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 */
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
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 }