linux/drivers/md/faulty.c
<<
>>
Prefs
   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
  73static 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
  85struct 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
  94static 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
 109static 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
 133static 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
 173static 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->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
 216                b->bi_bdev = conf->rdev->bdev;
 217                b->bi_private = bio;
 218                b->bi_end_io = faulty_fail;
 219                bio = b;
 220        } else
 221                bio->bi_bdev = conf->rdev->bdev;
 222
 223        generic_make_request(bio);
 224}
 225
 226static void status(struct seq_file *seq, struct mddev *mddev)
 227{
 228        struct faulty_conf *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
 259static int reshape(struct mddev *mddev)
 260{
 261        int mode = mddev->new_layout & ModeMask;
 262        int count = mddev->new_layout >> ModeShift;
 263        struct faulty_conf *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
 288static sector_t faulty_size(struct mddev *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
 299static int run(struct mddev *mddev)
 300{
 301        struct md_rdev *rdev;
 302        int i;
 303        struct faulty_conf *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        rdev_for_each(rdev, mddev) {
 319                conf->rdev = rdev;
 320                disk_stack_limits(mddev->gendisk, rdev->bdev,
 321                                  rdev->data_offset << 9);
 322        }
 323
 324        md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 325        mddev->private = conf;
 326
 327        reshape(mddev);
 328
 329        return 0;
 330}
 331
 332static int stop(struct mddev *mddev)
 333{
 334        struct faulty_conf *conf = mddev->private;
 335
 336        kfree(conf);
 337        mddev->private = NULL;
 338        return 0;
 339}
 340
 341static struct md_personality faulty_personality =
 342{
 343        .name           = "faulty",
 344        .level          = LEVEL_FAULTY,
 345        .owner          = THIS_MODULE,
 346        .make_request   = make_request,
 347        .run            = run,
 348        .stop           = stop,
 349        .status         = status,
 350        .check_reshape  = reshape,
 351        .size           = faulty_size,
 352};
 353
 354static int __init raid_init(void)
 355{
 356        return register_md_personality(&faulty_personality);
 357}
 358
 359static void raid_exit(void)
 360{
 361        unregister_md_personality(&faulty_personality);
 362}
 363
 364module_init(raid_init);
 365module_exit(raid_exit);
 366MODULE_LICENSE("GPL");
 367MODULE_DESCRIPTION("Fault injection personality for MD");
 368MODULE_ALIAS("md-personality-10"); /* faulty */
 369MODULE_ALIAS("md-faulty");
 370MODULE_ALIAS("md-level--5");
 371
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.