drivers/md/dm-flakey.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software (UK) Limited.
   3  * Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/blkdev.h>
  13 #include <linux/bio.h>
  14 #include <linux/slab.h>
  15
  16 #define DM_MSG_PREFIX "flakey"
  17
  18 #define all_corrupt_bio_flags_match(bio, fc)    \
  19         (((bio)->bi_rw & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
  20
  21 /*
  22  * Flakey: Used for testing only, simulates intermittent,
  23  * catastrophic device failure.
  24  */
  25 struct flakey_c {
  26         struct dm_dev *dev;
  27         unsigned long start_time;
  28         sector_t start;
  29         unsigned up_interval;
  30         unsigned down_interval;
  31         unsigned long flags;
  32         unsigned corrupt_bio_byte;
  33         unsigned corrupt_bio_rw;
  34         unsigned corrupt_bio_value;
  35         unsigned corrupt_bio_flags;
  36 };
  37
  38 enum feature_flag_bits {
  39         DROP_WRITES
  40 };
  41
  42 struct per_bio_data {
  43         bool bio_submitted;
  44 };
  45
  46 static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
  47                           struct dm_target *ti)
  48 {
  49         int r;
  50         unsigned argc;
  51         const char *arg_name;
  52
  53         static struct dm_arg _args[] = {
  54                 {0, 6, "Invalid number of feature args"},
  55                 {1, UINT_MAX, "Invalid corrupt bio byte"},
  56                 {0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
  57                 {0, UINT_MAX, "Invalid corrupt bio flags mask"},
  58         };
  59
  60         /* No feature arguments supplied. */
  61         if (!as->argc)
  62                 return 0;
  63
  64         r = dm_read_arg_group(_args, as, &argc, &ti->error);
  65         if (r)
  66                 return r;
  67
  68         while (argc) {
  69                 arg_name = dm_shift_arg(as);
  70                 argc--;
  71
  72                 /*
  73                  * drop_writes
  74                  */
  75                 if (!strcasecmp(arg_name, "drop_writes")) {
  76                         if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
  77                                 ti->error = "Feature drop_writes duplicated";
  78                                 return -EINVAL;
  79                         }
  80
  81                         continue;
  82                 }
  83
  84                 /*
  85                  * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
  86                  */
  87                 if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
  88                         if (!argc) {
  89                                 ti->error = "Feature corrupt_bio_byte requires parameters";
  90                                 return -EINVAL;
  91                         }
  92
  93                         r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
  94                         if (r)
  95                                 return r;
  96                         argc--;
  97
  98                         /*
  99                          * Direction r or w?
 100                          */
 101                         arg_name = dm_shift_arg(as);
 102                         if (!strcasecmp(arg_name, "w"))
 103                                 fc->corrupt_bio_rw = WRITE;
 104                         else if (!strcasecmp(arg_name, "r"))
 105                                 fc->corrupt_bio_rw = READ;
 106                         else {
 107                                 ti->error = "Invalid corrupt bio direction (r or w)";
 108                                 return -EINVAL;
 109                         }
 110                         argc--;
 111
 112                         /*
 113                          * Value of byte (0-255) to write in place of correct one.
 114                          */
 115                         r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
 116                         if (r)
 117                                 return r;
 118                         argc--;
 119
 120                         /*
 121                          * Only corrupt bios with these flags set.
 122                          */
 123                         r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
 124                         if (r)
 125                                 return r;
 126                         argc--;
 127
 128                         continue;
 129                 }
 130
 131                 ti->error = "Unrecognised flakey feature requested";
 132                 return -EINVAL;
 133         }
 134
 135         if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
 136                 ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
 137                 return -EINVAL;
 138         }
 139
 140         return 0;
 141 }
 142
 143 /*
 144  * Construct a flakey mapping:
 145  * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
 146  *
 147  *   Feature args:
 148  *     [drop_writes]
 149  *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
 150  *
 151  *   Nth_byte starts from 1 for the first byte.
 152  *   Direction is r for READ or w for WRITE.
 153  *   bio_flags is ignored if 0.
 154  */
 155 static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 156 {
 157         static struct dm_arg _args[] = {
 158                 {0, UINT_MAX, "Invalid up interval"},
 159                 {0, UINT_MAX, "Invalid down interval"},
 160         };
 161
 162         int r;
 163         struct flakey_c *fc;
 164         unsigned long long tmpll;
 165         struct dm_arg_set as;
 166         const char *devname;
 167         char dummy;
 168
 169         as.argc = argc;
 170         as.argv = argv;
 171
 172         if (argc < 4) {
 173                 ti->error = "Invalid argument count";
 174                 return -EINVAL;
 175         }
 176
 177         fc = kzalloc(sizeof(*fc), GFP_KERNEL);
 178         if (!fc) {
 179                 ti->error = "Cannot allocate context";
 180                 return -ENOMEM;
 181         }
 182         fc->start_time = jiffies;
 183
 184         devname = dm_shift_arg(&as);
 185
 186         r = -EINVAL;
 187         if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1) {
 188                 ti->error = "Invalid device sector";
 189                 goto bad;
 190         }
 191         fc->start = tmpll;
 192
 193         r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
 194         if (r)
 195                 goto bad;
 196
 197         r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
 198         if (r)
 199                 goto bad;
 200
 201         if (!(fc->up_interval + fc->down_interval)) {
 202                 ti->error = "Total (up + down) interval is zero";
 203                 r = -EINVAL;
 204                 goto bad;
 205         }
 206
 207         if (fc->up_interval + fc->down_interval < fc->up_interval) {
 208                 ti->error = "Interval overflow";
 209                 r = -EINVAL;
 210                 goto bad;
 211         }
 212
 213         r = parse_features(&as, fc, ti);
 214         if (r)
 215                 goto bad;
 216
 217         r = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev);
 218         if (r) {
 219                 ti->error = "Device lookup failed";
 220                 goto bad;
 221         }
 222
 223         ti->num_flush_bios = 1;
 224         ti->num_discard_bios = 1;
 225         ti->per_bio_data_size = sizeof(struct per_bio_data);
 226         ti->private = fc;
 227         return 0;
 228
 229 bad:
 230         kfree(fc);
 231         return r;
 232 }
 233
 234 static void flakey_dtr(struct dm_target *ti)
 235 {
 236         struct flakey_c *fc = ti->private;
 237
 238         dm_put_device(ti, fc->dev);
 239         kfree(fc);
 240 }
 241
 242 static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
 243 {
 244         struct flakey_c *fc = ti->private;
 245
 246         return fc->start + dm_target_offset(ti, bi_sector);
 247 }
 248
 249 static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 250 {
 251         struct flakey_c *fc = ti->private;
 252
 253         bio->bi_bdev = fc->dev->bdev;
 254         if (bio_sectors(bio))
 255                 bio->bi_iter.bi_sector =
 256                         flakey_map_sector(ti, bio->bi_iter.bi_sector);
 257 }
 258
 259 static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
 260 {
 261         unsigned bio_bytes = bio_cur_bytes(bio);
 262         char *data = bio_data(bio);
 263
 264         /*
 265          * Overwrite the Nth byte of the data returned.
 266          */
 267         if (data && bio_bytes >= fc->corrupt_bio_byte) {
 268                 data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
 269
 270                 DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
 271                         "(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
 272                         bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
 273                         (bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_rw,
 274                         (unsigned long long)bio->bi_iter.bi_sector, bio_bytes);
 275         }
 276 }
 277
 278 static int flakey_map(struct dm_target *ti, struct bio *bio)
 279 {
 280         struct flakey_c *fc = ti->private;
 281         unsigned elapsed;
 282         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 283         pb->bio_submitted = false;
 284
 285         /* Are we alive ? */
 286         elapsed = (jiffies - fc->start_time) / HZ;
 287         if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
 288                 /*
 289                  * Flag this bio as submitted while down.
 290                  */
 291                 pb->bio_submitted = true;
 292
 293                 /*
 294                  * Error reads if neither corrupt_bio_byte or drop_writes are set.
 295                  * Otherwise, flakey_end_io() will decide if the reads should be modified.
 296                  */
 297                 if (bio_data_dir(bio) == READ) {
 298                         if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags))
 299                                 return -EIO;
 300                         goto map_bio;
 301                 }
 302
 303                 /*
 304                  * Drop writes?
 305                  */
 306                 if (test_bit(DROP_WRITES, &fc->flags)) {
 307                         bio_endio(bio);
 308                         return DM_MAPIO_SUBMITTED;
 309                 }
 310
 311                 /*
 312                  * Corrupt matching writes.
 313                  */
 314                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
 315                         if (all_corrupt_bio_flags_match(bio, fc))
 316                                 corrupt_bio_data(bio, fc);
 317                         goto map_bio;
 318                 }
 319
 320                 /*
 321                  * By default, error all I/O.
 322                  */
 323                 return -EIO;
 324         }
 325
 326 map_bio:
 327         flakey_map_bio(ti, bio);
 328
 329         return DM_MAPIO_REMAPPED;
 330 }
 331
 332 static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
 333 {
 334         struct flakey_c *fc = ti->private;
 335         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 336
 337         if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) {
 338                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
 339                     all_corrupt_bio_flags_match(bio, fc)) {
 340                         /*
 341                          * Corrupt successful matching READs while in down state.
 342                          */
 343                         corrupt_bio_data(bio, fc);
 344
 345                 } else if (!test_bit(DROP_WRITES, &fc->flags)) {
 346                         /*
 347                          * Error read during the down_interval if drop_writes
 348                          * wasn't configured.
 349                          */
 350                         return -EIO;
 351                 }
 352         }
 353
 354         return error;
 355 }
 356
 357 static void flakey_status(struct dm_target *ti, status_type_t type,
 358                           unsigned status_flags, char *result, unsigned maxlen)
 359 {
 360         unsigned sz = 0;
 361         struct flakey_c *fc = ti->private;
 362         unsigned drop_writes;
 363
 364         switch (type) {
 365         case STATUSTYPE_INFO:
 366                 result[0] = '\0';
 367                 break;
 368
 369         case STATUSTYPE_TABLE:
 370                 DMEMIT("%s %llu %u %u ", fc->dev->name,
 371                        (unsigned long long)fc->start, fc->up_interval,
 372                        fc->down_interval);
 373
 374                 drop_writes = test_bit(DROP_WRITES, &fc->flags);
 375                 DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
 376
 377                 if (drop_writes)
 378                         DMEMIT("drop_writes ");
 379
 380                 if (fc->corrupt_bio_byte)
 381                         DMEMIT("corrupt_bio_byte %u %c %u %u ",
 382                                fc->corrupt_bio_byte,
 383                                (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
 384                                fc->corrupt_bio_value, fc->corrupt_bio_flags);
 385
 386                 break;
 387         }
 388 }
 389
 390 static int flakey_prepare_ioctl(struct dm_target *ti,
 391                 struct block_device **bdev, fmode_t *mode)
 392 {
 393         struct flakey_c *fc = ti->private;
 394
 395         *bdev = fc->dev->bdev;
 396
 397         /*
 398          * Only pass ioctls through if the device sizes match exactly.
 399          */
 400         if (fc->start ||
 401             ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
 402                 return 1;
 403         return 0;
 404 }
 405
 406 static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
 407 {
 408         struct flakey_c *fc = ti->private;
 409
 410         return fn(ti, fc->dev, fc->start, ti->len, data);
 411 }
 412
 413 static struct target_type flakey_target = {
 414         .name   = "flakey",
 415         .version = {1, 3, 1},
 416         .module = THIS_MODULE,
 417         .ctr    = flakey_ctr,
 418         .dtr    = flakey_dtr,
 419         .map    = flakey_map,
 420         .end_io = flakey_end_io,
 421         .status = flakey_status,
 422         .prepare_ioctl = flakey_prepare_ioctl,
 423         .iterate_devices = flakey_iterate_devices,
 424 };
 425
 426 static int __init dm_flakey_init(void)
 427 {
 428         int r = dm_register_target(&flakey_target);
 429
 430         if (r < 0)
 431                 DMERR("register failed %d", r);
 432
 433         return r;
 434 }
 435
 436 static void __exit dm_flakey_exit(void)
 437 {
 438         dm_unregister_target(&flakey_target);
 439 }
 440
 441 /* Module hooks */
 442 module_init(dm_flakey_init);
 443 module_exit(dm_flakey_exit);
 444
 445 MODULE_DESCRIPTION(DM_NAME " flakey target");
 446 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 447 MODULE_LICENSE("GPL");