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 int faulty_fail(struct bio *bio, unsigned int bytes_done, 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         if (bio->bi_size == 0)
  76                 bio_put(bio);
  77
  78         clear_bit(BIO_UPTODATE, &b->bi_flags);
  79         return (b->bi_end_io)(b, bytes_done, -EIO);
  80 }
  81
  82 typedef struct faulty_conf {
  83         int period[Modes];
  84         atomic_t counters[Modes];
  85         sector_t faults[MaxFault];
  86         int     modes[MaxFault];
  87         int nfaults;
  88         mdk_rdev_t *rdev;
  89 } conf_t;
  90
  91 static int check_mode(conf_t *conf, int mode)
  92 {
  93         if (conf->period[mode] == 0 &&
  94             atomic_read(&conf->counters[mode]) <= 0)
  95                 return 0; /* no failure, no decrement */
  96
  97
  98         if (atomic_dec_and_test(&conf->counters[mode])) {
  99                 if (conf->period[mode])
 100                         atomic_set(&conf->counters[mode], conf->period[mode]);
 101                 return 1;
 102         }
 103         return 0;
 104 }
 105
 106 static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
 107 {
 108         /* If we find a ReadFixable sector, we fix it ... */
 109         int i;
 110         for (i=0; i<conf->nfaults; i++)
 111                 if (conf->faults[i] >= start &&
 112                     conf->faults[i] < end) {
 113                         /* found it ... */
 114                         switch (conf->modes[i] * 2 + dir) {
 115                         case WritePersistent*2+WRITE: return 1;
 116                         case ReadPersistent*2+READ: return 1;
 117                         case ReadFixable*2+READ: return 1;
 118                         case ReadFixable*2+WRITE:
 119                                 conf->modes[i] = NoPersist;
 120                                 return 0;
 121                         case AllPersist*2+READ:
 122                         case AllPersist*2+WRITE: return 1;
 123                         default:
 124                                 return 0;
 125                         }
 126                 }
 127         return 0;
 128 }
 129
 130 static void add_sector(conf_t *conf, sector_t start, int mode)
 131 {
 132         int i;
 133         int n = conf->nfaults;
 134         for (i=0; i<conf->nfaults; i++)
 135                 if (conf->faults[i] == start) {
 136                         switch(mode) {
 137                         case NoPersist: conf->modes[i] = mode; return;
 138                         case WritePersistent:
 139                                 if (conf->modes[i] == ReadPersistent ||
 140                                     conf->modes[i] == ReadFixable)
 141                                         conf->modes[i] = AllPersist;
 142                                 else
 143                                         conf->modes[i] = WritePersistent;
 144                                 return;
 145                         case ReadPersistent:
 146                                 if (conf->modes[i] == WritePersistent)
 147                                         conf->modes[i] = AllPersist;
 148                                 else
 149                                         conf->modes[i] = ReadPersistent;
 150                                 return;
 151                         case ReadFixable:
 152                                 if (conf->modes[i] == WritePersistent ||
 153                                     conf->modes[i] == ReadPersistent)
 154                                         conf->modes[i] = AllPersist;
 155                                 else
 156                                         conf->modes[i] = ReadFixable;
 157                                 return;
 158                         }
 159                 } else if (conf->modes[i] == NoPersist)
 160                         n = i;
 161
 162         if (n >= MaxFault)
 163                 return;
 164         conf->faults[n] = start;
 165         conf->modes[n] = mode;
 166         if (conf->nfaults == n)
 167                 conf->nfaults = n+1;
 168 }
 169
 170 static int make_request(request_queue_t *q, struct bio *bio)
 171 {
 172         mddev_t *mddev = q->queuedata;
 173         conf_t *conf = (conf_t*)mddev->private;
 174         int failit = 0;
 175
 176         if (bio->bi_rw & 1) {
 177                 /* write request */
 178                 if (atomic_read(&conf->counters[WriteAll])) {
 179                         /* special case - don't decrement, don't generic_make_request,
 180                          * just fail immediately
 181                          */
 182                         bio_endio(bio, bio->bi_size, -EIO);
 183                         return 0;
 184                 }
 185
 186                 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
 187                                  WRITE))
 188                         failit = 1;
 189                 if (check_mode(conf, WritePersistent)) {
 190                         add_sector(conf, bio->bi_sector, WritePersistent);
 191                         failit = 1;
 192                 }
 193                 if (check_mode(conf, WriteTransient))
 194                         failit = 1;
 195         } else {
 196                 /* read request */
 197                 if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
 198                                  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(bio, GFP_NOIO);
 213                 b->bi_bdev = conf->rdev->bdev;
 214                 b->bi_private = bio;
 215                 b->bi_end_io = faulty_fail;
 216                 generic_make_request(b);
 217                 return 0;
 218         } else {
 219                 bio->bi_bdev = conf->rdev->bdev;
 220                 return 1;
 221         }
 222 }
 223
 224 static void status(struct seq_file *seq, mddev_t *mddev)
 225 {
 226         conf_t *conf = (conf_t*)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
 257 static int reconfig(mddev_t *mddev, int layout, int chunk_size)
 258 {
 259         int mode = layout & ModeMask;
 260         int count = layout >> ModeShift;
 261         conf_t *conf = mddev->private;
 262
 263         if (chunk_size != -1)
 264                 return -EINVAL;
 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->layout = -1; /* makes sure further changes come through */
 282         return 0;
 283 }
 284
 285 static int run(mddev_t *mddev)
 286 {
 287         mdk_rdev_t *rdev;
 288         struct list_head *tmp;
 289         int i;
 290
 291         conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
 292
 293         for (i=0; i<Modes; i++) {
 294                 atomic_set(&conf->counters[i], 0);
 295                 conf->period[i] = 0;
 296         }
 297         conf->nfaults = 0;
 298
 299         ITERATE_RDEV(mddev, rdev, tmp)
 300                 conf->rdev = rdev;
 301
 302         mddev->array_size = mddev->size;
 303         mddev->private = conf;
 304
 305         reconfig(mddev, mddev->layout, -1);
 306
 307         return 0;
 308 }
 309
 310 static int stop(mddev_t *mddev)
 311 {
 312         conf_t *conf = (conf_t *)mddev->private;
 313
 314         kfree(conf);
 315         mddev->private = NULL;
 316         return 0;
 317 }
 318
 319 static mdk_personality_t faulty_personality =
 320 {
 321         .name           = "faulty",
 322         .owner          = THIS_MODULE,
 323         .make_request   = make_request,
 324         .run            = run,
 325         .stop           = stop,
 326         .status         = status,
 327         .reconfig       = reconfig,
 328 };
 329
 330 static int __init raid_init(void)
 331 {
 332         return register_md_personality(FAULTY, &faulty_personality);
 333 }
 334
 335 static void raid_exit(void)
 336 {
 337         unregister_md_personality(FAULTY);
 338 }
 339
 340 module_init(raid_init);
 341 module_exit(raid_exit);
 342 MODULE_LICENSE("GPL");
 343 MODULE_ALIAS("md-personality-10"); /* faulty */