drivers/md/faulty.c

   1 /*
   2  * faulty.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 2004 Neil Brown
   5  *
   6  * fautly-device-simulator personality for md
   7  *
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2, or (at your option)
  12  * any later version.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * (for example /usr/src/linux/COPYING); if not, write to the Free
  16  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19
  20 /*
  21  * The "faulty" personality causes some requests to fail.
  22  *
  23  * Possible failure modes are:
  24  *   reads fail "randomly" but succeed on retry
  25  *   writes fail "randomly" but succeed on retry
  26  *   reads for some address fail and then persist until a write
  27  *   reads for some address fail and then persist irrespective of write
  28  *   writes for some address fail and persist
  29  *   all writes fail
  30  *
  31  * Different modes can be active at a time, but only
  32  * one can be set at array creation.  Others can be added later.
  33  * A mode can be one-shot or recurrent with the recurrence being
  34  * once in every N requests.
  35  * The bottom 5 bits of the "layout" indicate the mode.  The
  36  * remainder indicate a period, or 0 for one-shot.
  37  *
  38  * There is an implementation limit on the number of concurrently
  39  * persisting-faulty blocks. When a new fault is requested that would
  40  * exceed the limit, it is ignored.
  41  * All current faults can be clear using a layout of "0".
  42  *
  43  * Requests are always sent to the device.  If they are to fail,
  44  * we clone the bio and insert a new b_end_io into the chain.
  45  */
  46
  47 #define WriteTransient  0
  48 #define ReadTransient   1
  49 #define WritePersistent 2
  50 #define ReadPersistent  3
  51 #define WriteAll        4 /* doesn't go to device */
  52 #define ReadFixable     5
  53 #define Modes   6
  54
  55 #define ClearErrors     31
  56 #define ClearFaults     30
  57
  58 #define AllPersist      100 /* internal use only */
  59 #define NoPersist       101
  60
  61 #define ModeMask        0x1f
  62 #define ModeShift       5
  63
  64 #define MaxFault        50
  65 #include <linux/blkdev.h>
  66 #include <linux/module.h>
  67 #include <linux/raid/md_u.h>
  68 #include <linux/slab.h>
  69 #include "md.h"
  70 #include <linux/seq_file.h>
  71
  72
  73 static void faulty_fail(struct bio *bio, int error)
  74 {
  75         struct bio *b = bio->bi_private;
  76
  77         b->bi_size = bio->bi_size;
  78         b->bi_sector = bio->bi_sector;
  79
  80         bio_put(bio);
  81
  82         bio_io_error(b);
  83 }
  84
  85 struct faulty_conf {
  86         int period[Modes];
  87         atomic_t counters[Modes];
  88         sector_t faults[MaxFault];
  89         int     modes[MaxFault];
  90         int nfaults;
  91         struct md_rdev *rdev;
  92 };
  93
  94 static int check_mode(struct faulty_conf *conf, int mode)
  95 {
  96         if (conf->period[mode] == 0 &&
  97             atomic_read(&conf->counters[mode]) <= 0)
  98                 return 0; /* no failure, no decrement */
  99
 100
 101         if (atomic_dec_and_test(&conf->counters[mode])) {
 102                 if (conf->period[mode])
 103                         atomic_set(&conf->counters[mode], conf->period[mode]);
 104                 return 1;
 105         }
 106         return 0;
 107 }
 108
 109 static int check_sector(struct faulty_conf *conf, sector_t start, sector_t end, int dir)
 110 {
 111         /* If we find a ReadFixable sector, we fix it ... */
 112         int i;
 113         for (i=0; i<conf->nfaults; i++)
 114                 if (conf->faults[i] >= start &&
 115                     conf->faults[i] < end) {
 116                         /* found it ... */
 117                         switch (conf->modes[i] * 2 + dir) {
 118                         case WritePersistent*2+WRITE: return 1;
 119                         case ReadPersistent*2+READ: return 1;
 120                         case ReadFixable*2+READ: return 1;
 121                         case ReadFixable*2+WRITE:
 122                                 conf->modes[i] = NoPersist;
 123                                 return 0;
 124                         case AllPersist*2+READ:
 125                         case AllPersist*2+WRITE: return 1;
 126                         default:
 127                                 return 0;
 128                         }
 129                 }
 130         return 0;
 131 }
 132
 133 static void add_sector(struct faulty_conf *conf, sector_t start, int mode)
 134 {
 135         int i;
 136         int n = conf->nfaults;
 137         for (i=0; i<conf->nfaults; i++)
 138                 if (conf->faults[i] == start) {
 139                         switch(mode) {
 140                         case NoPersist: conf->modes[i] = mode; return;
 141                         case WritePersistent:
 142                                 if (conf->modes[i] == ReadPersistent ||
 143                                     conf->modes[i] == ReadFixable)
 144                                         conf->modes[i] = AllPersist;
 145                                 else
 146                                         conf->modes[i] = WritePersistent;
 147                                 return;
 148                         case ReadPersistent:
 149                                 if (conf->modes[i] == WritePersistent)
 150                                         conf->modes[i] = AllPersist;
 151                                 else
 152                                         conf->modes[i] = ReadPersistent;
 153                                 return;
 154                         case ReadFixable:
 155                                 if (conf->modes[i] == WritePersistent ||
 156                                     conf->modes[i] == ReadPersistent)
 157                                         conf->modes[i] = AllPersist;
 158                                 else
 159                                         conf->modes[i] = ReadFixable;
 160                                 return;
 161                         }
 162                 } else if (conf->modes[i] == NoPersist)
 163                         n = i;
 164
 165         if (n >= MaxFault)
 166                 return;
 167         conf->faults[n] = start;
 168         conf->modes[n] = mode;
 169         if (conf->nfaults == n)
 170                 conf->nfaults = n+1;
 171 }
 172
 173 static void make_request(struct mddev *mddev, struct bio *bio)
 174 {
 175         struct faulty_conf *conf = mddev->private;
 176         int failit = 0;
 177
 178         if (bio_data_dir(bio) == WRITE) {
 179                 /* write request */
 180                 if (atomic_read(&conf->counters[WriteAll])) {
 181                         /* special case - don't decrement, don't generic_make_request,
 182                          * just fail immediately
 183                          */
 184                         bio_endio(bio, -EIO);
 185                         return;
 186                 }
 187
 188                 if (check_sector(conf, bio->bi_sector, bio_end_sector(bio), WRITE))
 189                         failit = 1;
 190                 if (check_mode(conf, WritePersistent)) {
 191                         add_sector(conf, bio->bi_sector, WritePersistent);
 192                         failit = 1;
 193                 }
 194                 if (check_mode(conf, WriteTransient))
 195                         failit = 1;
 196         } else {
 197                 /* read request */
 198                 if (check_sector(conf, bio->bi_sector, bio_end_sector(bio), READ))
 199                         failit = 1;
 200                 if (check_mode(conf, ReadTransient))
 201                         failit = 1;
 202                 if (check_mode(conf, ReadPersistent)) {
 203                         add_sector(conf, bio->bi_sector, ReadPersistent);
 204                         failit = 1;
 205                 }
 206                 if (check_mode(conf, ReadFixable)) {
 207                         add_sector(conf, bio->bi_sector, ReadFixable);
 208                         failit = 1;
 209                 }
 210         }
 211         if (failit) {
 212                 struct bio *b = bio_clone_mddev(bio, GFP_NOIO, mddev);
 213
 214                 b->bi_bdev = conf->rdev->bdev;
 215                 b->bi_private = bio;
 216                 b->bi_end_io = faulty_fail;
 217                 bio = b;
 218         } else
 219                 bio->bi_bdev = conf->rdev->bdev;
 220
 221         generic_make_request(bio);
 222 }
 223
 224 static void status(struct seq_file *seq, struct mddev *mddev)
 225 {
 226         struct faulty_conf *conf = mddev->private;
 227         int n;
 228
 229         if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
 230                 seq_printf(seq, " WriteTransient=%d(%d)",
 231                            n, conf->period[WriteTransient]);
 232
 233         if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
 234                 seq_printf(seq, " ReadTransient=%d(%d)",
 235                            n, conf->period[ReadTransient]);
 236
 237         if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
 238                 seq_printf(seq, " WritePersistent=%d(%d)",
 239                            n, conf->period[WritePersistent]);
 240
 241         if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
 242                 seq_printf(seq, " ReadPersistent=%d(%d)",
 243                            n, conf->period[ReadPersistent]);
 244
 245
 246         if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
 247                 seq_printf(seq, " ReadFixable=%d(%d)",
 248                            n, conf->period[ReadFixable]);
 249
 250         if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
 251                 seq_printf(seq, " WriteAll");
 252
 253         seq_printf(seq, " nfaults=%d", conf->nfaults);
 254 }
 255
 256
 257 static int reshape(struct mddev *mddev)
 258 {
 259         int mode = mddev->new_layout & ModeMask;
 260         int count = mddev->new_layout >> ModeShift;
 261         struct faulty_conf *conf = mddev->private;
 262
 263         if (mddev->new_layout < 0)
 264                 return 0;
 265
 266         /* new layout */
 267         if (mode == ClearFaults)
 268                 conf->nfaults = 0;
 269         else if (mode == ClearErrors) {
 270                 int i;
 271                 for (i=0 ; i < Modes ; i++) {
 272                         conf->period[i] = 0;
 273                         atomic_set(&conf->counters[i], 0);
 274                 }
 275         } else if (mode < Modes) {
 276                 conf->period[mode] = count;
 277                 if (!count) count++;
 278                 atomic_set(&conf->counters[mode], count);
 279         } else
 280                 return -EINVAL;
 281         mddev->new_layout = -1;
 282         mddev->layout = -1; /* makes sure further changes come through */
 283         return 0;
 284 }
 285
 286 static sector_t faulty_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 287 {
 288         WARN_ONCE(raid_disks,
 289                   "%s does not support generic reshape\n", __func__);
 290
 291         if (sectors == 0)
 292                 return mddev->dev_sectors;
 293
 294         return sectors;
 295 }
 296
 297 static int run(struct mddev *mddev)
 298 {
 299         struct md_rdev *rdev;
 300         int i;
 301         struct faulty_conf *conf;
 302
 303         if (md_check_no_bitmap(mddev))
 304                 return -EINVAL;
 305
 306         conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 307         if (!conf)
 308                 return -ENOMEM;
 309
 310         for (i=0; i<Modes; i++) {
 311                 atomic_set(&conf->counters[i], 0);
 312                 conf->period[i] = 0;
 313         }
 314         conf->nfaults = 0;
 315
 316         rdev_for_each(rdev, mddev) {
 317                 conf->rdev = rdev;
 318                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 319                                   rdev->data_offset << 9);
 320         }
 321
 322         md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 323         mddev->private = conf;
 324
 325         reshape(mddev);
 326
 327         return 0;
 328 }
 329
 330 static int stop(struct mddev *mddev)
 331 {
 332         struct faulty_conf *conf = mddev->private;
 333
 334         kfree(conf);
 335         mddev->private = NULL;
 336         return 0;
 337 }
 338
 339 static struct md_personality faulty_personality =
 340 {
 341         .name           = "faulty",
 342         .level          = LEVEL_FAULTY,
 343         .owner          = THIS_MODULE,
 344         .make_request   = make_request,
 345         .run            = run,
 346         .stop           = stop,
 347         .status         = status,
 348         .check_reshape  = reshape,
 349         .size           = faulty_size,
 350 };
 351
 352 static int __init raid_init(void)
 353 {
 354         return register_md_personality(&faulty_personality);
 355 }
 356
 357 static void raid_exit(void)
 358 {
 359         unregister_md_personality(&faulty_personality);
 360 }
 361
 362 module_init(raid_init);
 363 module_exit(raid_exit);
 364 MODULE_LICENSE("GPL");
 365 MODULE_DESCRIPTION("Fault injection personality for MD");
 366 MODULE_ALIAS("md-personality-10"); /* faulty */
 367 MODULE_ALIAS("md-faulty");
 368 MODULE_ALIAS("md-level--5");