drivers/md/dm-flakey.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software (UK) Limited.
   3  * Copyright (C) 2004, 2010 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/blkdev.h>
  13 #include <linux/bio.h>
  14 #include <linux/slab.h>
  15
  16 #define DM_MSG_PREFIX "flakey"
  17
  18 /*
  19  * Flakey: Used for testing only, simulates intermittent,
  20  * catastrophic device failure.
  21  */
  22 struct flakey_c {
  23         struct dm_dev *dev;
  24         unsigned long start_time;
  25         sector_t start;
  26         unsigned up_interval;
  27         unsigned down_interval;
  28         unsigned long flags;
  29 };
  30
  31 enum feature_flag_bits {
  32         DROP_WRITES
  33 };
  34
  35 static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
  36                           struct dm_target *ti)
  37 {
  38         int r;
  39         unsigned argc;
  40         const char *arg_name;
  41
  42         static struct dm_arg _args[] = {
  43                 {0, 1, "Invalid number of feature args"},
  44         };
  45
  46         /* No feature arguments supplied. */
  47         if (!as->argc)
  48                 return 0;
  49
  50         r = dm_read_arg_group(_args, as, &argc, &ti->error);
  51         if (r)
  52                 return -EINVAL;
  53
  54         while (argc && !r) {
  55                 arg_name = dm_shift_arg(as);
  56                 argc--;
  57
  58                 /*
  59                  * drop_writes
  60                  */
  61                 if (!strcasecmp(arg_name, "drop_writes")) {
  62                         if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
  63                                 ti->error = "Feature drop_writes duplicated";
  64                                 return -EINVAL;
  65                         }
  66
  67                         continue;
  68                 }
  69
  70                 ti->error = "Unrecognised flakey feature requested";
  71                 r = -EINVAL;
  72         }
  73
  74         return r;
  75 }
  76
  77 /*
  78  * Construct a flakey mapping:
  79  * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
  80  *
  81  *   Feature args:
  82  *     [drop_writes]
  83  */
  84 static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  85 {
  86         static struct dm_arg _args[] = {
  87                 {0, UINT_MAX, "Invalid up interval"},
  88                 {0, UINT_MAX, "Invalid down interval"},
  89         };
  90
  91         int r;
  92         struct flakey_c *fc;
  93         unsigned long long tmpll;
  94         struct dm_arg_set as;
  95         const char *devname;
  96
  97         as.argc = argc;
  98         as.argv = argv;
  99
 100         if (argc < 4) {
 101                 ti->error = "Invalid argument count";
 102                 return -EINVAL;
 103         }
 104
 105         fc = kzalloc(sizeof(*fc), GFP_KERNEL);
 106         if (!fc) {
 107                 ti->error = "Cannot allocate linear context";
 108                 return -ENOMEM;
 109         }
 110         fc->start_time = jiffies;
 111
 112         devname = dm_shift_arg(&as);
 113
 114         if (sscanf(dm_shift_arg(&as), "%llu", &tmpll) != 1) {
 115                 ti->error = "Invalid device sector";
 116                 goto bad;
 117         }
 118         fc->start = tmpll;
 119
 120         r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
 121         if (r)
 122                 goto bad;
 123
 124         r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
 125         if (r)
 126                 goto bad;
 127
 128         if (!(fc->up_interval + fc->down_interval)) {
 129                 ti->error = "Total (up + down) interval is zero";
 130                 goto bad;
 131         }
 132
 133         if (fc->up_interval + fc->down_interval < fc->up_interval) {
 134                 ti->error = "Interval overflow";
 135                 goto bad;
 136         }
 137
 138         r = parse_features(&as, fc, ti);
 139         if (r)
 140                 goto bad;
 141
 142         if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
 143                 ti->error = "Device lookup failed";
 144                 goto bad;
 145         }
 146
 147         ti->num_flush_requests = 1;
 148         ti->num_discard_requests = 1;
 149         ti->private = fc;
 150         return 0;
 151
 152 bad:
 153         kfree(fc);
 154         return -EINVAL;
 155 }
 156
 157 static void flakey_dtr(struct dm_target *ti)
 158 {
 159         struct flakey_c *fc = ti->private;
 160
 161         dm_put_device(ti, fc->dev);
 162         kfree(fc);
 163 }
 164
 165 static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
 166 {
 167         struct flakey_c *fc = ti->private;
 168
 169         return fc->start + dm_target_offset(ti, bi_sector);
 170 }
 171
 172 static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 173 {
 174         struct flakey_c *fc = ti->private;
 175
 176         bio->bi_bdev = fc->dev->bdev;
 177         if (bio_sectors(bio))
 178                 bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
 179 }
 180
 181 static int flakey_map(struct dm_target *ti, struct bio *bio,
 182                       union map_info *map_context)
 183 {
 184         struct flakey_c *fc = ti->private;
 185         unsigned elapsed;
 186         unsigned rw;
 187
 188         /* Are we alive ? */
 189         elapsed = (jiffies - fc->start_time) / HZ;
 190         if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
 191                 rw = bio_data_dir(bio);
 192
 193                 /*
 194                  * Drop writes.  Map reads as normal.
 195                  */
 196                 if (test_bit(DROP_WRITES, &fc->flags)) {
 197                         if (rw == WRITE) {
 198                                 bio_endio(bio, 0);
 199                                 return DM_MAPIO_SUBMITTED;
 200                         }
 201                         goto map_bio;
 202                 }
 203
 204                 /*
 205                  * Default setting errors all I/O.
 206                  */
 207                 return -EIO;
 208         }
 209
 210 map_bio:
 211         flakey_map_bio(ti, bio);
 212
 213         return DM_MAPIO_REMAPPED;
 214 }
 215
 216 static int flakey_status(struct dm_target *ti, status_type_t type,
 217                          char *result, unsigned int maxlen)
 218 {
 219         unsigned sz = 0;
 220         struct flakey_c *fc = ti->private;
 221         unsigned drop_writes;
 222
 223         switch (type) {
 224         case STATUSTYPE_INFO:
 225                 result[0] = '\0';
 226                 break;
 227
 228         case STATUSTYPE_TABLE:
 229                 DMEMIT("%s %llu %u %u ", fc->dev->name,
 230                        (unsigned long long)fc->start, fc->up_interval,
 231                        fc->down_interval);
 232
 233                 drop_writes = test_bit(DROP_WRITES, &fc->flags);
 234                 DMEMIT("%u ", drop_writes);
 235                 if (drop_writes)
 236                         DMEMIT("drop_writes ");
 237                 break;
 238         }
 239         return 0;
 240 }
 241
 242 static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
 243 {
 244         struct flakey_c *fc = ti->private;
 245
 246         return __blkdev_driver_ioctl(fc->dev->bdev, fc->dev->mode, cmd, arg);
 247 }
 248
 249 static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 250                         struct bio_vec *biovec, int max_size)
 251 {
 252         struct flakey_c *fc = ti->private;
 253         struct request_queue *q = bdev_get_queue(fc->dev->bdev);
 254
 255         if (!q->merge_bvec_fn)
 256                 return max_size;
 257
 258         bvm->bi_bdev = fc->dev->bdev;
 259         bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
 260
 261         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 262 }
 263
 264 static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
 265 {
 266         struct flakey_c *fc = ti->private;
 267
 268         return fn(ti, fc->dev, fc->start, ti->len, data);
 269 }
 270
 271 static struct target_type flakey_target = {
 272         .name   = "flakey",
 273         .version = {1, 2, 0},
 274         .module = THIS_MODULE,
 275         .ctr    = flakey_ctr,
 276         .dtr    = flakey_dtr,
 277         .map    = flakey_map,
 278         .status = flakey_status,
 279         .ioctl  = flakey_ioctl,
 280         .merge  = flakey_merge,
 281         .iterate_devices = flakey_iterate_devices,
 282 };
 283
 284 static int __init dm_flakey_init(void)
 285 {
 286         int r = dm_register_target(&flakey_target);
 287
 288         if (r < 0)
 289                 DMERR("register failed %d", r);
 290
 291         return r;
 292 }
 293
 294 static void __exit dm_flakey_exit(void)
 295 {
 296         dm_unregister_target(&flakey_target);
 297 }
 298
 299 /* Module hooks */
 300 module_init(dm_flakey_init);
 301 module_exit(dm_flakey_exit);
 302
 303 MODULE_DESCRIPTION(DM_NAME " flakey target");
 304 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 305 MODULE_LICENSE("GPL");