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 %lu)", 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(void *data) 133 { 134 struct cn_msg *msg = (struct cn_msg *)data; 135 struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1); 136 137 spin_lock(&receiving_list_lock); 138 if (msg->len == 0) 139 fill_pkg(msg, NULL); 140 else if (msg->len < sizeof(*tfr)) 141 DMERR("Incomplete message received (expected %u, got %u): [%u]", 142 (unsigned)sizeof(*tfr), msg->len, msg->seq); 143 else 144 fill_pkg(NULL, tfr); 145 spin_unlock(&receiving_list_lock); 146 } 147 148 /** 149 * dm_consult_userspace 150 * @uuid: log's uuid (must be DM_UUID_LEN in size) 151 * @request_type: found in include/linux/dm-log-userspace.h 152 * @data: data to tx to the server 153 * @data_size: size of data in bytes 154 * @rdata: place to put return data from server 155 * @rdata_size: value-result (amount of space given/amount of space used) 156 * 157 * rdata_size is undefined on failure. 158 * 159 * Memory used to communicate with userspace is zero'ed 160 * before populating to ensure that no unwanted bits leak 161 * from kernel space to user-space. All userspace log communications 162 * between kernel and user space go through this function. 163 * 164 * Returns: 0 on success, -EXXX on failure 165 **/ 166 int dm_consult_userspace(const char *uuid, int request_type, 167 char *data, size_t data_size, 168 char *rdata, size_t *rdata_size) 169 { 170 int r = 0; 171 size_t dummy = 0; 172 int overhead_size = 173 sizeof(struct dm_ulog_request *) + sizeof(struct cn_msg); 174 struct dm_ulog_request *tfr = prealloced_ulog_tfr; 175 struct receiving_pkg pkg; 176 177 if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { 178 DMINFO("Size of tfr exceeds preallocated size"); 179 return -EINVAL; 180 } 181 182 if (!rdata_size) 183 rdata_size = &dummy; 184 resend: 185 /* 186 * We serialize the sending of requests so we can 187 * use the preallocated space. 188 */ 189 mutex_lock(&dm_ulog_lock); 190 191 memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - overhead_size); 192 memcpy(tfr->uuid, uuid, DM_UUID_LEN); 193 tfr->seq = dm_ulog_seq++; 194 195 /* 196 * Must be valid request type (all other bits set to 197 * zero). This reserves other bits for possible future 198 * use. 199 */ 200 tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; 201 202 tfr->data_size = data_size; 203 if (data && data_size) 204 memcpy(tfr->data, data, data_size); 205 206 memset(&pkg, 0, sizeof(pkg)); 207 init_completion(&pkg.complete); 208 pkg.seq = tfr->seq; 209 pkg.data_size = rdata_size; 210 pkg.data = rdata; 211 spin_lock(&receiving_list_lock); 212 list_add(&(pkg.list), &receiving_list); 213 spin_unlock(&receiving_list_lock); 214 215 r = dm_ulog_sendto_server(tfr); 216 217 mutex_unlock(&dm_ulog_lock); 218 219 if (r) { 220 DMERR("Unable to send log request [%u] to userspace: %d", 221 request_type, r); 222 spin_lock(&receiving_list_lock); 223 list_del_init(&(pkg.list)); 224 spin_unlock(&receiving_list_lock); 225 226 goto out; 227 } 228 229 r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); 230 spin_lock(&receiving_list_lock); 231 list_del_init(&(pkg.list)); 232 spin_unlock(&receiving_list_lock); 233 if (!r) { 234 DMWARN("[%s] Request timed out: [%u/%u] - retrying", 235 (strlen(uuid) > 8) ? 236 (uuid + (strlen(uuid) - 8)) : (uuid), 237 request_type, pkg.seq); 238 goto resend; 239 } 240 241 r = pkg.error; 242 if (r == -EAGAIN) 243 goto resend; 244 245 out: 246 return r; 247 } 248 249 int dm_ulog_tfr_init(void) 250 { 251 int r; 252 void *prealloced; 253 254 INIT_LIST_HEAD(&receiving_list); 255 256 prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); 257 if (!prealloced) 258 return -ENOMEM; 259 260 prealloced_cn_msg = prealloced; 261 prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); 262 263 r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); 264 if (r) { 265 cn_del_callback(&ulog_cn_id); 266 return r; 267 } 268 269 return 0; 270 } 271 272 void dm_ulog_tfr_exit(void) 273 { 274 cn_del_callback(&ulog_cn_id); 275 kfree(prealloced_cn_msg); 276 } 277