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                 /*
  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                 goto bad;
 204         }
 205
 206         if (fc->up_interval + fc->down_interval < fc->up_interval) {
 207                 ti->error = "Interval overflow";
 208                 goto bad;
 209         }
 210
 211         r = parse_features(&as, fc, ti);
 212         if (r)
 213                 goto bad;
 214
 215         r = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev);
 216         if (r) {
 217                 ti->error = "Device lookup failed";
 218                 goto bad;
 219         }
 220
 221         ti->num_flush_bios = 1;
 222         ti->num_discard_bios = 1;
 223         ti->per_io_data_size = sizeof(struct per_bio_data);
 224         ti->private = fc;
 225         return 0;
 226
 227 bad:
 228         kfree(fc);
 229         return r;
 230 }
 231
 232 static void flakey_dtr(struct dm_target *ti)
 233 {
 234         struct flakey_c *fc = ti->private;
 235
 236         dm_put_device(ti, fc->dev);
 237         kfree(fc);
 238 }
 239
 240 static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
 241 {
 242         struct flakey_c *fc = ti->private;
 243
 244         return fc->start + dm_target_offset(ti, bi_sector);
 245 }
 246
 247 static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 248 {
 249         struct flakey_c *fc = ti->private;
 250
 251         bio->bi_bdev = fc->dev->bdev;
 252         if (bio_sectors(bio))
 253                 bio->bi_iter.bi_sector =
 254                         flakey_map_sector(ti, bio->bi_iter.bi_sector);
 255 }
 256
 257 static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
 258 {
 259         unsigned bio_bytes = bio_cur_bytes(bio);
 260         char *data = bio_data(bio);
 261
 262         /*
 263          * Overwrite the Nth byte of the data returned.
 264          */
 265         if (data && bio_bytes >= fc->corrupt_bio_byte) {
 266                 data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
 267
 268                 DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
 269                         "(rw=%c bi_opf=%u bi_sector=%llu cur_bytes=%u)\n",
 270                         bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
 271                         (bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_opf,
 272                         (unsigned long long)bio->bi_iter.bi_sector, bio_bytes);
 273         }
 274 }
 275
 276 static int flakey_map(struct dm_target *ti, struct bio *bio)
 277 {
 278         struct flakey_c *fc = ti->private;
 279         unsigned elapsed;
 280         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 281         pb->bio_submitted = false;
 282
 283         /* Are we alive ? */
 284         elapsed = (jiffies - fc->start_time) / HZ;
 285         if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
 286                 /*
 287                  * Flag this bio as submitted while down.
 288                  */
 289                 pb->bio_submitted = true;
 290
 291                 /*
 292                  * Error reads if neither corrupt_bio_byte or drop_writes are set.
 293                  * Otherwise, flakey_end_io() will decide if the reads should be modified.
 294                  */
 295                 if (bio_data_dir(bio) == READ) {
 296                         if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags))
 297                                 return -EIO;
 298                         goto map_bio;
 299                 }
 300
 301                 /*
 302                  * Drop writes?
 303                  */
 304                 if (test_bit(DROP_WRITES, &fc->flags)) {
 305                         bio_endio(bio);
 306                         return DM_MAPIO_SUBMITTED;
 307                 }
 308
 309                 /*
 310                  * Corrupt matching writes.
 311                  */
 312                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
 313                         if (all_corrupt_bio_flags_match(bio, fc))
 314                                 corrupt_bio_data(bio, fc);
 315                         goto map_bio;
 316                 }
 317
 318                 /*
 319                  * By default, error all I/O.
 320                  */
 321                 return -EIO;
 322         }
 323
 324 map_bio:
 325         flakey_map_bio(ti, bio);
 326
 327         return DM_MAPIO_REMAPPED;
 328 }
 329
 330 static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
 331 {
 332         struct flakey_c *fc = ti->private;
 333         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 334
 335         if (!error && pb->bio_submitted && (bio_data_dir(bio) == READ)) {
 336                 if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == READ) &&
 337                     all_corrupt_bio_flags_match(bio, fc)) {
 338                         /*
 339                          * Corrupt successful matching READs while in down state.
 340                          */
 341                         corrupt_bio_data(bio, fc);
 342
 343                 } else if (!test_bit(DROP_WRITES, &fc->flags)) {
 344                         /*
 345                          * Error read during the down_interval if drop_writes
 346                          * wasn't configured.
 347                          */
 348                         return -EIO;
 349                 }
 350         }
 351
 352         return error;
 353 }
 354
 355 static void flakey_status(struct dm_target *ti, status_type_t type,
 356                           unsigned status_flags, char *result, unsigned maxlen)
 357 {
 358         unsigned sz = 0;
 359         struct flakey_c *fc = ti->private;
 360         unsigned drop_writes;
 361
 362         switch (type) {
 363         case STATUSTYPE_INFO:
 364                 result[0] = '\0';
 365                 break;
 366
 367         case STATUSTYPE_TABLE:
 368                 DMEMIT("%s %llu %u %u ", fc->dev->name,
 369                        (unsigned long long)fc->start, fc->up_interval,
 370                        fc->down_interval);
 371
 372                 drop_writes = test_bit(DROP_WRITES, &fc->flags);
 373                 DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
 374
 375                 if (drop_writes)
 376                         DMEMIT("drop_writes ");
 377
 378                 if (fc->corrupt_bio_byte)
 379                         DMEMIT("corrupt_bio_byte %u %c %u %u ",
 380                                fc->corrupt_bio_byte,
 381                                (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
 382                                fc->corrupt_bio_value, fc->corrupt_bio_flags);
 383
 384                 break;
 385         }
 386 }
 387
 388 static int flakey_prepare_ioctl(struct dm_target *ti,
 389                 struct block_device **bdev, fmode_t *mode)
 390 {
 391         struct flakey_c *fc = ti->private;
 392
 393         *bdev = fc->dev->bdev;
 394
 395         /*
 396          * Only pass ioctls through if the device sizes match exactly.
 397          */
 398         if (fc->start ||
 399             ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
 400                 return 1;
 401         return 0;
 402 }
 403
 404 static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
 405 {
 406         struct flakey_c *fc = ti->private;
 407
 408         return fn(ti, fc->dev, fc->start, ti->len, data);
 409 }
 410
 411 static struct target_type flakey_target = {
 412         .name   = "flakey",
 413         .version = {1, 3, 1},
 414         .module = THIS_MODULE,
 415         .ctr    = flakey_ctr,
 416         .dtr    = flakey_dtr,
 417         .map    = flakey_map,
 418         .end_io = flakey_end_io,
 419         .status = flakey_status,
 420         .prepare_ioctl = flakey_prepare_ioctl,
 421         .iterate_devices = flakey_iterate_devices,
 422 };
 423
 424 static int __init dm_flakey_init(void)
 425 {
 426         int r = dm_register_target(&flakey_target);
 427
 428         if (r < 0)
 429                 DMERR("register failed %d", r);
 430
 431         return r;
 432 }
 433
 434 static void __exit dm_flakey_exit(void)
 435 {
 436         dm_unregister_target(&flakey_target);
 437 }
 438
 439 /* Module hooks */
 440 module_init(dm_flakey_init);
 441 module_exit(dm_flakey_exit);
 442
 443 MODULE_DESCRIPTION(DM_NAME " flakey target");
 444 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 445 MODULE_LICENSE("GPL");