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
  63 struct rds_info_iterator {
  64         struct page **pages;
  65         void *addr;
  66         unsigned long offset;
  67 };
  68
  69 static DEFINE_SPINLOCK(rds_info_lock);
  70 static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
  71
  72 void 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]);
  80         rds_info_funcs[offset] = func;
  81         spin_unlock(&rds_info_lock);
  82 }
  83 EXPORT_SYMBOL_GPL(rds_info_register_func);
  84
  85 void 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 }
  96 EXPORT_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  */
 103 void rds_info_iter_unmap(struct rds_info_iterator *iter)
 104 {
 105         if (iter->addr) {
 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  */
 114 void 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)
 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 }
 143 EXPORT_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  */
 157 int 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) {
 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
 207 call_func:
 208         func = rds_info_funcs[optname - RDS_INFO_FIRST];
 209         if (!func) {
 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
 236 out:
 237         for (i = 0; pages && i < nr_pages; i++)
 238                 put_page(pages[i]);
 239         kfree(pages);
 240
 241         return ret;
 242 }