Root/net/rds/info.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/percpu.h>
34#include <linux/seq_file.h>
35#include <linux/slab.h>
36#include <linux/proc_fs.h>
37
38#include "rds.h"
39
40/*
41 * This file implements a getsockopt() call which copies a set of fixed
42 * sized structs into a user-specified buffer as a means of providing
43 * read-only information about RDS.
44 *
45 * For a given information source there are a given number of fixed sized
46 * structs at a given time. The structs are only copied if the user-specified
47 * buffer is big enough. The destination pages that make up the buffer
48 * are pinned for the duration of the copy.
49 *
50 * This gives us the following benefits:
51 *
52 * - simple implementation, no copy "position" across multiple calls
53 * - consistent snapshot of an info source
54 * - atomic copy works well with whatever locking info source has
55 * - one portable tool to get rds info across implementations
56 * - long-lived tool can get info without allocating
57 *
58 * at the following costs:
59 *
60 * - info source copy must be pinned, may be "large"
61 */
62
63struct rds_info_iterator {
64    struct page **pages;
65    void *addr;
66    unsigned long offset;
67};
68
69static DEFINE_SPINLOCK(rds_info_lock);
70static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
71
72void rds_info_register_func(int optname, rds_info_func func)
73{
74    int offset = optname - RDS_INFO_FIRST;
75
76    BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
77
78    spin_lock(&rds_info_lock);
79    BUG_ON(rds_info_funcs[offset] != NULL);
80    rds_info_funcs[offset] = func;
81    spin_unlock(&rds_info_lock);
82}
83EXPORT_SYMBOL_GPL(rds_info_register_func);
84
85void rds_info_deregister_func(int optname, rds_info_func func)
86{
87    int offset = optname - RDS_INFO_FIRST;
88
89    BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
90
91    spin_lock(&rds_info_lock);
92    BUG_ON(rds_info_funcs[offset] != func);
93    rds_info_funcs[offset] = NULL;
94    spin_unlock(&rds_info_lock);
95}
96EXPORT_SYMBOL_GPL(rds_info_deregister_func);
97
98/*
99 * Typically we hold an atomic kmap across multiple rds_info_copy() calls
100 * because the kmap is so expensive. This must be called before using blocking
101 * operations while holding the mapping and as the iterator is torn down.
102 */
103void rds_info_iter_unmap(struct rds_info_iterator *iter)
104{
105    if (iter->addr != NULL) {
106        kunmap_atomic(iter->addr, KM_USER0);
107        iter->addr = NULL;
108    }
109}
110
111/*
112 * get_user_pages() called flush_dcache_page() on the pages for us.
113 */
114void rds_info_copy(struct rds_info_iterator *iter, void *data,
115           unsigned long bytes)
116{
117    unsigned long this;
118
119    while (bytes) {
120        if (iter->addr == NULL)
121            iter->addr = kmap_atomic(*iter->pages, KM_USER0);
122
123        this = min(bytes, PAGE_SIZE - iter->offset);
124
125        rdsdebug("page %p addr %p offset %lu this %lu data %p "
126              "bytes %lu\n", *iter->pages, iter->addr,
127              iter->offset, this, data, bytes);
128
129        memcpy(iter->addr + iter->offset, data, this);
130
131        data += this;
132        bytes -= this;
133        iter->offset += this;
134
135        if (iter->offset == PAGE_SIZE) {
136            kunmap_atomic(iter->addr, KM_USER0);
137            iter->addr = NULL;
138            iter->offset = 0;
139            iter->pages++;
140        }
141    }
142}
143EXPORT_SYMBOL_GPL(rds_info_copy);
144
145/*
146 * @optval points to the userspace buffer that the information snapshot
147 * will be copied into.
148 *
149 * @optlen on input is the size of the buffer in userspace. @optlen
150 * on output is the size of the requested snapshot in bytes.
151 *
152 * This function returns -errno if there is a failure, particularly -ENOSPC
153 * if the given userspace buffer was not large enough to fit the snapshot.
154 * On success it returns the positive number of bytes of each array element
155 * in the snapshot.
156 */
157int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
158            int __user *optlen)
159{
160    struct rds_info_iterator iter;
161    struct rds_info_lengths lens;
162    unsigned long nr_pages = 0;
163    unsigned long start;
164    unsigned long i;
165    rds_info_func func;
166    struct page **pages = NULL;
167    int ret;
168    int len;
169    int total;
170
171    if (get_user(len, optlen)) {
172        ret = -EFAULT;
173        goto out;
174    }
175
176    /* check for all kinds of wrapping and the like */
177    start = (unsigned long)optval;
178    if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
179        ret = -EINVAL;
180        goto out;
181    }
182
183    /* a 0 len call is just trying to probe its length */
184    if (len == 0)
185        goto call_func;
186
187    nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
188            >> PAGE_SHIFT;
189
190    pages = kmalloc(nr_pages * sizeof(struct page *), GFP_KERNEL);
191    if (pages == NULL) {
192        ret = -ENOMEM;
193        goto out;
194    }
195    ret = get_user_pages_fast(start, nr_pages, 1, pages);
196    if (ret != nr_pages) {
197        if (ret > 0)
198            nr_pages = ret;
199        else
200            nr_pages = 0;
201        ret = -EAGAIN; /* XXX ? */
202        goto out;
203    }
204
205    rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
206
207call_func:
208    func = rds_info_funcs[optname - RDS_INFO_FIRST];
209    if (func == NULL) {
210        ret = -ENOPROTOOPT;
211        goto out;
212    }
213
214    iter.pages = pages;
215    iter.addr = NULL;
216    iter.offset = start & (PAGE_SIZE - 1);
217
218    func(sock, len, &iter, &lens);
219    BUG_ON(lens.each == 0);
220
221    total = lens.nr * lens.each;
222
223    rds_info_iter_unmap(&iter);
224
225    if (total > len) {
226        len = total;
227        ret = -ENOSPC;
228    } else {
229        len = total;
230        ret = lens.each;
231    }
232
233    if (put_user(len, optlen))
234        ret = -EFAULT;
235
236out:
237    for (i = 0; pages != NULL && i < nr_pages; i++)
238        put_page(pages[i]);
239    kfree(pages);
240
241    return ret;
242}
243

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