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 typedef 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         mdk_rdev_t *rdev;
  92 } conf_t;
  93
  94 static int check_mode(conf_t *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(conf_t *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(conf_t *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 int make_request(mddev_t *mddev, struct bio *bio)
 174 {
 175         conf_t *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 0;
 186                 }
 187
 188                 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
 189                                  WRITE))
 190                         failit = 1;
 191                 if (check_mode(conf, WritePersistent)) {
 192                         add_sector(conf, bio->bi_sector, WritePersistent);
 193                         failit = 1;
 194                 }
 195                 if (check_mode(conf, WriteTransient))
 196                         failit = 1;
 197         } else {
 198                 /* read request */
 199                 if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
 200                                  READ))
 201                         failit = 1;
 202                 if (check_mode(conf, ReadTransient))
 203                         failit = 1;
 204                 if (check_mode(conf, ReadPersistent)) {
 205                         add_sector(conf, bio->bi_sector, ReadPersistent);
 206                         failit = 1;
 207                 }
 208                 if (check_mode(conf, ReadFixable)) {
 209                         add_sector(conf, bio->bi_sector, ReadFixable);
 210                         failit = 1;
 211                 }
 212         }
 213         if (failit) {
 214                 struct bio *b = bio_clone_mddev(bio, GFP_NOIO, mddev);
 215                 b->bi_bdev = conf->rdev->bdev;
 216                 b->bi_private = bio;
 217                 b->bi_end_io = faulty_fail;
 218                 generic_make_request(b);
 219                 return 0;
 220         } else {
 221                 bio->bi_bdev = conf->rdev->bdev;
 222                 return 1;
 223         }
 224 }
 225
 226 static void status(struct seq_file *seq, mddev_t *mddev)
 227 {
 228         conf_t *conf = mddev->private;
 229         int n;
 230
 231         if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
 232                 seq_printf(seq, " WriteTransient=%d(%d)",
 233                            n, conf->period[WriteTransient]);
 234
 235         if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
 236                 seq_printf(seq, " ReadTransient=%d(%d)",
 237                            n, conf->period[ReadTransient]);
 238
 239         if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
 240                 seq_printf(seq, " WritePersistent=%d(%d)",
 241                            n, conf->period[WritePersistent]);
 242
 243         if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
 244                 seq_printf(seq, " ReadPersistent=%d(%d)",
 245                            n, conf->period[ReadPersistent]);
 246
 247
 248         if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
 249                 seq_printf(seq, " ReadFixable=%d(%d)",
 250                            n, conf->period[ReadFixable]);
 251
 252         if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
 253                 seq_printf(seq, " WriteAll");
 254
 255         seq_printf(seq, " nfaults=%d", conf->nfaults);
 256 }
 257
 258
 259 static int reshape(mddev_t *mddev)
 260 {
 261         int mode = mddev->new_layout & ModeMask;
 262         int count = mddev->new_layout >> ModeShift;
 263         conf_t *conf = mddev->private;
 264
 265         if (mddev->new_layout < 0)
 266                 return 0;
 267
 268         /* new layout */
 269         if (mode == ClearFaults)
 270                 conf->nfaults = 0;
 271         else if (mode == ClearErrors) {
 272                 int i;
 273                 for (i=0 ; i < Modes ; i++) {
 274                         conf->period[i] = 0;
 275                         atomic_set(&conf->counters[i], 0);
 276                 }
 277         } else if (mode < Modes) {
 278                 conf->period[mode] = count;
 279                 if (!count) count++;
 280                 atomic_set(&conf->counters[mode], count);
 281         } else
 282                 return -EINVAL;
 283         mddev->new_layout = -1;
 284         mddev->layout = -1; /* makes sure further changes come through */
 285         return 0;
 286 }
 287
 288 static sector_t faulty_size(mddev_t *mddev, sector_t sectors, int raid_disks)
 289 {
 290         WARN_ONCE(raid_disks,
 291                   "%s does not support generic reshape\n", __func__);
 292
 293         if (sectors == 0)
 294                 return mddev->dev_sectors;
 295
 296         return sectors;
 297 }
 298
 299 static int run(mddev_t *mddev)
 300 {
 301         mdk_rdev_t *rdev;
 302         int i;
 303         conf_t *conf;
 304
 305         if (md_check_no_bitmap(mddev))
 306                 return -EINVAL;
 307
 308         conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 309         if (!conf)
 310                 return -ENOMEM;
 311
 312         for (i=0; i<Modes; i++) {
 313                 atomic_set(&conf->counters[i], 0);
 314                 conf->period[i] = 0;
 315         }
 316         conf->nfaults = 0;
 317
 318         list_for_each_entry(rdev, &mddev->disks, same_set)
 319                 conf->rdev = rdev;
 320
 321         md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 322         mddev->private = conf;
 323
 324         reshape(mddev);
 325
 326         return 0;
 327 }
 328
 329 static int stop(mddev_t *mddev)
 330 {
 331         conf_t *conf = mddev->private;
 332
 333         kfree(conf);
 334         mddev->private = NULL;
 335         return 0;
 336 }
 337
 338 static struct mdk_personality faulty_personality =
 339 {
 340         .name           = "faulty",
 341         .level          = LEVEL_FAULTY,
 342         .owner          = THIS_MODULE,
 343         .make_request   = make_request,
 344         .run            = run,
 345         .stop           = stop,
 346         .status         = status,
 347         .check_reshape  = reshape,
 348         .size           = faulty_size,
 349 };
 350
 351 static int __init raid_init(void)
 352 {
 353         return register_md_personality(&faulty_personality);
 354 }
 355
 356 static void raid_exit(void)
 357 {
 358         unregister_md_personality(&faulty_personality);
 359 }
 360
 361 module_init(raid_init);
 362 module_exit(raid_exit);
 363 MODULE_LICENSE("GPL");
 364 MODULE_DESCRIPTION("Fault injection personality for MD");
 365 MODULE_ALIAS("md-personality-10"); /* faulty */
 366 MODULE_ALIAS("md-faulty");
 367 MODULE_ALIAS("md-level--5");