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 18static 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 32static struct cn_msg *prealloced_cn_msg; 33static struct dm_ulog_request *prealloced_ulog_tfr; 34 35static struct cb_id ulog_cn_id = { 36 .idx = CN_IDX_DM, 37 .val = CN_VAL_DM_USERSPACE_LOG 38}; 39 40static DEFINE_MUTEX(dm_ulog_lock); 41 42struct 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 53static DEFINE_SPINLOCK(receiving_list_lock); 54static struct list_head receiving_list; 55 56static 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 */ 82static 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 */ 133static 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(nsp->eff_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 **/ 170int 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; 192resend: 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->luid = luid; 202 tfr->seq = dm_ulog_seq++; 203 204 /* 205 * Must be valid request type (all other bits set to 206 * zero). This reserves other bits for possible future 207 * use. 208 */ 209 tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; 210 211 tfr->data_size = data_size; 212 if (data && data_size) 213 memcpy(tfr->data, data, data_size); 214 215 memset(&pkg, 0, sizeof(pkg)); 216 init_completion(&pkg.complete); 217 pkg.seq = tfr->seq; 218 pkg.data_size = rdata_size; 219 pkg.data = rdata; 220 spin_lock(&receiving_list_lock); 221 list_add(&(pkg.list), &receiving_list); 222 spin_unlock(&receiving_list_lock); 223 224 r = dm_ulog_sendto_server(tfr); 225 226 mutex_unlock(&dm_ulog_lock); 227 228 if (r) { 229 DMERR("Unable to send log request [%u] to userspace: %d", 230 request_type, r); 231 spin_lock(&receiving_list_lock); 232 list_del_init(&(pkg.list)); 233 spin_unlock(&receiving_list_lock); 234 235 goto out; 236 } 237 238 r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); 239 spin_lock(&receiving_list_lock); 240 list_del_init(&(pkg.list)); 241 spin_unlock(&receiving_list_lock); 242 if (!r) { 243 DMWARN("[%s] Request timed out: [%u/%u] - retrying", 244 (strlen(uuid) > 8) ? 245 (uuid + (strlen(uuid) - 8)) : (uuid), 246 request_type, pkg.seq); 247 goto resend; 248 } 249 250 r = pkg.error; 251 if (r == -EAGAIN) 252 goto resend; 253 254out: 255 return r; 256} 257 258int dm_ulog_tfr_init(void) 259{ 260 int r; 261 void *prealloced; 262 263 INIT_LIST_HEAD(&receiving_list); 264 265 prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); 266 if (!prealloced) 267 return -ENOMEM; 268 269 prealloced_cn_msg = prealloced; 270 prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); 271 272 r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); 273 if (r) { 274 cn_del_callback(&ulog_cn_id); 275 return r; 276 } 277 278 return 0; 279} 280 281void dm_ulog_tfr_exit(void) 282{ 283 cn_del_callback(&ulog_cn_id); 284 kfree(prealloced_cn_msg); 285} 286