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                         struct batch_complete *batch)
  75 {
  76         struct bio *b = bio->bi_private;
  77
  78         b->bi_size = bio->bi_size;
  79         b->bi_sector = bio->bi_sector;
  80
  81         bio_put(bio);
  82
  83         bio_io_error(b);
  84 }
  85
  86 struct faulty_conf {
  87         int period[Modes];
  88         atomic_t counters[Modes];
  89         sector_t faults[MaxFault];
  90         int     modes[MaxFault];
  91         int nfaults;
  92         struct md_rdev *rdev;
  93 };
  94
  95 static int check_mode(struct faulty_conf *conf, int mode)
  96 {
  97         if (conf->period[mode] == 0 &&
  98             atomic_read(&conf->counters[mode]) <= 0)
  99                 return 0; /* no failure, no decrement */
 100
 101
 102         if (atomic_dec_and_test(&conf->counters[mode])) {
 103                 if (conf->period[mode])
 104                         atomic_set(&conf->counters[mode], conf->period[mode]);
 105                 return 1;
 106         }
 107         return 0;
 108 }
 109
 110 static int check_sector(struct faulty_conf *conf, sector_t start, sector_t end, int dir)
 111 {
 112         /* If we find a ReadFixable sector, we fix it ... */
 113         int i;
 114         for (i=0; i<conf->nfaults; i++)
 115                 if (conf->faults[i] >= start &&
 116                     conf->faults[i] < end) {
 117                         /* found it ... */
 118                         switch (conf->modes[i] * 2 + dir) {
 119                         case WritePersistent*2+WRITE: return 1;
 120                         case ReadPersistent*2+READ: return 1;
 121                         case ReadFixable*2+READ: return 1;
 122                         case ReadFixable*2+WRITE:
 123                                 conf->modes[i] = NoPersist;
 124                                 return 0;
 125                         case AllPersist*2+READ:
 126                         case AllPersist*2+WRITE: return 1;
 127                         default:
 128                                 return 0;
 129                         }
 130                 }
 131         return 0;
 132 }
 133
 134 static void add_sector(struct faulty_conf *conf, sector_t start, int mode)
 135 {
 136         int i;
 137         int n = conf->nfaults;
 138         for (i=0; i<conf->nfaults; i++)
 139                 if (conf->faults[i] == start) {
 140                         switch(mode) {
 141                         case NoPersist: conf->modes[i] = mode; return;
 142                         case WritePersistent:
 143                                 if (conf->modes[i] == ReadPersistent ||
 144                                     conf->modes[i] == ReadFixable)
 145                                         conf->modes[i] = AllPersist;
 146                                 else
 147                                         conf->modes[i] = WritePersistent;
 148                                 return;
 149                         case ReadPersistent:
 150                                 if (conf->modes[i] == WritePersistent)
 151                                         conf->modes[i] = AllPersist;
 152                                 else
 153                                         conf->modes[i] = ReadPersistent;
 154                                 return;
 155                         case ReadFixable:
 156                                 if (conf->modes[i] == WritePersistent ||
 157                                     conf->modes[i] == ReadPersistent)
 158                                         conf->modes[i] = AllPersist;
 159                                 else
 160                                         conf->modes[i] = ReadFixable;
 161                                 return;
 162                         }
 163                 } else if (conf->modes[i] == NoPersist)
 164                         n = i;
 165
 166         if (n >= MaxFault)
 167                 return;
 168         conf->faults[n] = start;
 169         conf->modes[n] = mode;
 170         if (conf->nfaults == n)
 171                 conf->nfaults = n+1;
 172 }
 173
 174 static void make_request(struct mddev *mddev, struct bio *bio)
 175 {
 176         struct faulty_conf *conf = mddev->private;
 177         int failit = 0;
 178
 179         if (bio_data_dir(bio) == WRITE) {
 180                 /* write request */
 181                 if (atomic_read(&conf->counters[WriteAll])) {
 182                         /* special case - don't decrement, don't generic_make_request,
 183                          * just fail immediately
 184                          */
 185                         bio_endio(bio, -EIO);
 186                         return;
 187                 }
 188
 189                 if (check_sector(conf, bio->bi_sector, bio_end_sector(bio), 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_end_sector(bio), READ))
 200                         failit = 1;
 201                 if (check_mode(conf, ReadTransient))
 202                         failit = 1;
 203                 if (check_mode(conf, ReadPersistent)) {
 204                         add_sector(conf, bio->bi_sector, ReadPersistent);
 205                         failit = 1;
 206                 }
 207                 if (check_mode(conf, ReadFixable)) {
 208                         add_sector(conf, bio->bi_sector, ReadFixable);
 209                         failit = 1;
 210                 }
 211         }
 212         if (failit) {
 213                 struct bio *b = bio_clone_mddev(bio, GFP_NOIO, mddev);
 214
 215                 b->bi_bdev = conf->rdev->bdev;
 216                 b->bi_private = bio;
 217                 b->bi_end_io = faulty_fail;
 218                 bio = b;
 219         } else
 220                 bio->bi_bdev = conf->rdev->bdev;
 221
 222         generic_make_request(bio);
 223 }
 224
 225 static void status(struct seq_file *seq, struct mddev *mddev)
 226 {
 227         struct faulty_conf *conf = mddev->private;
 228         int n;
 229
 230         if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
 231                 seq_printf(seq, " WriteTransient=%d(%d)",
 232                            n, conf->period[WriteTransient]);
 233
 234         if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
 235                 seq_printf(seq, " ReadTransient=%d(%d)",
 236                            n, conf->period[ReadTransient]);
 237
 238         if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
 239                 seq_printf(seq, " WritePersistent=%d(%d)",
 240                            n, conf->period[WritePersistent]);
 241
 242         if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
 243                 seq_printf(seq, " ReadPersistent=%d(%d)",
 244                            n, conf->period[ReadPersistent]);
 245
 246
 247         if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
 248                 seq_printf(seq, " ReadFixable=%d(%d)",
 249                            n, conf->period[ReadFixable]);
 250
 251         if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
 252                 seq_printf(seq, " WriteAll");
 253
 254         seq_printf(seq, " nfaults=%d", conf->nfaults);
 255 }
 256
 257
 258 static int reshape(struct mddev *mddev)
 259 {
 260         int mode = mddev->new_layout & ModeMask;
 261         int count = mddev->new_layout >> ModeShift;
 262         struct faulty_conf *conf = mddev->private;
 263
 264         if (mddev->new_layout < 0)
 265                 return 0;
 266
 267         /* new layout */
 268         if (mode == ClearFaults)
 269                 conf->nfaults = 0;
 270         else if (mode == ClearErrors) {
 271                 int i;
 272                 for (i=0 ; i < Modes ; i++) {
 273                         conf->period[i] = 0;
 274                         atomic_set(&conf->counters[i], 0);
 275                 }
 276         } else if (mode < Modes) {
 277                 conf->period[mode] = count;
 278                 if (!count) count++;
 279                 atomic_set(&conf->counters[mode], count);
 280         } else
 281                 return -EINVAL;
 282         mddev->new_layout = -1;
 283         mddev->layout = -1; /* makes sure further changes come through */
 284         return 0;
 285 }
 286
 287 static sector_t faulty_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 288 {
 289         WARN_ONCE(raid_disks,
 290                   "%s does not support generic reshape\n", __func__);
 291
 292         if (sectors == 0)
 293                 return mddev->dev_sectors;
 294
 295         return sectors;
 296 }
 297
 298 static int run(struct mddev *mddev)
 299 {
 300         struct md_rdev *rdev;
 301         int i;
 302         struct faulty_conf *conf;
 303
 304         if (md_check_no_bitmap(mddev))
 305                 return -EINVAL;
 306
 307         conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 308         if (!conf)
 309                 return -ENOMEM;
 310
 311         for (i=0; i<Modes; i++) {
 312                 atomic_set(&conf->counters[i], 0);
 313                 conf->period[i] = 0;
 314         }
 315         conf->nfaults = 0;
 316
 317         rdev_for_each(rdev, mddev) {
 318                 conf->rdev = rdev;
 319                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 320                                   rdev->data_offset << 9);
 321         }
 322
 323         md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 324         mddev->private = conf;
 325
 326         reshape(mddev);
 327
 328         return 0;
 329 }
 330
 331 static int stop(struct mddev *mddev)
 332 {
 333         struct faulty_conf *conf = mddev->private;
 334
 335         kfree(conf);
 336         mddev->private = NULL;
 337         return 0;
 338 }
 339
 340 static struct md_personality faulty_personality =
 341 {
 342         .name           = "faulty",
 343         .level          = LEVEL_FAULTY,
 344         .owner          = THIS_MODULE,
 345         .make_request   = make_request,
 346         .run            = run,
 347         .stop           = stop,
 348         .status         = status,
 349         .check_reshape  = reshape,
 350         .size           = faulty_size,
 351 };
 352
 353 static int __init raid_init(void)
 354 {
 355         return register_md_personality(&faulty_personality);
 356 }
 357
 358 static void raid_exit(void)
 359 {
 360         unregister_md_personality(&faulty_personality);
 361 }
 362
 363 module_init(raid_init);
 364 module_exit(raid_exit);
 365 MODULE_LICENSE("GPL");
 366 MODULE_DESCRIPTION("Fault injection personality for MD");
 367 MODULE_ALIAS("md-personality-10"); /* faulty */
 368 MODULE_ALIAS("md-faulty");
 369 MODULE_ALIAS("md-level--5");