Root/net/rds/page.c

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
36#include "rds.h"
37
38struct rds_page_remainder {
39    struct page *r_page;
40    unsigned long r_offset;
41};
42
43DEFINE_PER_CPU_SHARED_ALIGNED(struct rds_page_remainder, rds_page_remainders);
44
45/*
46 * returns 0 on success or -errno on failure.
47 *
48 * We don't have to worry about flush_dcache_page() as this only works
49 * with private pages. If, say, we were to do directed receive to pinned
50 * user pages we'd have to worry more about cache coherence. (Though
51 * the flush_dcache_page() in get_user_pages() would probably be enough).
52 */
53int rds_page_copy_user(struct page *page, unsigned long offset,
54               void __user *ptr, unsigned long bytes,
55               int to_user)
56{
57    unsigned long ret;
58    void *addr;
59
60    if (to_user)
61        rds_stats_add(s_copy_to_user, bytes);
62    else
63        rds_stats_add(s_copy_from_user, bytes);
64
65    addr = kmap_atomic(page, KM_USER0);
66    if (to_user)
67        ret = __copy_to_user_inatomic(ptr, addr + offset, bytes);
68    else
69        ret = __copy_from_user_inatomic(addr + offset, ptr, bytes);
70    kunmap_atomic(addr, KM_USER0);
71
72    if (ret) {
73        addr = kmap(page);
74        if (to_user)
75            ret = copy_to_user(ptr, addr + offset, bytes);
76        else
77            ret = copy_from_user(addr + offset, ptr, bytes);
78        kunmap(page);
79        if (ret)
80            return -EFAULT;
81    }
82
83    return 0;
84}
85EXPORT_SYMBOL_GPL(rds_page_copy_user);
86
87/*
88 * Message allocation uses this to build up regions of a message.
89 *
90 * @bytes - the number of bytes needed.
91 * @gfp - the waiting behaviour of the allocation
92 *
93 * @gfp is always ored with __GFP_HIGHMEM. Callers must be prepared to
94 * kmap the pages, etc.
95 *
96 * If @bytes is at least a full page then this just returns a page from
97 * alloc_page().
98 *
99 * If @bytes is a partial page then this stores the unused region of the
100 * page in a per-cpu structure. Future partial-page allocations may be
101 * satisfied from that cached region. This lets us waste less memory on
102 * small allocations with minimal complexity. It works because the transmit
103 * path passes read-only page regions down to devices. They hold a page
104 * reference until they are done with the region.
105 */
106int rds_page_remainder_alloc(struct scatterlist *scat, unsigned long bytes,
107                 gfp_t gfp)
108{
109    struct rds_page_remainder *rem;
110    unsigned long flags;
111    struct page *page;
112    int ret;
113
114    gfp |= __GFP_HIGHMEM;
115
116    /* jump straight to allocation if we're trying for a huge page */
117    if (bytes >= PAGE_SIZE) {
118        page = alloc_page(gfp);
119        if (page == NULL) {
120            ret = -ENOMEM;
121        } else {
122            sg_set_page(scat, page, PAGE_SIZE, 0);
123            ret = 0;
124        }
125        goto out;
126    }
127
128    rem = &per_cpu(rds_page_remainders, get_cpu());
129    local_irq_save(flags);
130
131    while (1) {
132        /* avoid a tiny region getting stuck by tossing it */
133        if (rem->r_page && bytes > (PAGE_SIZE - rem->r_offset)) {
134            rds_stats_inc(s_page_remainder_miss);
135            __free_page(rem->r_page);
136            rem->r_page = NULL;
137        }
138
139        /* hand out a fragment from the cached page */
140        if (rem->r_page && bytes <= (PAGE_SIZE - rem->r_offset)) {
141            sg_set_page(scat, rem->r_page, bytes, rem->r_offset);
142            get_page(sg_page(scat));
143
144            if (rem->r_offset != 0)
145                rds_stats_inc(s_page_remainder_hit);
146
147            rem->r_offset += bytes;
148            if (rem->r_offset == PAGE_SIZE) {
149                __free_page(rem->r_page);
150                rem->r_page = NULL;
151            }
152            ret = 0;
153            break;
154        }
155
156        /* alloc if there is nothing for us to use */
157        local_irq_restore(flags);
158        put_cpu();
159
160        page = alloc_page(gfp);
161
162        rem = &per_cpu(rds_page_remainders, get_cpu());
163        local_irq_save(flags);
164
165        if (page == NULL) {
166            ret = -ENOMEM;
167            break;
168        }
169
170        /* did someone race to fill the remainder before us? */
171        if (rem->r_page) {
172            __free_page(page);
173            continue;
174        }
175
176        /* otherwise install our page and loop around to alloc */
177        rem->r_page = page;
178        rem->r_offset = 0;
179    }
180
181    local_irq_restore(flags);
182    put_cpu();
183out:
184    rdsdebug("bytes %lu ret %d %p %u %u\n", bytes, ret,
185         ret ? NULL : sg_page(scat), ret ? 0 : scat->offset,
186         ret ? 0 : scat->length);
187    return ret;
188}
189
190static int rds_page_remainder_cpu_notify(struct notifier_block *self,
191                     unsigned long action, void *hcpu)
192{
193    struct rds_page_remainder *rem;
194    long cpu = (long)hcpu;
195
196    rem = &per_cpu(rds_page_remainders, cpu);
197
198    rdsdebug("cpu %ld action 0x%lx\n", cpu, action);
199
200    switch (action) {
201    case CPU_DEAD:
202        if (rem->r_page)
203            __free_page(rem->r_page);
204        rem->r_page = NULL;
205        break;
206    }
207
208    return 0;
209}
210
211static struct notifier_block rds_page_remainder_nb = {
212    .notifier_call = rds_page_remainder_cpu_notify,
213};
214
215void rds_page_exit(void)
216{
217    int i;
218
219    for_each_possible_cpu(i)
220        rds_page_remainder_cpu_notify(&rds_page_remainder_nb,
221                          (unsigned long)CPU_DEAD,
222                          (void *)(long)i);
223}
224

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