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 */
rds_page_remainder_alloc(struct scatterlist * scat,unsigned long bytes,gfp_t gfp)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
rds_page_exit(void)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