drivers/md/dm-log-userspace-transfer.c

   1 /*
   2  * Copyright (C) 2006-2009 Red Hat, Inc.
   3  *
   4  * This file is released under the LGPL.
   5  */
   6
   7 #include <linux/kernel.h>
   8 #include <linux/module.h>
   9 #include <linux/slab.h>
  10 #include <net/sock.h>
  11 #include <linux/workqueue.h>
  12 #include <linux/connector.h>
  13 #include <linux/device-mapper.h>
  14 #include <linux/dm-log-userspace.h>
  15
  16 #include "dm-log-userspace-transfer.h"
  17
  18 static uint32_t dm_ulog_seq;
  19
  20 /*
  21  * Netlink/Connector is an unreliable protocol.  How long should
  22  * we wait for a response before assuming it was lost and retrying?
  23  * (If we do receive a response after this time, it will be discarded
  24  * and the response to the resent request will be waited for.
  25  */
  26 #define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
  27
  28 /*
  29  * Pre-allocated space for speed
  30  */
  31 #define DM_ULOG_PREALLOCED_SIZE 512
  32 static struct cn_msg *prealloced_cn_msg;
  33 static struct dm_ulog_request *prealloced_ulog_tfr;
  34
  35 static struct cb_id ulog_cn_id = {
  36         .idx = CN_IDX_DM,
  37         .val = CN_VAL_DM_USERSPACE_LOG
  38 };
  39
  40 static DEFINE_MUTEX(dm_ulog_lock);
  41
  42 struct receiving_pkg {
  43         struct list_head list;
  44         struct completion complete;
  45
  46         uint32_t seq;
  47
  48         int error;
  49         size_t *data_size;
  50         char *data;
  51 };
  52
  53 static DEFINE_SPINLOCK(receiving_list_lock);
  54 static struct list_head receiving_list;
  55
  56 static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
  57 {
  58         int r;
  59         struct cn_msg *msg = prealloced_cn_msg;
  60
  61         memset(msg, 0, sizeof(struct cn_msg));
  62
  63         msg->id.idx = ulog_cn_id.idx;
  64         msg->id.val = ulog_cn_id.val;
  65         msg->ack = 0;
  66         msg->seq = tfr->seq;
  67         msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
  68
  69         r = cn_netlink_send(msg, 0, gfp_any());
  70
  71         return r;
  72 }
  73
  74 /*
  75  * Parameters for this function can be either msg or tfr, but not
  76  * both.  This function fills in the reply for a waiting request.
  77  * If just msg is given, then the reply is simply an ACK from userspace
  78  * that the request was received.
  79  *
  80  * Returns: 0 on success, -ENOENT on failure
  81  */
  82 static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
  83 {
  84         uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
  85         struct receiving_pkg *pkg;
  86
  87         /*
  88          * The 'receiving_pkg' entries in this list are statically
  89          * allocated on the stack in 'dm_consult_userspace'.
  90          * Each process that is waiting for a reply from the user
  91          * space server will have an entry in this list.
  92          *
  93          * We are safe to do it this way because the stack space
  94          * is unique to each process, but still addressable by
  95          * other processes.
  96          */
  97         list_for_each_entry(pkg, &receiving_list, list) {
  98                 if (rtn_seq != pkg->seq)
  99                         continue;
 100
 101                 if (msg) {
 102                         pkg->error = -msg->ack;
 103                         /*
 104                          * If we are trying again, we will need to know our
 105                          * storage capacity.  Otherwise, along with the
 106                          * error code, we make explicit that we have no data.
 107                          */
 108                         if (pkg->error != -EAGAIN)
 109                                 *(pkg->data_size) = 0;
 110                 } else if (tfr->data_size > *(pkg->data_size)) {
 111                         DMERR("Insufficient space to receive package [%u] "
 112                               "(%u vs %zu)", tfr->request_type,
 113                               tfr->data_size, *(pkg->data_size));
 114
 115                         *(pkg->data_size) = 0;
 116                         pkg->error = -ENOSPC;
 117                 } else {
 118                         pkg->error = tfr->error;
 119                         memcpy(pkg->data, tfr->data, tfr->data_size);
 120                         *(pkg->data_size) = tfr->data_size;
 121                 }
 122                 complete(&pkg->complete);
 123                 return 0;
 124         }
 125
 126         return -ENOENT;
 127 }
 128
 129 /*
 130  * This is the connector callback that delivers data
 131  * that was sent from userspace.
 132  */
 133 static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
 134 {
 135         struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
 136
 137         if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
 138                 return;
 139
 140         spin_lock(&receiving_list_lock);
 141         if (msg->len == 0)
 142                 fill_pkg(msg, NULL);
 143         else if (msg->len < sizeof(*tfr))
 144                 DMERR("Incomplete message received (expected %u, got %u): [%u]",
 145                       (unsigned)sizeof(*tfr), msg->len, msg->seq);
 146         else
 147                 fill_pkg(NULL, tfr);
 148         spin_unlock(&receiving_list_lock);
 149 }
 150
 151 /**
 152  * dm_consult_userspace
 153  * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
 154  * @luid: log's local unique identifier
 155  * @request_type:  found in include/linux/dm-log-userspace.h
 156  * @data: data to tx to the server
 157  * @data_size: size of data in bytes
 158  * @rdata: place to put return data from server
 159  * @rdata_size: value-result (amount of space given/amount of space used)
 160  *
 161  * rdata_size is undefined on failure.
 162  *
 163  * Memory used to communicate with userspace is zero'ed
 164  * before populating to ensure that no unwanted bits leak
 165  * from kernel space to user-space.  All userspace log communications
 166  * between kernel and user space go through this function.
 167  *
 168  * Returns: 0 on success, -EXXX on failure
 169  **/
 170 int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
 171                          char *data, size_t data_size,
 172                          char *rdata, size_t *rdata_size)
 173 {
 174         int r = 0;
 175         size_t dummy = 0;
 176         int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
 177         struct dm_ulog_request *tfr = prealloced_ulog_tfr;
 178         struct receiving_pkg pkg;
 179
 180         /*
 181          * Given the space needed to hold the 'struct cn_msg' and
 182          * 'struct dm_ulog_request' - do we have enough payload
 183          * space remaining?
 184          */
 185         if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
 186                 DMINFO("Size of tfr exceeds preallocated size");
 187                 return -EINVAL;
 188         }
 189
 190         if (!rdata_size)
 191                 rdata_size = &dummy;
 192 resend:
 193         /*
 194          * We serialize the sending of requests so we can
 195          * use the preallocated space.
 196          */
 197         mutex_lock(&dm_ulog_lock);
 198
 199         memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
 200         memcpy(tfr->uuid, uuid, DM_UUID_LEN);
 201         tfr->version = DM_ULOG_REQUEST_VERSION;
 202         tfr->luid = luid;
 203         tfr->seq = dm_ulog_seq++;
 204
 205         /*
 206          * Must be valid request type (all other bits set to
 207          * zero).  This reserves other bits for possible future
 208          * use.
 209          */
 210         tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
 211
 212         tfr->data_size = data_size;
 213         if (data && data_size)
 214                 memcpy(tfr->data, data, data_size);
 215
 216         memset(&pkg, 0, sizeof(pkg));
 217         init_completion(&pkg.complete);
 218         pkg.seq = tfr->seq;
 219         pkg.data_size = rdata_size;
 220         pkg.data = rdata;
 221         spin_lock(&receiving_list_lock);
 222         list_add(&(pkg.list), &receiving_list);
 223         spin_unlock(&receiving_list_lock);
 224
 225         r = dm_ulog_sendto_server(tfr);
 226
 227         mutex_unlock(&dm_ulog_lock);
 228
 229         if (r) {
 230                 DMERR("Unable to send log request [%u] to userspace: %d",
 231                       request_type, r);
 232                 spin_lock(&receiving_list_lock);
 233                 list_del_init(&(pkg.list));
 234                 spin_unlock(&receiving_list_lock);
 235
 236                 goto out;
 237         }
 238
 239         r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
 240         spin_lock(&receiving_list_lock);
 241         list_del_init(&(pkg.list));
 242         spin_unlock(&receiving_list_lock);
 243         if (!r) {
 244                 DMWARN("[%s] Request timed out: [%u/%u] - retrying",
 245                        (strlen(uuid) > 8) ?
 246                        (uuid + (strlen(uuid) - 8)) : (uuid),
 247                        request_type, pkg.seq);
 248                 goto resend;
 249         }
 250
 251         r = pkg.error;
 252         if (r == -EAGAIN)
 253                 goto resend;
 254
 255 out:
 256         return r;
 257 }
 258
 259 int dm_ulog_tfr_init(void)
 260 {
 261         int r;
 262         void *prealloced;
 263
 264         INIT_LIST_HEAD(&receiving_list);
 265
 266         prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
 267         if (!prealloced)
 268                 return -ENOMEM;
 269
 270         prealloced_cn_msg = prealloced;
 271         prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
 272
 273         r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
 274         if (r) {
 275                 cn_del_callback(&ulog_cn_id);
 276                 return r;
 277         }
 278
 279         return 0;
 280 }
 281
 282 void dm_ulog_tfr_exit(void)
 283 {
 284         cn_del_callback(&ulog_cn_id);
 285         kfree(prealloced_cn_msg);
 286 }