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 local_lock_t bh_lock; 44 }; 45 46 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders) = { 47 .bh_lock = INIT_LOCAL_LOCK(bh_lock), 48 }; 49 50 /** 51 * rds_page_remainder_alloc - build up regions of a message. 52 * 53 * @scat: Scatter list for message 54 * @bytes: the number of bytes needed. 55 * @gfp: the waiting behaviour of the allocation 56 * 57 * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to 58 * kmap the pages, etc. 59 * 60 * If @bytes is at least a full page then this just returns a page from 61 * alloc_page(). 62 * 63 * If @bytes is a partial page then this stores the unused region of the 64 * page in a per-cpu structure. Future partial-page allocations may be 65 * satisfied from that cached region. This lets us waste less memory on 66 * small allocations with minimal complexity. It works because the transmit 67 * path passes read-only page regions down to devices. They hold a page 68 * reference until they are done with the region. 69 */ 70 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes, 71 gfp_t gfp) 72 { 73 struct rds_page_remainder *rem; 74 struct page *page; 75 int ret; 76 77 gfp |= __GFP_HIGHMEM; 78 79 /* jump straight to allocation if we're trying for a huge page */ 80 if (bytes >= PAGE_SIZE) { 81 page = alloc_page(gfp); 82 if (!page) { 83 ret = -ENOMEM; 84 } else { 85 sg_set_page(scat, page, PAGE_SIZE, 0); 86 ret = 0; 87 } 88 goto out; 89 } 90 91 local_bh_disable(); 92 local_lock_nested_bh(&rds_page_remainders.bh_lock); 93 rem = this_cpu_ptr(&rds_page_remainders); 94 95 while (1) { 96 /* avoid a tiny region getting stuck by tossing it */ 97 if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) { 98 rds_stats_inc(s_page_remainder_miss); 99 __free_page(rem->r_page); 100 rem->r_page = NULL; 101 } 102 103 /* hand out a fragment from the cached page */ 104 if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) { 105 sg_set_page(scat, rem->r_page, bytes, rem->r_offset); 106 get_page(sg_page(scat)); 107 108 if (rem->r_offset != 0) 109 rds_stats_inc(s_page_remainder_hit); 110 111 rem->r_offset += ALIGN(bytes, 8); 112 if (rem->r_offset >= PAGE_SIZE) { 113 __free_page(rem->r_page); 114 rem->r_page = NULL; 115 } 116 ret = 0; 117 break; 118 } 119 120 /* alloc if there is nothing for us to use */ 121 local_unlock_nested_bh(&rds_page_remainders.bh_lock); 122 local_bh_enable(); 123 124 page = alloc_page(gfp); 125 126 local_bh_disable(); 127 local_lock_nested_bh(&rds_page_remainders.bh_lock); 128 rem = this_cpu_ptr(&rds_page_remainders); 129 130 if (!page) { 131 ret = -ENOMEM; 132 break; 133 } 134 135 /* did someone race to fill the remainder before us? */ 136 if (rem->r_page) { 137 __free_page(page); 138 continue; 139 } 140 141 /* otherwise install our page and loop around to alloc */ 142 rem->r_page = page; 143 rem->r_offset = 0; 144 } 145 146 local_unlock_nested_bh(&rds_page_remainders.bh_lock); 147 local_bh_enable(); 148 out: 149 rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret, 150 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset, 151 ret ? 0 : scat->length); 152 return ret; 153 } 154 EXPORT_SYMBOL_GPL(rds_page_remainder_alloc); 155 156 void rds_page_exit(void) 157 { 158 unsigned int cpu; 159 160 for_each_possible_cpu(cpu) { 161 struct rds_page_remainder *rem; 162 163 rem = &per_cpu(rds_page_remainders, cpu); 164 rdsdebug("cpu %u\n", cpu); 165 166 if (rem->r_page) 167 __free_page(rem->r_page); 168 rem->r_page = NULL; 169 } 170 } 171