linux/net/rds/info.c
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   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#include <linux/export.h>
  38
  39#include "rds.h"
  40
  41/*
  42 * This file implements a getsockopt() call which copies a set of fixed
  43 * sized structs into a user-specified buffer as a means of providing
  44 * read-only information about RDS.
  45 *
  46 * For a given information source there are a given number of fixed sized
  47 * structs at a given time.  The structs are only copied if the user-specified
  48 * buffer is big enough.  The destination pages that make up the buffer
  49 * are pinned for the duration of the copy.
  50 *
  51 * This gives us the following benefits:
  52 *
  53 * - simple implementation, no copy "position" across multiple calls
  54 * - consistent snapshot of an info source
  55 * - atomic copy works well with whatever locking info source has
  56 * - one portable tool to get rds info across implementations
  57 * - long-lived tool can get info without allocating
  58 *
  59 * at the following costs:
  60 *
  61 * - info source copy must be pinned, may be "large"
  62 */
  63
  64struct rds_info_iterator {
  65        struct page **pages;
  66        void *addr;
  67        unsigned long offset;
  68};
  69
  70static DEFINE_SPINLOCK(rds_info_lock);
  71static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
  72
  73void rds_info_register_func(int optname, rds_info_func func)
  74{
  75        int offset = optname - RDS_INFO_FIRST;
  76
  77        BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
  78
  79        spin_lock(&rds_info_lock);
  80        BUG_ON(rds_info_funcs[offset]);
  81        rds_info_funcs[offset] = func;
  82        spin_unlock(&rds_info_lock);
  83}
  84EXPORT_SYMBOL_GPL(rds_info_register_func);
  85
  86void rds_info_deregister_func(int optname, rds_info_func func)
  87{
  88        int offset = optname - RDS_INFO_FIRST;
  89
  90        BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST);
  91
  92        spin_lock(&rds_info_lock);
  93        BUG_ON(rds_info_funcs[offset] != func);
  94        rds_info_funcs[offset] = NULL;
  95        spin_unlock(&rds_info_lock);
  96}
  97EXPORT_SYMBOL_GPL(rds_info_deregister_func);
  98
  99/*
 100 * Typically we hold an atomic kmap across multiple rds_info_copy() calls
 101 * because the kmap is so expensive.  This must be called before using blocking
 102 * operations while holding the mapping and as the iterator is torn down.
 103 */
 104void rds_info_iter_unmap(struct rds_info_iterator *iter)
 105{
 106        if (iter->addr) {
 107                kunmap_atomic(iter->addr);
 108                iter->addr = NULL;
 109        }
 110}
 111
 112/*
 113 * get_user_pages() called flush_dcache_page() on the pages for us.
 114 */
 115void rds_info_copy(struct rds_info_iterator *iter, void *data,
 116                   unsigned long bytes)
 117{
 118        unsigned long this;
 119
 120        while (bytes) {
 121                if (!iter->addr)
 122                        iter->addr = kmap_atomic(*iter->pages);
 123
 124                this = min(bytes, PAGE_SIZE - iter->offset);
 125
 126                rdsdebug("page %p addr %p offset %lu this %lu data %p "
 127                          "bytes %lu\n", *iter->pages, iter->addr,
 128                          iter->offset, this, data, bytes);
 129
 130                memcpy(iter->addr + iter->offset, data, this);
 131
 132                data += this;
 133                bytes -= this;
 134                iter->offset += this;
 135
 136                if (iter->offset == PAGE_SIZE) {
 137                        kunmap_atomic(iter->addr);
 138                        iter->addr = NULL;
 139                        iter->offset = 0;
 140                        iter->pages++;
 141                }
 142        }
 143}
 144EXPORT_SYMBOL_GPL(rds_info_copy);
 145
 146/*
 147 * @optval points to the userspace buffer that the information snapshot
 148 * will be copied into.
 149 *
 150 * @optlen on input is the size of the buffer in userspace.  @optlen
 151 * on output is the size of the requested snapshot in bytes.
 152 *
 153 * This function returns -errno if there is a failure, particularly -ENOSPC
 154 * if the given userspace buffer was not large enough to fit the snapshot.
 155 * On success it returns the positive number of bytes of each array element
 156 * in the snapshot.
 157 */
 158int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
 159                        int __user *optlen)
 160{
 161        struct rds_info_iterator iter;
 162        struct rds_info_lengths lens;
 163        unsigned long nr_pages = 0;
 164        unsigned long start;
 165        unsigned long i;
 166        rds_info_func func;
 167        struct page **pages = NULL;
 168        int ret;
 169        int len;
 170        int total;
 171
 172        if (get_user(len, optlen)) {
 173                ret = -EFAULT;
 174                goto out;
 175        }
 176
 177        /* check for all kinds of wrapping and the like */
 178        start = (unsigned long)optval;
 179        if (len < 0 || len + PAGE_SIZE - 1 < len || start + len < start) {
 180                ret = -EINVAL;
 181                goto out;
 182        }
 183
 184        /* a 0 len call is just trying to probe its length */
 185        if (len == 0)
 186                goto call_func;
 187
 188        nr_pages = (PAGE_ALIGN(start + len) - (start & PAGE_MASK))
 189                        >> PAGE_SHIFT;
 190
 191        pages = kmalloc(nr_pages * sizeof(struct page *), GFP_KERNEL);
 192        if (!pages) {
 193                ret = -ENOMEM;
 194                goto out;
 195        }
 196        ret = get_user_pages_fast(start, nr_pages, 1, pages);
 197        if (ret != nr_pages) {
 198                if (ret > 0)
 199                        nr_pages = ret;
 200                else
 201                        nr_pages = 0;
 202                ret = -EAGAIN; /* XXX ? */
 203                goto out;
 204        }
 205
 206        rdsdebug("len %d nr_pages %lu\n", len, nr_pages);
 207
 208call_func:
 209        func = rds_info_funcs[optname - RDS_INFO_FIRST];
 210        if (!func) {
 211                ret = -ENOPROTOOPT;
 212                goto out;
 213        }
 214
 215        iter.pages = pages;
 216        iter.addr = NULL;
 217        iter.offset = start & (PAGE_SIZE - 1);
 218
 219        func(sock, len, &iter, &lens);
 220        BUG_ON(lens.each == 0);
 221
 222        total = lens.nr * lens.each;
 223
 224        rds_info_iter_unmap(&iter);
 225
 226        if (total > len) {
 227                len = total;
 228                ret = -ENOSPC;
 229        } else {
 230                len = total;
 231                ret = lens.each;
 232        }
 233
 234        if (put_user(len, optlen))
 235                ret = -EFAULT;
 236
 237out:
 238        for (i = 0; pages && i < nr_pages; i++)
 239                put_page(pages[i]);
 240        kfree(pages);
 241
 242        return ret;
 243}
 244
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