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/raid/md.h>
  66
  67
  68 static void faulty_fail(struct bio *bio, int error)
  69 {
  70         struct bio *b = bio->bi_private;
  71
  72         b->bi_size = bio->bi_size;
  73         b->bi_sector = bio->bi_sector;
  74
  75         bio_put(bio);
  76
  77         bio_io_error(b);
  78 }
  79
  80 typedef struct faulty_conf {
  81         int period[Modes];
  82         atomic_t counters[Modes];
  83         sector_t faults[MaxFault];
  84         int     modes[MaxFault];
  85         int nfaults;
  86         mdk_rdev_t *rdev;
  87 } conf_t;
  88
  89 static int check_mode(conf_t *conf, int mode)
  90 {
  91         if (conf->period[mode] == 0 &&
  92             atomic_read(&conf->counters[mode]) <= 0)
  93                 return 0; /* no failure, no decrement */
  94
  95
  96         if (atomic_dec_and_test(&conf->counters[mode])) {
  97                 if (conf->period[mode])
  98                         atomic_set(&conf->counters[mode], conf->period[mode]);
  99                 return 1;
 100         }
 101         return 0;
 102 }
 103
 104 static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
 105 {
 106         /* If we find a ReadFixable sector, we fix it ... */
 107         int i;
 108         for (i=0; i<conf->nfaults; i++)
 109                 if (conf->faults[i] >= start &&
 110                     conf->faults[i] < end) {
 111                         /* found it ... */
 112                         switch (conf->modes[i] * 2 + dir) {
 113                         case WritePersistent*2+WRITE: return 1;
 114                         case ReadPersistent*2+READ: return 1;
 115                         case ReadFixable*2+READ: return 1;
 116                         case ReadFixable*2+WRITE:
 117                                 conf->modes[i] = NoPersist;
 118                                 return 0;
 119                         case AllPersist*2+READ:
 120                         case AllPersist*2+WRITE: return 1;
 121                         default:
 122                                 return 0;
 123                         }
 124                 }
 125         return 0;
 126 }
 127
 128 static void add_sector(conf_t *conf, sector_t start, int mode)
 129 {
 130         int i;
 131         int n = conf->nfaults;
 132         for (i=0; i<conf->nfaults; i++)
 133                 if (conf->faults[i] == start) {
 134                         switch(mode) {
 135                         case NoPersist: conf->modes[i] = mode; return;
 136                         case WritePersistent:
 137                                 if (conf->modes[i] == ReadPersistent ||
 138                                     conf->modes[i] == ReadFixable)
 139                                         conf->modes[i] = AllPersist;
 140                                 else
 141                                         conf->modes[i] = WritePersistent;
 142                                 return;
 143                         case ReadPersistent:
 144                                 if (conf->modes[i] == WritePersistent)
 145                                         conf->modes[i] = AllPersist;
 146                                 else
 147                                         conf->modes[i] = ReadPersistent;
 148                                 return;
 149                         case ReadFixable:
 150                                 if (conf->modes[i] == WritePersistent ||
 151                                     conf->modes[i] == ReadPersistent)
 152                                         conf->modes[i] = AllPersist;
 153                                 else
 154                                         conf->modes[i] = ReadFixable;
 155                                 return;
 156                         }
 157                 } else if (conf->modes[i] == NoPersist)
 158                         n = i;
 159
 160         if (n >= MaxFault)
 161                 return;
 162         conf->faults[n] = start;
 163         conf->modes[n] = mode;
 164         if (conf->nfaults == n)
 165                 conf->nfaults = n+1;
 166 }
 167
 168 static int make_request(struct request_queue *q, struct bio *bio)
 169 {
 170         mddev_t *mddev = q->queuedata;
 171         conf_t *conf = (conf_t*)mddev->private;
 172         int failit = 0;
 173
 174         if (bio_data_dir(bio) == WRITE) {
 175                 /* write request */
 176                 if (atomic_read(&conf->counters[WriteAll])) {
 177                         /* special case - don't decrement, don't generic_make_request,
 178                          * just fail immediately
 179                          */
 180                         bio_endio(bio, -EIO);
 181                         return 0;
 182                 }
 183
 184                 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
 185                                  WRITE))
 186                         failit = 1;
 187                 if (check_mode(conf, WritePersistent)) {
 188                         add_sector(conf, bio->bi_sector, WritePersistent);
 189                         failit = 1;
 190                 }
 191                 if (check_mode(conf, WriteTransient))
 192                         failit = 1;
 193         } else {
 194                 /* read request */
 195                 if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
 196                                  READ))
 197                         failit = 1;
 198                 if (check_mode(conf, ReadTransient))
 199                         failit = 1;
 200                 if (check_mode(conf, ReadPersistent)) {
 201                         add_sector(conf, bio->bi_sector, ReadPersistent);
 202                         failit = 1;
 203                 }
 204                 if (check_mode(conf, ReadFixable)) {
 205                         add_sector(conf, bio->bi_sector, ReadFixable);
 206                         failit = 1;
 207                 }
 208         }
 209         if (failit) {
 210                 struct bio *b = bio_clone(bio, GFP_NOIO);
 211                 b->bi_bdev = conf->rdev->bdev;
 212                 b->bi_private = bio;
 213                 b->bi_end_io = faulty_fail;
 214                 generic_make_request(b);
 215                 return 0;
 216         } else {
 217                 bio->bi_bdev = conf->rdev->bdev;
 218                 return 1;
 219         }
 220 }
 221
 222 static void status(struct seq_file *seq, mddev_t *mddev)
 223 {
 224         conf_t *conf = (conf_t*)mddev->private;
 225         int n;
 226
 227         if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
 228                 seq_printf(seq, " WriteTransient=%d(%d)",
 229                            n, conf->period[WriteTransient]);
 230
 231         if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
 232                 seq_printf(seq, " ReadTransient=%d(%d)",
 233                            n, conf->period[ReadTransient]);
 234
 235         if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
 236                 seq_printf(seq, " WritePersistent=%d(%d)",
 237                            n, conf->period[WritePersistent]);
 238
 239         if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
 240                 seq_printf(seq, " ReadPersistent=%d(%d)",
 241                            n, conf->period[ReadPersistent]);
 242
 243
 244         if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
 245                 seq_printf(seq, " ReadFixable=%d(%d)",
 246                            n, conf->period[ReadFixable]);
 247
 248         if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
 249                 seq_printf(seq, " WriteAll");
 250
 251         seq_printf(seq, " nfaults=%d", conf->nfaults);
 252 }
 253
 254
 255 static int reconfig(mddev_t *mddev, int layout, int chunk_size)
 256 {
 257         int mode = layout & ModeMask;
 258         int count = layout >> ModeShift;
 259         conf_t *conf = mddev->private;
 260
 261         if (chunk_size != -1)
 262                 return -EINVAL;
 263
 264         /* new layout */
 265         if (mode == ClearFaults)
 266                 conf->nfaults = 0;
 267         else if (mode == ClearErrors) {
 268                 int i;
 269                 for (i=0 ; i < Modes ; i++) {
 270                         conf->period[i] = 0;
 271                         atomic_set(&conf->counters[i], 0);
 272                 }
 273         } else if (mode < Modes) {
 274                 conf->period[mode] = count;
 275                 if (!count) count++;
 276                 atomic_set(&conf->counters[mode], count);
 277         } else
 278                 return -EINVAL;
 279         mddev->layout = -1; /* makes sure further changes come through */
 280         return 0;
 281 }
 282
 283 static int run(mddev_t *mddev)
 284 {
 285         mdk_rdev_t *rdev;
 286         struct list_head *tmp;
 287         int i;
 288
 289         conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 290
 291         for (i=0; i<Modes; i++) {
 292                 atomic_set(&conf->counters[i], 0);
 293                 conf->period[i] = 0;
 294         }
 295         conf->nfaults = 0;
 296
 297         rdev_for_each(rdev, tmp, mddev)
 298                 conf->rdev = rdev;
 299
 300         mddev->array_sectors = mddev->size * 2;
 301         mddev->private = conf;
 302
 303         reconfig(mddev, mddev->layout, -1);
 304
 305         return 0;
 306 }
 307
 308 static int stop(mddev_t *mddev)
 309 {
 310         conf_t *conf = (conf_t *)mddev->private;
 311
 312         kfree(conf);
 313         mddev->private = NULL;
 314         return 0;
 315 }
 316
 317 static struct mdk_personality faulty_personality =
 318 {
 319         .name           = "faulty",
 320         .level          = LEVEL_FAULTY,
 321         .owner          = THIS_MODULE,
 322         .make_request   = make_request,
 323         .run            = run,
 324         .stop           = stop,
 325         .status         = status,
 326         .reconfig       = reconfig,
 327 };
 328
 329 static int __init raid_init(void)
 330 {
 331         return register_md_personality(&faulty_personality);
 332 }
 333
 334 static void raid_exit(void)
 335 {
 336         unregister_md_personality(&faulty_personality);
 337 }
 338
 339 module_init(raid_init);
 340 module_exit(raid_exit);
 341 MODULE_LICENSE("GPL");
 342 MODULE_ALIAS("md-personality-10"); /* faulty */
 343 MODULE_ALIAS("md-faulty");
 344 MODULE_ALIAS("md-level--5");