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
  42struct per_bio_data {
  43        bool bio_submitted;
  44};
  45
  46static 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 */
 155static 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 linear context";
 180                return -ENOMEM;
 181        }
 182        fc->start_time = jiffies;
 183
 184        devname = dm_shift_arg(&as);
 185
 186        if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1) {
 187                ti->error = "Invalid device sector";
 188                goto bad;
 189        }
 190        fc->start = tmpll;
 191
 192        r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
 193        if (r)
 194                goto bad;
 195
 196        r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
 197        if (r)
 198                goto bad;
 199
 200        if (!(fc->up_interval + fc->down_interval)) {
 201                ti->error = "Total (up + down) interval is zero";
 202                goto bad;
 203        }
 204
 205        if (fc->up_interval + fc->down_interval < fc->up_interval) {
 206                ti->error = "Interval overflow";
 207                goto bad;
 208        }
 209
 210        r = parse_features(&as, fc, ti);
 211        if (r)
 212                goto bad;
 213
 214        if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
 215                ti->error = "Device lookup failed";
 216                goto bad;
 217        }
 218
 219        ti->num_flush_bios = 1;
 220        ti->num_discard_bios = 1;
 221        ti->per_bio_data_size = sizeof(struct per_bio_data);
 222        ti->private = fc;
 223        return 0;
 224
 225bad:
 226        kfree(fc);
 227        return -EINVAL;
 228}
 229
 230static void flakey_dtr(struct dm_target *ti)
 231{
 232        struct flakey_c *fc = ti->private;
 233
 234        dm_put_device(ti, fc->dev);
 235        kfree(fc);
 236}
 237
 238static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
 239{
 240        struct flakey_c *fc = ti->private;
 241
 242        return fc->start + dm_target_offset(ti, bi_sector);
 243}
 244
 245static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 246{
 247        struct flakey_c *fc = ti->private;
 248
 249        bio->bi_bdev = fc->dev->bdev;
 250        if (bio_sectors(bio))
 251                bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
 252}
 253
 254static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
 255{
 256        unsigned bio_bytes = bio_cur_bytes(bio);
 257        char *data = bio_data(bio);
 258
 259        /*
 260         * Overwrite the Nth byte of the data returned.
 261         */
 262        if (data && bio_bytes >= fc->corrupt_bio_byte) {
 263                data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
 264
 265                DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
 266                        "(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
 267                        bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
 268                        (bio_data_dir(bio) == WRITE) ? 'w' : 'r',
 269                        bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
 270        }
 271}
 272
 273static int flakey_map(struct dm_target *ti, struct bio *bio)
 274{
 275        struct flakey_c *fc = ti->private;
 276        unsigned elapsed;
 277        struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 278        pb->bio_submitted = false;
 279
 280        /* Are we alive ? */
 281        elapsed = (jiffies - fc->start_time) / HZ;
 282        if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
 283                /*
 284                 * Flag this bio as submitted while down.
 285                 */
 286                pb->bio_submitted = true;
 287
 288                /*
 289                 * Map reads as normal.
 290                 */
 291                if (bio_data_dir(bio) == READ)
 292                        goto map_bio;
 293
 294                /*
 295                 * Drop writes?
 296                 */
 297                if (test_bit(DROP_WRITES, &fc->flags)) {
 298                        bio_endio(bio, 0);
 299                        return DM_MAPIO_SUBMITTED;
 300                }
 301
 302                /*
 303                 * Corrupt matching writes.
 304                 */
 305                if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
 306                        if (all_corrupt_bio_flags_match(bio, fc))
 307                                corrupt_bio_data(bio, fc);
 308                        goto map_bio;
 309                }
 310
 311                /*
 312                 * By default, error all I/O.
 313                 */
 314                return -EIO;
 315        }
 316
 317map_bio:
 318        flakey_map_bio(ti, bio);
 319
 320        return DM_MAPIO_REMAPPED;
 321}
 322
 323static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
 324{
 325        struct flakey_c *fc = ti->private;
 326        struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 327
 328        /*
 329         * Corrupt successful READs while in down state.
 330         * If flags were specified, only corrupt those that match.
 331         */
 332        if (fc->corrupt_bio_byte && !error && pb->bio_submitted &&
 333            (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
 334            all_corrupt_bio_flags_match(bio, fc))
 335                corrupt_bio_data(bio, fc);
 336
 337        return error;
 338}
 339
 340static void flakey_status(struct dm_target *ti, status_type_t type,
 341                          unsigned status_flags, char *result, unsigned maxlen)
 342{
 343        unsigned sz = 0;
 344        struct flakey_c *fc = ti->private;
 345        unsigned drop_writes;
 346
 347        switch (type) {
 348        case STATUSTYPE_INFO:
 349                result[0] = '\0';
 350                break;
 351
 352        case STATUSTYPE_TABLE:
 353                DMEMIT("%s %llu %u %u ", fc->dev->name,
 354                       (unsigned long long)fc->start, fc->up_interval,
 355                       fc->down_interval);
 356
 357                drop_writes = test_bit(DROP_WRITES, &fc->flags);
 358                DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
 359
 360                if (drop_writes)
 361                        DMEMIT("drop_writes ");
 362
 363                if (fc->corrupt_bio_byte)
 364                        DMEMIT("corrupt_bio_byte %u %c %u %u ",
 365                               fc->corrupt_bio_byte,
 366                               (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
 367                               fc->corrupt_bio_value, fc->corrupt_bio_flags);
 368
 369                break;
 370        }
 371}
 372
 373static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
 374{
 375        struct flakey_c *fc = ti->private;
 376        struct dm_dev *dev = fc->dev;
 377        int r = 0;
 378
 379        /*
 380         * Only pass ioctls through if the device sizes match exactly.
 381         */
 382        if (fc->start ||
 383            ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 384                r = scsi_verify_blk_ioctl(NULL, cmd);
 385
 386        return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
 387}
 388
 389static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 390                        struct bio_vec *biovec, int max_size)
 391{
 392        struct flakey_c *fc = ti->private;
 393        struct request_queue *q = bdev_get_queue(fc->dev->bdev);
 394
 395        if (!q->merge_bvec_fn)
 396                return max_size;
 397
 398        bvm->bi_bdev = fc->dev->bdev;
 399        bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
 400
 401        return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 402}
 403
 404static 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
 411static 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        .ioctl  = flakey_ioctl,
 421        .merge  = flakey_merge,
 422        .iterate_devices = flakey_iterate_devices,
 423};
 424
 425static int __init dm_flakey_init(void)
 426{
 427        int r = dm_register_target(&flakey_target);
 428
 429        if (r < 0)
 430                DMERR("register failed %d", r);
 431
 432        return r;
 433}
 434
 435static void __exit dm_flakey_exit(void)
 436{
 437        dm_unregister_target(&flakey_target);
 438}
 439
 440/* Module hooks */
 441module_init(dm_flakey_init);
 442module_exit(dm_flakey_exit);
 443
 444MODULE_DESCRIPTION(DM_NAME " flakey target");
 445MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 446MODULE_LICENSE("GPL");
 447
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