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 #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
  64 struct rds_info_iterator {
  65         struct page **pages;
  66         void *addr;
  67         unsigned long offset;
  68 };
  69
  70 static DEFINE_SPINLOCK(rds_info_lock);
  71 static rds_info_func rds_info_funcs[RDS_INFO_LAST - RDS_INFO_FIRST + 1];
  72
  73 void 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 }
  84 EXPORT_SYMBOL_GPL(rds_info_register_func);
  85
  86 void 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 }
  97 EXPORT_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  */
 104 void rds_info_iter_unmap(struct rds_info_iterator *iter)
 105 {
 106         if (iter->addr) {
 107                 kunmap_atomic(iter->addr, KM_USER0);
 108                 iter->addr = NULL;
 109         }
 110 }
 111
 112 /*
 113  * get_user_pages() called flush_dcache_page() on the pages for us.
 114  */
 115 void 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, KM_USER0);
 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, KM_USER0);
 138                         iter->addr = NULL;
 139                         iter->offset = 0;
 140                         iter->pages++;
 141                 }
 142         }
 143 }
 144 EXPORT_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  */
 158 int 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
 208 call_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
 237 out:
 238         for (i = 0; pages && i < nr_pages; i++)
 239                 put_page(pages[i]);
 240         kfree(pages);
 241
 242         return ret;
 243 }