xref: /openbmc/linux/net/rds/page.c (revision 82ced6fd)
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 
35 #include "rds.h"
36 
37 struct rds_page_remainder {
38 	struct page	*r_page;
39 	unsigned long	r_offset;
40 };
41 
42 DEFINE_PER_CPU(struct rds_page_remainder, rds_page_remainders) ____cacheline_aligned;
43 
44 /*
45  * returns 0 on success or -errno on failure.
46  *
47  * We don't have to worry about flush_dcache_page() as this only works
48  * with private pages.  If, say, we were to do directed receive to pinned
49  * user pages we'd have to worry more about cache coherence.  (Though
50  * the flush_dcache_page() in get_user_pages() would probably be enough).
51  */
52 int rds_page_copy_user(struct page *page, unsigned long offset,
53 		       void __user *ptr, unsigned long bytes,
54 		       int to_user)
55 {
56 	unsigned long ret;
57 	void *addr;
58 
59 	if (to_user)
60 		rds_stats_add(s_copy_to_user, bytes);
61 	else
62 		rds_stats_add(s_copy_from_user, bytes);
63 
64 	addr = kmap_atomic(page, KM_USER0);
65 	if (to_user)
66 		ret = __copy_to_user_inatomic(ptr, addr + offset, bytes);
67 	else
68 		ret = __copy_from_user_inatomic(addr + offset, ptr, bytes);
69 	kunmap_atomic(addr, KM_USER0);
70 
71 	if (ret) {
72 		addr = kmap(page);
73 		if (to_user)
74 			ret = copy_to_user(ptr, addr + offset, bytes);
75 		else
76 			ret = copy_from_user(addr + offset, ptr, bytes);
77 		kunmap(page);
78 		if (ret)
79 			return -EFAULT;
80 	}
81 
82 	return 0;
83 }
84 
85 /*
86  * Message allocation uses this to build up regions of a message.
87  *
88  * @bytes - the number of bytes needed.
89  * @gfp - the waiting behaviour of the allocation
90  *
91  * @gfp is always ored with __GFP_HIGHMEM.  Callers must be prepared to
92  * kmap the pages, etc.
93  *
94  * If @bytes is at least a full page then this just returns a page from
95  * alloc_page().
96  *
97  * If @bytes is a partial page then this stores the unused region of the
98  * page in a per-cpu structure.  Future partial-page allocations may be
99  * satisfied from that cached region.  This lets us waste less memory on
100  * small allocations with minimal complexity.  It works because the transmit
101  * path passes read-only page regions down to devices.  They hold a page
102  * reference until they are done with the region.
103  */
104 int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
105 			     gfp_t gfp)
106 {
107 	struct rds_page_remainder *rem;
108 	unsigned long flags;
109 	struct page *page;
110 	int ret;
111 
112 	gfp |= __GFP_HIGHMEM;
113 
114 	/* jump straight to allocation if we're trying for a huge page */
115 	if (bytes >= PAGE_SIZE) {
116 		page = alloc_page(gfp);
117 		if (page == NULL) {
118 			ret = -ENOMEM;
119 		} else {
120 			sg_set_page(scat, page, PAGE_SIZE, 0);
121 			ret = 0;
122 		}
123 		goto out;
124 	}
125 
126 	rem = &per_cpu(rds_page_remainders, get_cpu());
127 	local_irq_save(flags);
128 
129 	while (1) {
130 		/* avoid a tiny region getting stuck by tossing it */
131 		if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
132 			rds_stats_inc(s_page_remainder_miss);
133 			__free_page(rem->r_page);
134 			rem->r_page = NULL;
135 		}
136 
137 		/* hand out a fragment from the cached page */
138 		if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
139 			sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
140 			get_page(sg_page(scat));
141 
142 			if (rem->r_offset != 0)
143 				rds_stats_inc(s_page_remainder_hit);
144 
145 			rem->r_offset += bytes;
146 			if (rem->r_offset == PAGE_SIZE) {
147 				__free_page(rem->r_page);
148 				rem->r_page = NULL;
149 			}
150 			ret = 0;
151 			break;
152 		}
153 
154 		/* alloc if there is nothing for us to use */
155 		local_irq_restore(flags);
156 		put_cpu();
157 
158 		page = alloc_page(gfp);
159 
160 		rem = &per_cpu(rds_page_remainders, get_cpu());
161 		local_irq_save(flags);
162 
163 		if (page == NULL) {
164 			ret = -ENOMEM;
165 			break;
166 		}
167 
168 		/* did someone race to fill the remainder before us? */
169 		if (rem->r_page) {
170 			__free_page(page);
171 			continue;
172 		}
173 
174 		/* otherwise install our page and loop around to alloc */
175 		rem->r_page = page;
176 		rem->r_offset = 0;
177 	}
178 
179 	local_irq_restore(flags);
180 	put_cpu();
181 out:
182 	rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
183 		 ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
184 		 ret ? 0 : scat->length);
185 	return ret;
186 }
187 
188 static int rds_page_remainder_cpu_notify(struct notifier_block *self,
189 					 unsigned long action, void *hcpu)
190 {
191 	struct rds_page_remainder *rem;
192 	long cpu = (long)hcpu;
193 
194 	rem = &per_cpu(rds_page_remainders, cpu);
195 
196 	rdsdebug("cpu %ld action 0x%lx\n", cpu, action);
197 
198 	switch (action) {
199 	case CPU_DEAD:
200 		if (rem->r_page)
201 			__free_page(rem->r_page);
202 		rem->r_page = NULL;
203 		break;
204 	}
205 
206 	return 0;
207 }
208 
209 static struct notifier_block rds_page_remainder_nb = {
210 	.notifier_call = rds_page_remainder_cpu_notify,
211 };
212 
213 void rds_page_exit(void)
214 {
215 	int i;
216 
217 	for_each_possible_cpu(i)
218 		rds_page_remainder_cpu_notify(&rds_page_remainder_nb,
219 					      (unsigned long)CPU_DEAD,
220 					      (void *)(long)i);
221 }
222