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 recurrance 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/raid/md_u.h>
  67 #include "md.h"
  68 #include <linux/seq_file.h>
  69
  70
  71 static void faulty_fail(struct bio *bio, int error)
  72 {
  73         struct bio *b = bio->bi_private;
  74
  75         b->bi_size = bio->bi_size;
  76         b->bi_sector = bio->bi_sector;
  77
  78         bio_put(bio);
  79
  80         bio_io_error(b);
  81 }
  82
  83 typedef struct faulty_conf {
  84         int period[Modes];
  85         atomic_t counters[Modes];
  86         sector_t faults[MaxFault];
  87         int     modes[MaxFault];
  88         int nfaults;
  89         mdk_rdev_t *rdev;
  90 } conf_t;
  91
  92 static int check_mode(conf_t *conf, int mode)
  93 {
  94         if (conf->period[mode] == 0 &&
  95             atomic_read(&conf->counters[mode]) <= 0)
  96                 return 0; /* no failure, no decrement */
  97
  98
  99         if (atomic_dec_and_test(&conf->counters[mode])) {
 100                 if (conf->period[mode])
 101                         atomic_set(&conf->counters[mode], conf->period[mode]);
 102                 return 1;
 103         }
 104         return 0;
 105 }
 106
 107 static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
 108 {
 109         /* If we find a ReadFixable sector, we fix it ... */
 110         int i;
 111         for (i=0; i<conf->nfaults; i++)
 112                 if (conf->faults[i] >= start &&
 113                     conf->faults[i] < end) {
 114                         /* found it ... */
 115                         switch (conf->modes[i] * 2 + dir) {
 116                         case WritePersistent*2+WRITE: return 1;
 117                         case ReadPersistent*2+READ: return 1;
 118                         case ReadFixable*2+READ: return 1;
 119                         case ReadFixable*2+WRITE:
 120                                 conf->modes[i] = NoPersist;
 121                                 return 0;
 122                         case AllPersist*2+READ:
 123                         case AllPersist*2+WRITE: return 1;
 124                         default:
 125                                 return 0;
 126                         }
 127                 }
 128         return 0;
 129 }
 130
 131 static void add_sector(conf_t *conf, sector_t start, int mode)
 132 {
 133         int i;
 134         int n = conf->nfaults;
 135         for (i=0; i<conf->nfaults; i++)
 136                 if (conf->faults[i] == start) {
 137                         switch(mode) {
 138                         case NoPersist: conf->modes[i] = mode; return;
 139                         case WritePersistent:
 140                                 if (conf->modes[i] == ReadPersistent ||
 141                                     conf->modes[i] == ReadFixable)
 142                                         conf->modes[i] = AllPersist;
 143                                 else
 144                                         conf->modes[i] = WritePersistent;
 145                                 return;
 146                         case ReadPersistent:
 147                                 if (conf->modes[i] == WritePersistent)
 148                                         conf->modes[i] = AllPersist;
 149                                 else
 150                                         conf->modes[i] = ReadPersistent;
 151                                 return;
 152                         case ReadFixable:
 153                                 if (conf->modes[i] == WritePersistent ||
 154                                     conf->modes[i] == ReadPersistent)
 155                                         conf->modes[i] = AllPersist;
 156                                 else
 157                                         conf->modes[i] = ReadFixable;
 158                                 return;
 159                         }
 160                 } else if (conf->modes[i] == NoPersist)
 161                         n = i;
 162
 163         if (n >= MaxFault)
 164                 return;
 165         conf->faults[n] = start;
 166         conf->modes[n] = mode;
 167         if (conf->nfaults == n)
 168                 conf->nfaults = n+1;
 169 }
 170
 171 static int make_request(struct request_queue *q, struct bio *bio)
 172 {
 173         mddev_t *mddev = q->queuedata;
 174         conf_t *conf = (conf_t*)mddev->private;
 175         int failit = 0;
 176
 177         if (bio_data_dir(bio) == WRITE) {
 178                 /* write request */
 179                 if (atomic_read(&conf->counters[WriteAll])) {
 180                         /* special case - don't decrement, don't generic_make_request,
 181                          * just fail immediately
 182                          */
 183                         bio_endio(bio, -EIO);
 184                         return 0;
 185                 }
 186
 187                 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
 188                                  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->bi_sector + (bio->bi_size>>9),
 199                                  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(bio, GFP_NOIO);
 214                 b->bi_bdev = conf->rdev->bdev;
 215                 b->bi_private = bio;
 216                 b->bi_end_io = faulty_fail;
 217                 generic_make_request(b);
 218                 return 0;
 219         } else {
 220                 bio->bi_bdev = conf->rdev->bdev;
 221                 return 1;
 222         }
 223 }
 224
 225 static void status(struct seq_file *seq, mddev_t *mddev)
 226 {
 227         conf_t *conf = (conf_t*)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 reconfig(mddev_t *mddev, int layout, int chunk_size)
 259 {
 260         int mode = layout & ModeMask;
 261         int count = layout >> ModeShift;
 262         conf_t *conf = mddev->private;
 263
 264         if (chunk_size != -1)
 265                 return -EINVAL;
 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->layout = -1; /* makes sure further changes come through */
 283         return 0;
 284 }
 285
 286 static sector_t faulty_size(mddev_t *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(mddev_t *mddev)
 298 {
 299         mdk_rdev_t *rdev;
 300         int i;
 301
 302         conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 303         if (!conf)
 304                 return -ENOMEM;
 305
 306         for (i=0; i<Modes; i++) {
 307                 atomic_set(&conf->counters[i], 0);
 308                 conf->period[i] = 0;
 309         }
 310         conf->nfaults = 0;
 311
 312         list_for_each_entry(rdev, &mddev->disks, same_set)
 313                 conf->rdev = rdev;
 314
 315         md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 316         mddev->private = conf;
 317
 318         reconfig(mddev, mddev->layout, -1);
 319
 320         return 0;
 321 }
 322
 323 static int stop(mddev_t *mddev)
 324 {
 325         conf_t *conf = (conf_t *)mddev->private;
 326
 327         kfree(conf);
 328         mddev->private = NULL;
 329         return 0;
 330 }
 331
 332 static struct mdk_personality faulty_personality =
 333 {
 334         .name           = "faulty",
 335         .level          = LEVEL_FAULTY,
 336         .owner          = THIS_MODULE,
 337         .make_request   = make_request,
 338         .run            = run,
 339         .stop           = stop,
 340         .status         = status,
 341         .reconfig       = reconfig,
 342         .size           = faulty_size,
 343 };
 344
 345 static int __init raid_init(void)
 346 {
 347         return register_md_personality(&faulty_personality);
 348 }
 349
 350 static void raid_exit(void)
 351 {
 352         unregister_md_personality(&faulty_personality);
 353 }
 354
 355 module_init(raid_init);
 356 module_exit(raid_exit);
 357 MODULE_LICENSE("GPL");
 358 MODULE_ALIAS("md-personality-10"); /* faulty */
 359 MODULE_ALIAS("md-faulty");
 360 MODULE_ALIAS("md-level--5");