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