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(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 universal unique identifier (must be DM_UUID_LEN in size) 151 * @luid: log's local unique identifier 152 * @request_type: found in include/linux/dm-log-userspace.h 153 * @data: data to tx to the server 154 * @data_size: size of data in bytes 155 * @rdata: place to put return data from server 156 * @rdata_size: value-result (amount of space given/amount of space used) 157 * 158 * rdata_size is undefined on failure. 159 * 160 * Memory used to communicate with userspace is zero'ed 161 * before populating to ensure that no unwanted bits leak 162 * from kernel space to user-space. All userspace log communications 163 * between kernel and user space go through this function. 164 * 165 * Returns: 0 on success, -EXXX on failure 166 **/ 167 int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type, 168 char *data, size_t data_size, 169 char *rdata, size_t *rdata_size) 170 { 171 int r = 0; 172 size_t dummy = 0; 173 int overhead_size = 174 sizeof(struct dm_ulog_request *) + sizeof(struct cn_msg); 175 struct dm_ulog_request *tfr = prealloced_ulog_tfr; 176 struct receiving_pkg pkg; 177 178 if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { 179 DMINFO("Size of tfr exceeds preallocated size"); 180 return -EINVAL; 181 } 182 183 if (!rdata_size) 184 rdata_size = &dummy; 185 resend: 186 /* 187 * We serialize the sending of requests so we can 188 * use the preallocated space. 189 */ 190 mutex_lock(&dm_ulog_lock); 191 192 memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - overhead_size); 193 memcpy(tfr->uuid, uuid, DM_UUID_LEN); 194 tfr->luid = luid; 195 tfr->seq = dm_ulog_seq++; 196 197 /* 198 * Must be valid request type (all other bits set to 199 * zero). This reserves other bits for possible future 200 * use. 201 */ 202 tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; 203 204 tfr->data_size = data_size; 205 if (data && data_size) 206 memcpy(tfr->data, data, data_size); 207 208 memset(&pkg, 0, sizeof(pkg)); 209 init_completion(&pkg.complete); 210 pkg.seq = tfr->seq; 211 pkg.data_size = rdata_size; 212 pkg.data = rdata; 213 spin_lock(&receiving_list_lock); 214 list_add(&(pkg.list), &receiving_list); 215 spin_unlock(&receiving_list_lock); 216 217 r = dm_ulog_sendto_server(tfr); 218 219 mutex_unlock(&dm_ulog_lock); 220 221 if (r) { 222 DMERR("Unable to send log request [%u] to userspace: %d", 223 request_type, r); 224 spin_lock(&receiving_list_lock); 225 list_del_init(&(pkg.list)); 226 spin_unlock(&receiving_list_lock); 227 228 goto out; 229 } 230 231 r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); 232 spin_lock(&receiving_list_lock); 233 list_del_init(&(pkg.list)); 234 spin_unlock(&receiving_list_lock); 235 if (!r) { 236 DMWARN("[%s] Request timed out: [%u/%u] - retrying", 237 (strlen(uuid) > 8) ? 238 (uuid + (strlen(uuid) - 8)) : (uuid), 239 request_type, pkg.seq); 240 goto resend; 241 } 242 243 r = pkg.error; 244 if (r == -EAGAIN) 245 goto resend; 246 247 out: 248 return r; 249 } 250 251 int dm_ulog_tfr_init(void) 252 { 253 int r; 254 void *prealloced; 255 256 INIT_LIST_HEAD(&receiving_list); 257 258 prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); 259 if (!prealloced) 260 return -ENOMEM; 261 262 prealloced_cn_msg = prealloced; 263 prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); 264 265 r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); 266 if (r) { 267 cn_del_callback(&ulog_cn_id); 268 return r; 269 } 270 271 return 0; 272 } 273 274 void dm_ulog_tfr_exit(void) 275 { 276 cn_del_callback(&ulog_cn_id); 277 kfree(prealloced_cn_msg); 278 } 279