dm-stripe.c revision af4874e03ed82f050d5872d8c39ce64bf16b5c38
1/* 2 * Copyright (C) 2001-2003 Sistina Software (UK) Limited. 3 * 4 * This file is released under the GPL. 5 */ 6 7#include <linux/device-mapper.h> 8 9#include <linux/module.h> 10#include <linux/init.h> 11#include <linux/blkdev.h> 12#include <linux/bio.h> 13#include <linux/slab.h> 14#include <linux/log2.h> 15 16#define DM_MSG_PREFIX "striped" 17#define DM_IO_ERROR_THRESHOLD 15 18 19struct stripe { 20 struct dm_dev *dev; 21 sector_t physical_start; 22 23 atomic_t error_count; 24}; 25 26struct stripe_c { 27 uint32_t stripes; 28 29 /* The size of this target / num. stripes */ 30 sector_t stripe_width; 31 32 /* stripe chunk size */ 33 uint32_t chunk_shift; 34 sector_t chunk_mask; 35 36 /* Needed for handling events */ 37 struct dm_target *ti; 38 39 /* Work struct used for triggering events*/ 40 struct work_struct kstriped_ws; 41 42 struct stripe stripe[0]; 43}; 44 45static struct workqueue_struct *kstriped; 46 47/* 48 * An event is triggered whenever a drive 49 * drops out of a stripe volume. 50 */ 51static void trigger_event(struct work_struct *work) 52{ 53 struct stripe_c *sc = container_of(work, struct stripe_c, kstriped_ws); 54 55 dm_table_event(sc->ti->table); 56 57} 58 59static inline struct stripe_c *alloc_context(unsigned int stripes) 60{ 61 size_t len; 62 63 if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe), 64 stripes)) 65 return NULL; 66 67 len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes); 68 69 return kmalloc(len, GFP_KERNEL); 70} 71 72/* 73 * Parse a single <dev> <sector> pair 74 */ 75static int get_stripe(struct dm_target *ti, struct stripe_c *sc, 76 unsigned int stripe, char **argv) 77{ 78 unsigned long long start; 79 80 if (sscanf(argv[1], "%llu", &start) != 1) 81 return -EINVAL; 82 83 if (dm_get_device(ti, argv[0], start, sc->stripe_width, 84 dm_table_get_mode(ti->table), 85 &sc->stripe[stripe].dev)) 86 return -ENXIO; 87 88 sc->stripe[stripe].physical_start = start; 89 90 return 0; 91} 92 93/* 94 * Construct a striped mapping. 95 * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+ 96 */ 97static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv) 98{ 99 struct stripe_c *sc; 100 sector_t width; 101 uint32_t stripes; 102 uint32_t chunk_size; 103 char *end; 104 int r; 105 unsigned int i; 106 107 if (argc < 2) { 108 ti->error = "Not enough arguments"; 109 return -EINVAL; 110 } 111 112 stripes = simple_strtoul(argv[0], &end, 10); 113 if (*end) { 114 ti->error = "Invalid stripe count"; 115 return -EINVAL; 116 } 117 118 chunk_size = simple_strtoul(argv[1], &end, 10); 119 if (*end) { 120 ti->error = "Invalid chunk_size"; 121 return -EINVAL; 122 } 123 124 /* 125 * chunk_size is a power of two 126 */ 127 if (!is_power_of_2(chunk_size) || 128 (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) { 129 ti->error = "Invalid chunk size"; 130 return -EINVAL; 131 } 132 133 if (ti->len & (chunk_size - 1)) { 134 ti->error = "Target length not divisible by " 135 "chunk size"; 136 return -EINVAL; 137 } 138 139 width = ti->len; 140 if (sector_div(width, stripes)) { 141 ti->error = "Target length not divisible by " 142 "number of stripes"; 143 return -EINVAL; 144 } 145 146 /* 147 * Do we have enough arguments for that many stripes ? 148 */ 149 if (argc != (2 + 2 * stripes)) { 150 ti->error = "Not enough destinations " 151 "specified"; 152 return -EINVAL; 153 } 154 155 sc = alloc_context(stripes); 156 if (!sc) { 157 ti->error = "Memory allocation for striped context " 158 "failed"; 159 return -ENOMEM; 160 } 161 162 INIT_WORK(&sc->kstriped_ws, trigger_event); 163 164 /* Set pointer to dm target; used in trigger_event */ 165 sc->ti = ti; 166 167 sc->stripes = stripes; 168 sc->stripe_width = width; 169 ti->split_io = chunk_size; 170 ti->num_flush_requests = stripes; 171 172 sc->chunk_mask = ((sector_t) chunk_size) - 1; 173 for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++) 174 chunk_size >>= 1; 175 sc->chunk_shift--; 176 177 /* 178 * Get the stripe destinations. 179 */ 180 for (i = 0; i < stripes; i++) { 181 argv += 2; 182 183 r = get_stripe(ti, sc, i, argv); 184 if (r < 0) { 185 ti->error = "Couldn't parse stripe destination"; 186 while (i--) 187 dm_put_device(ti, sc->stripe[i].dev); 188 kfree(sc); 189 return r; 190 } 191 atomic_set(&(sc->stripe[i].error_count), 0); 192 } 193 194 ti->private = sc; 195 196 return 0; 197} 198 199static void stripe_dtr(struct dm_target *ti) 200{ 201 unsigned int i; 202 struct stripe_c *sc = (struct stripe_c *) ti->private; 203 204 for (i = 0; i < sc->stripes; i++) 205 dm_put_device(ti, sc->stripe[i].dev); 206 207 flush_workqueue(kstriped); 208 kfree(sc); 209} 210 211static int stripe_map(struct dm_target *ti, struct bio *bio, 212 union map_info *map_context) 213{ 214 struct stripe_c *sc = (struct stripe_c *) ti->private; 215 sector_t offset, chunk; 216 uint32_t stripe; 217 218 if (unlikely(bio_empty_barrier(bio))) { 219 BUG_ON(map_context->flush_request >= sc->stripes); 220 bio->bi_bdev = sc->stripe[map_context->flush_request].dev->bdev; 221 return DM_MAPIO_REMAPPED; 222 } 223 224 offset = bio->bi_sector - ti->begin; 225 chunk = offset >> sc->chunk_shift; 226 stripe = sector_div(chunk, sc->stripes); 227 228 bio->bi_bdev = sc->stripe[stripe].dev->bdev; 229 bio->bi_sector = sc->stripe[stripe].physical_start + 230 (chunk << sc->chunk_shift) + (offset & sc->chunk_mask); 231 return DM_MAPIO_REMAPPED; 232} 233 234/* 235 * Stripe status: 236 * 237 * INFO 238 * #stripes [stripe_name <stripe_name>] [group word count] 239 * [error count 'A|D' <error count 'A|D'>] 240 * 241 * TABLE 242 * #stripes [stripe chunk size] 243 * [stripe_name physical_start <stripe_name physical_start>] 244 * 245 */ 246 247static int stripe_status(struct dm_target *ti, 248 status_type_t type, char *result, unsigned int maxlen) 249{ 250 struct stripe_c *sc = (struct stripe_c *) ti->private; 251 char buffer[sc->stripes + 1]; 252 unsigned int sz = 0; 253 unsigned int i; 254 255 switch (type) { 256 case STATUSTYPE_INFO: 257 DMEMIT("%d ", sc->stripes); 258 for (i = 0; i < sc->stripes; i++) { 259 DMEMIT("%s ", sc->stripe[i].dev->name); 260 buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ? 261 'D' : 'A'; 262 } 263 buffer[i] = '\0'; 264 DMEMIT("1 %s", buffer); 265 break; 266 267 case STATUSTYPE_TABLE: 268 DMEMIT("%d %llu", sc->stripes, 269 (unsigned long long)sc->chunk_mask + 1); 270 for (i = 0; i < sc->stripes; i++) 271 DMEMIT(" %s %llu", sc->stripe[i].dev->name, 272 (unsigned long long)sc->stripe[i].physical_start); 273 break; 274 } 275 return 0; 276} 277 278static int stripe_end_io(struct dm_target *ti, struct bio *bio, 279 int error, union map_info *map_context) 280{ 281 unsigned i; 282 char major_minor[16]; 283 struct stripe_c *sc = ti->private; 284 285 if (!error) 286 return 0; /* I/O complete */ 287 288 if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio)) 289 return error; 290 291 if (error == -EOPNOTSUPP) 292 return error; 293 294 memset(major_minor, 0, sizeof(major_minor)); 295 sprintf(major_minor, "%d:%d", 296 MAJOR(disk_devt(bio->bi_bdev->bd_disk)), 297 MINOR(disk_devt(bio->bi_bdev->bd_disk))); 298 299 /* 300 * Test to see which stripe drive triggered the event 301 * and increment error count for all stripes on that device. 302 * If the error count for a given device exceeds the threshold 303 * value we will no longer trigger any further events. 304 */ 305 for (i = 0; i < sc->stripes; i++) 306 if (!strcmp(sc->stripe[i].dev->name, major_minor)) { 307 atomic_inc(&(sc->stripe[i].error_count)); 308 if (atomic_read(&(sc->stripe[i].error_count)) < 309 DM_IO_ERROR_THRESHOLD) 310 queue_work(kstriped, &sc->kstriped_ws); 311 } 312 313 return error; 314} 315 316static int stripe_iterate_devices(struct dm_target *ti, 317 iterate_devices_callout_fn fn, void *data) 318{ 319 struct stripe_c *sc = ti->private; 320 int ret = 0; 321 unsigned i = 0; 322 323 do 324 ret = fn(ti, sc->stripe[i].dev, 325 sc->stripe[i].physical_start, data); 326 while (!ret && ++i < sc->stripes); 327 328 return ret; 329} 330 331static struct target_type stripe_target = { 332 .name = "striped", 333 .version = {1, 2, 0}, 334 .module = THIS_MODULE, 335 .ctr = stripe_ctr, 336 .dtr = stripe_dtr, 337 .map = stripe_map, 338 .end_io = stripe_end_io, 339 .status = stripe_status, 340 .iterate_devices = stripe_iterate_devices, 341}; 342 343int __init dm_stripe_init(void) 344{ 345 int r; 346 347 r = dm_register_target(&stripe_target); 348 if (r < 0) { 349 DMWARN("target registration failed"); 350 return r; 351 } 352 353 kstriped = create_singlethread_workqueue("kstriped"); 354 if (!kstriped) { 355 DMERR("failed to create workqueue kstriped"); 356 dm_unregister_target(&stripe_target); 357 return -ENOMEM; 358 } 359 360 return r; 361} 362 363void dm_stripe_exit(void) 364{ 365 dm_unregister_target(&stripe_target); 366 destroy_workqueue(kstriped); 367 368 return; 369} 370