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