linux/drivers/md/faulty.c
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   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_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
 224static 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
 257static 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
 286static 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
 297static 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
 330static 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
 339static 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
 352static int __init raid_init(void)
 353{
 354        return register_md_personality(&faulty_personality);
 355}
 356
 357static void raid_exit(void)
 358{
 359        unregister_md_personality(&faulty_personality);
 360}
 361
 362module_init(raid_init);
 363module_exit(raid_exit);
 364MODULE_LICENSE("GPL");
 365MODULE_DESCRIPTION("Fault injection personality for MD");
 366MODULE_ALIAS("md-personality-10"); /* faulty */
 367MODULE_ALIAS("md-faulty");
 368MODULE_ALIAS("md-level--5");
 369
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