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