message 81 * @bytes: the number of bytes needed. 82 * @gfp: the waiting behaviour of the allocation 83 * 84 * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to 85 * kmap the pages, etc. 86 * 87 * If @bytes is at least a full page then this just returns a page from 88 * alloc_page(). 89 * 90 * If @bytes is a partial page then this stores the unused region of the 91 * page in a per-cpu structure. Future partial-page allocations may be 92 * satisfied from that cached region. This lets us waste less memory on 93 * small allocations with minimal complexity. It works because the transmit 94 * path passes read-only page regions down to devices. They hold a page 95 * reference until they are done with the region. 96 */ 97 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes, 98 gfp_t gfp) 99 { 100 struct rds_page_remainder *rem; 101 unsigned long flags; 102 struct page *page; 103 int ret; 104 105 gfp |= __GFP_HIGHMEM; 106 107 /* jump straight to allocation if we're trying for a huge page */ 108 if (bytes >= PAGE_SIZE) { 109 page = alloc_page(gfp); 110 if (!page) { 111 ret = -ENOMEM; 112 } else { 113 sg_set_page(scat, page, PAGE_SIZE, 0); 114 ret = 0; 115 } 116 goto out; 117 } 118 119 rem = &per_cpu(rds_page_remainders, get_cpu()); 120 local_irq_save(flags); 121 122 while (1) { 123 /* avoid a tiny region getting stuck by tossing it */ 124 if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) { 125 rds_stats_inc(s_page_remainder_miss); 126 __free_page(rem->r_page); 127 rem->r_page = NULL; 128 } 129 130 /* hand out a fragment from the cached page */ 131 if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) { 132 sg_set_page(scat, rem->r_page, bytes, rem->r_offset); 133 get_page(sg_page(scat)); 134 135 if (rem->r_offset != 0) 136 rds_stats_inc(s_page_remainder_hit); 137 138 rem->r_offset += bytes; 139 if (rem->r_offset == PAGE_SIZE) { 140 __free_page(rem->r_page); 141 rem->r_page = NULL; 142 } 143 ret = 0; 144 break; 145 } 146 147 /* alloc if there is nothing for us to use */ 148 local_irq_restore(flags); 149 put_cpu(); 150 151 page = alloc_page(gfp); 152 153 rem = &per_cpu(rds_page_remainders, get_cpu()); 154 local_irq_save(flags); 155 156 if (!page) { 157 ret = -ENOMEM; 158 break; 159 } 160 161 /* did someone race to fill the remainder before us? */ 162 if (rem->r_page) { 163 __free_page(page); 164 continue; 165 } 166 167 /* otherwise install our page and loop around to alloc */ 168 rem->r_page = page; 169 rem->r_offset = 0; 170 } 171 172 local_irq_restore(flags); 173 put_cpu(); 174 out: 175 rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret, 176 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset, 177 ret ? 0 : scat->length); 178 return ret; 179 } 180 EXPORT_SYMBOL_GPL(rds_page_remainder_alloc); 181 182 void rds_page_exit(void) 183 { 184 unsigned int cpu; 185 186 for_each_possible_cpu(cpu) { 187 struct rds_page_remainder *rem; 188 189 rem = &per_cpu(rds_page_remainders, cpu); 190 rdsdebug("cpu %u\n", cpu); 191 192 if (rem->r_page) 193 __free_page(rem->r_page); 194 rem->r_page = NULL; 195 } 196 } 197