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_opf & (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                 if (!arg_name) {
  73                         ti->error = "Insufficient feature arguments";
  74                         return -EINVAL;
  75                 }
  76
  77                 /*
  78                  * drop_writes
  79                  */
  80                 if (!strcasecmp(arg_name, "drop_writes")) {
  81                         if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
  82                                 ti->error = "Feature drop_writes duplicated";
  83                                 return -EINVAL;
  84                         }
  85
  86                         continue;
  87                 }
  88
  89                 /*
  90                  * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
  91                  */
  92                 if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
  93                         if (!argc) {
  94                                 ti->error = "Feature corrupt_bio_byte requires parameters";
  95                                 return -EINVAL;
  96                         }
  97
  98                         r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
  99                         if (r)
 100                                 return r;
 101                         argc--;
 102
 103                         /*
 104                          * Direction r or w?
 105                          */
 106                         arg_name = dm_shift_arg(as);
 107                         if (!strcasecmp(arg_name, "w"))
 108                                 fc->corrupt_bio_rw = WRITE;
 109                         else if (!strcasecmp(arg_name, "r"))
 110                                 fc->corrupt_bio_rw = READ;
 111                         else {
 112                                 ti->error = "Invalid corrupt bio direction (r or w)";
 113                                 return -EINVAL;
 114                         }
 115                         argc--;
 116
 117                         /*
 118                          * Value of byte (0-255) to write in place of correct one.
 119                          */
 120                         r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
 121                         if (r)
 122                                 return r;
 123                         argc--;
 124
 125                         /*
 126                          * Only corrupt bios with these flags set.
 127                          */
 128                         r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
 129                         if (r)
 130                                 return r;
 131                         argc--;
 132
 133                         continue;
 134                 }
 135
 136                 ti->error = "Unrecognised flakey feature requested";
 137                 return -EINVAL;
 138         }
 139
 140         if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
 141                 ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
 142                 return -EINVAL;
 143         }
 144
 145         return 0;
 146 }
 147
 148 /*
 149  * Construct a flakey mapping:
 150  * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
 151  *
 152  *   Feature args:
 153  *     [drop_writes]
 154  *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
 155  *
 156  *   Nth_byte starts from 1 for the first byte.
 157  *   Direction is r for READ or w for WRITE.
 158  *   bio_flags is ignored if 0.
 159  */
 160 static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 161 {
 162         static struct dm_arg _args[] = {
 163                 {0, UINT_MAX, "Invalid up interval"},
 164                 {0, UINT_MAX, "Invalid down interval"},
 165         };
 166
 167         int r;
 168         struct flakey_c *fc;
 169         unsigned long long tmpll;
 170         struct dm_arg_set as;
 171         const char *devname;
 172         char dummy;
 173
 174         as.argc = argc;
 175         as.argv = argv;
 176
 177         if (argc < 4) {
 178                 ti->error = "Invalid argument count";
 179                 return -EINVAL;
 180         }
 181
 182         fc = kzalloc(sizeof(*fc), GFP_KERNEL);
 183         if (!fc) {
 184                 ti->error = "Cannot allocate context";
 185                 return -ENOMEM;
 186         }
 187         fc->start_time = jiffies;
 188
 189         devname = dm_shift_arg(&as);
 190
 191         r = -EINVAL;
 192         if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1) {
 193                 ti->error = "Invalid device sector";
 194                 goto bad;
 195         }
 196         fc->start = tmpll;
 197
 198         r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
 199         if (r)
 200                 goto bad;
 201
 202         r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
 203         if (r)
 204                 goto bad;
 205
 206         if (!(fc->up_interval + fc->down_interval)) {
 207                 ti->error = "Total (up + down) interval is zero";
 208                 r = -EINVAL;
 209                 goto bad;
 210         }
 211
 212         if (fc->up_interval + fc->down_interval < fc->up_interval) {
 213                 ti->error = "Interval overflow";
 214                 r = -EINVAL;
 215                 goto bad;
 216         }
 217
 218         r = parse_features(&as, fc, ti);
 219         if (r)
 220                 goto bad;
 221
 222         r = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev);
 223         if (r) {
 224                 ti->error = "Device lookup failed";
 225                 goto bad;
 226         }
 227
 228         ti->num_flush_bios = 1;
 229         ti->num_discard_bios = 1;
 230         ti->per_io_data_size = sizeof(struct per_bio_data);
 231         ti->private = fc;
 232         return 0;
 233
 234 bad:
 235         kfree(fc);
 236         return r;
 237 }
 238
 239 static void flakey_dtr(struct dm_target *ti)
 240 {
 241         struct flakey_c *fc = ti->private;
 242
 243         dm_put_device(ti, fc->dev);
 244         kfree(fc);
 245 }
 246
 247 static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
 248 {
 249         struct flakey_c *fc = ti->private;
 250
 251         return fc->start + dm_target_offset(ti, bi_sector);
 252 }
 253
 254 static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 255 {
 256         struct flakey_c *fc = ti->private;
 257
 258         bio->bi_bdev = fc->dev->bdev;
 259         if (bio_sectors(bio))
 260                 bio->bi_iter.bi_sector =
 261                         flakey_map_sector(ti, bio->bi_iter.bi_sector);
 262 }
 263
 264 static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
 265 {
 266         unsigned int corrupt_bio_byte = fc->corrupt_bio_byte - 1;
 267
 268         struct bvec_iter iter;
 269         struct bio_vec bvec;
 270
 271         if (!bio_has_data(bio))
 272                 return;
 273
 274         /*
 275          * Overwrite the Nth byte of the bio's data, on whichever page
 276          * it falls.
 277          */
 278         bio_for_each_segment(bvec, bio, iter) {
 279                 if (bio_iter_len(bio, iter) > corrupt_bio_byte) {
 280                         char *segment = (page_address(bio_iter_page(bio, iter))
 281                                          + bio_iter_offset(bio, iter));
 282                         segment[corrupt_bio_byte] = fc->corrupt_bio_value;
 283                         DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
 284                                 "(rw=%c bi_opf=%u bi_sector=%llu size=%u)\n",
 285                                 bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
 286                                 (bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_opf,
 287                                 (unsigned long long)bio->bi_iter.bi_sector, bio->bi_iter.bi_size);
 288                         break;
 289                 }
 290                 corrupt_bio_byte -= bio_iter_len(bio, iter);
 291         }
 292 }
 293
 294 static int flakey_map(struct dm_target *ti, struct bio *bio)
 295 {
 296         struct flakey_c *fc = ti->private;
 297         unsigned elapsed;
 298         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 299         pb->bio_submitted = false;
 300
 301         /* Are we alive ? */
 302         elapsed = (jiffies - fc->start_time) / HZ;
 303         if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
 304                 /*
 305                  * Flag this bio as submitted while down.
 306                  */
 307                 pb->bio_submitted = true;
 308
 309                 /*
 310                  * Error reads if neither corrupt_bio_byte or drop_writes are set.
 311                  * Otherwise, flakey_end_io() will decide if the reads should be modified.
 312                  */
 313                 if (bio_data_dir(bio) == READ) {
 314                         if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags))
 315                                 return -EIO;
 316                         goto map_bio;
 317                 }
 318
 319                 /*
 320                  * Drop writes?
 321                  */
 322                 if (test_bit(DROP_WRITES, &fc->flags)) {
 323                         bio_endio(bio);
 324                         return DM_MAPIO_SUBMITTED;
 325                 }
 326
 327                 /*
 328                  * Corrupt matching writes.
 329                  */
 330                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
 331                         if (all_corrupt_bio_flags_match(bio, fc))
 332                                 corrupt_bio_data(bio, fc);
 333                         goto map_bio;
 334                 }
 335
 336                 /*
 337                  * By default, error all I/O.
 338                  */
 339                 return -EIO;
 340         }
 341
 342 map_bio:
 343         flakey_map_bio(ti, bio);
 344
 345         return DM_MAPIO_REMAPPED;
 346 }
 347
 348 static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
 349 {
 350         struct flakey_c *fc = ti->private;
 351         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 352
 353         if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) {
 354                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
 355                     all_corrupt_bio_flags_match(bio, fc)) {
 356                         /*
 357                          * Corrupt successful matching READs while in down state.
 358                          */
 359                         corrupt_bio_data(bio, fc);
 360
 361                 } else if (!test_bit(DROP_WRITES, &fc->flags)) {
 362                         /*
 363                          * Error read during the down_interval if drop_writes
 364                          * wasn't configured.
 365                          */
 366                         return -EIO;
 367                 }
 368         }
 369
 370         return error;
 371 }
 372
 373 static void flakey_status(struct dm_target *ti, status_type_t type,
 374                           unsigned status_flags, char *result, unsigned maxlen)
 375 {
 376         unsigned sz = 0;
 377         struct flakey_c *fc = ti->private;
 378         unsigned drop_writes;
 379
 380         switch (type) {
 381         case STATUSTYPE_INFO:
 382                 result[0] = '\0';
 383                 break;
 384
 385         case STATUSTYPE_TABLE:
 386                 DMEMIT("%s %llu %u %u ", fc->dev->name,
 387                        (unsigned long long)fc->start, fc->up_interval,
 388                        fc->down_interval);
 389
 390                 drop_writes = test_bit(DROP_WRITES, &fc->flags);
 391                 DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
 392
 393                 if (drop_writes)
 394                         DMEMIT("drop_writes ");
 395
 396                 if (fc->corrupt_bio_byte)
 397                         DMEMIT("corrupt_bio_byte %u %c %u %u ",
 398                                fc->corrupt_bio_byte,
 399                                (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
 400                                fc->corrupt_bio_value, fc->corrupt_bio_flags);
 401
 402                 break;
 403         }
 404 }
 405
 406 static int flakey_prepare_ioctl(struct dm_target *ti,
 407                 struct block_device **bdev, fmode_t *mode)
 408 {
 409         struct flakey_c *fc = ti->private;
 410
 411         *bdev = fc->dev->bdev;
 412
 413         /*
 414          * Only pass ioctls through if the device sizes match exactly.
 415          */
 416         if (fc->start ||
 417             ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
 418                 return 1;
 419         return 0;
 420 }
 421
 422 static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
 423 {
 424         struct flakey_c *fc = ti->private;
 425
 426         return fn(ti, fc->dev, fc->start, ti->len, data);
 427 }
 428
 429 static struct target_type flakey_target = {
 430         .name   = "flakey",
 431         .version = {1, 3, 1},
 432         .module = THIS_MODULE,
 433         .ctr    = flakey_ctr,
 434         .dtr    = flakey_dtr,
 435         .map    = flakey_map,
 436         .end_io = flakey_end_io,
 437         .status = flakey_status,
 438         .prepare_ioctl = flakey_prepare_ioctl,
 439         .iterate_devices = flakey_iterate_devices,
 440 };
 441
 442 static int __init dm_flakey_init(void)
 443 {
 444         int r = dm_register_target(&flakey_target);
 445
 446         if (r < 0)
 447                 DMERR("register failed %d", r);
 448
 449         return r;
 450 }
 451
 452 static void __exit dm_flakey_exit(void)
 453 {
 454         dm_unregister_target(&flakey_target);
 455 }
 456
 457 /* Module hooks */
 458 module_init(dm_flakey_init);
 459 module_exit(dm_flakey_exit);
 460
 461 MODULE_DESCRIPTION(DM_NAME " flakey target");
 462 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 463 MODULE_LICENSE("GPL");