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