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 };
  29
  30 /*
  31  * Construct a flakey mapping: <dev_path> <offset> <up interval> <down interval>
  32  */
  33 static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  34 {
  35         struct flakey_c *fc;
  36         unsigned long long tmp;
  37
  38         if (argc != 4) {
  39                 ti->error = "dm-flakey: Invalid argument count";
  40                 return -EINVAL;
  41         }
  42
  43         fc = kmalloc(sizeof(*fc), GFP_KERNEL);
  44         if (!fc) {
  45                 ti->error = "dm-flakey: Cannot allocate linear context";
  46                 return -ENOMEM;
  47         }
  48         fc->start_time = jiffies;
  49
  50         if (sscanf(argv[1], "%llu", &tmp) != 1) {
  51                 ti->error = "dm-flakey: Invalid device sector";
  52                 goto bad;
  53         }
  54         fc->start = tmp;
  55
  56         if (sscanf(argv[2], "%u", &fc->up_interval) != 1) {
  57                 ti->error = "dm-flakey: Invalid up interval";
  58                 goto bad;
  59         }
  60
  61         if (sscanf(argv[3], "%u", &fc->down_interval) != 1) {
  62                 ti->error = "dm-flakey: Invalid down interval";
  63                 goto bad;
  64         }
  65
  66         if (!(fc->up_interval + fc->down_interval)) {
  67                 ti->error = "dm-flakey: Total (up + down) interval is zero";
  68                 goto bad;
  69         }
  70
  71         if (fc->up_interval + fc->down_interval < fc->up_interval) {
  72                 ti->error = "dm-flakey: Interval overflow";
  73                 goto bad;
  74         }
  75
  76         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &fc->dev)) {
  77                 ti->error = "dm-flakey: Device lookup failed";
  78                 goto bad;
  79         }
  80
  81         ti->num_flush_requests = 1;
  82         ti->private = fc;
  83         return 0;
  84
  85 bad:
  86         kfree(fc);
  87         return -EINVAL;
  88 }
  89
  90 static void flakey_dtr(struct dm_target *ti)
  91 {
  92         struct flakey_c *fc = ti->private;
  93
  94         dm_put_device(ti, fc->dev);
  95         kfree(fc);
  96 }
  97
  98 static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
  99 {
 100         struct flakey_c *fc = ti->private;
 101
 102         return fc->start + (bi_sector - ti->begin);
 103 }
 104
 105 static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
 106 {
 107         struct flakey_c *fc = ti->private;
 108
 109         bio->bi_bdev = fc->dev->bdev;
 110         if (bio_sectors(bio))
 111                 bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
 112 }
 113
 114 static int flakey_map(struct dm_target *ti, struct bio *bio,
 115                       union map_info *map_context)
 116 {
 117         struct flakey_c *fc = ti->private;
 118         unsigned elapsed;
 119
 120         /* Are we alive ? */
 121         elapsed = (jiffies - fc->start_time) / HZ;
 122         if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval)
 123                 return -EIO;
 124
 125         flakey_map_bio(ti, bio);
 126
 127         return DM_MAPIO_REMAPPED;
 128 }
 129
 130 static int flakey_status(struct dm_target *ti, status_type_t type,
 131                          char *result, unsigned int maxlen)
 132 {
 133         struct flakey_c *fc = ti->private;
 134
 135         switch (type) {
 136         case STATUSTYPE_INFO:
 137                 result[0] = '\0';
 138                 break;
 139
 140         case STATUSTYPE_TABLE:
 141                 snprintf(result, maxlen, "%s %llu %u %u", fc->dev->name,
 142                          (unsigned long long)fc->start, fc->up_interval,
 143                          fc->down_interval);
 144                 break;
 145         }
 146         return 0;
 147 }
 148
 149 static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
 150 {
 151         struct flakey_c *fc = ti->private;
 152
 153         return __blkdev_driver_ioctl(fc->dev->bdev, fc->dev->mode, cmd, arg);
 154 }
 155
 156 static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 157                         struct bio_vec *biovec, int max_size)
 158 {
 159         struct flakey_c *fc = ti->private;
 160         struct request_queue *q = bdev_get_queue(fc->dev->bdev);
 161
 162         if (!q->merge_bvec_fn)
 163                 return max_size;
 164
 165         bvm->bi_bdev = fc->dev->bdev;
 166         bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
 167
 168         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 169 }
 170
 171 static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
 172 {
 173         struct flakey_c *fc = ti->private;
 174
 175         return fn(ti, fc->dev, fc->start, ti->len, data);
 176 }
 177
 178 static struct target_type flakey_target = {
 179         .name   = "flakey",
 180         .version = {1, 1, 0},
 181         .module = THIS_MODULE,
 182         .ctr    = flakey_ctr,
 183         .dtr    = flakey_dtr,
 184         .map    = flakey_map,
 185         .status = flakey_status,
 186         .ioctl  = flakey_ioctl,
 187         .merge  = flakey_merge,
 188         .iterate_devices = flakey_iterate_devices,
 189 };
 190
 191 static int __init dm_flakey_init(void)
 192 {
 193         int r = dm_register_target(&flakey_target);
 194
 195         if (r < 0)
 196                 DMERR("register failed %d", r);
 197
 198         return r;
 199 }
 200
 201 static void __exit dm_flakey_exit(void)
 202 {
 203         dm_unregister_target(&flakey_target);
 204 }
 205
 206 /* Module hooks */
 207 module_init(dm_flakey_init);
 208 module_exit(dm_flakey_exit);
 209
 210 MODULE_DESCRIPTION(DM_NAME " flakey target");
 211 MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
 212 MODULE_LICENSE("GPL");