drivers/md/dm-linear.c

   1 /*
   2  * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include "dm.h"
   8 #include <linux/module.h>
   9 #include <linux/init.h>
  10 #include <linux/blkdev.h>
  11 #include <linux/bio.h>
  12 #include <linux/slab.h>
  13 #include <linux/device-mapper.h>
  14
  15 #define DM_MSG_PREFIX "linear"
  16
  17 /*
  18  * Linear: maps a linear range of a device.
  19  */
  20 struct linear_c {
  21         struct dm_dev *dev;
  22         sector_t start;
  23 };
  24
  25 /*
  26  * Construct a linear mapping: <dev_path> <offset>
  27  */
  28 static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  29 {
  30         struct linear_c *lc;
  31         unsigned long long tmp;
  32         char dummy;
  33
  34         if (argc != 2) {
  35                 ti->error = "Invalid argument count";
  36                 return -EINVAL;
  37         }
  38
  39         lc = kmalloc(sizeof(*lc), GFP_KERNEL);
  40         if (lc == NULL) {
  41                 ti->error = "dm-linear: Cannot allocate linear context";
  42                 return -ENOMEM;
  43         }
  44
  45         if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1) {
  46                 ti->error = "dm-linear: Invalid device sector";
  47                 goto bad;
  48         }
  49         lc->start = tmp;
  50
  51         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &lc->dev)) {
  52                 ti->error = "dm-linear: Device lookup failed";
  53                 goto bad;
  54         }
  55
  56         ti->num_flush_requests = 1;
  57         ti->num_discard_requests = 1;
  58         ti->private = lc;
  59         return 0;
  60
  61       bad:
  62         kfree(lc);
  63         return -EINVAL;
  64 }
  65
  66 static void linear_dtr(struct dm_target *ti)
  67 {
  68         struct linear_c *lc = (struct linear_c *) ti->private;
  69
  70         dm_put_device(ti, lc->dev);
  71         kfree(lc);
  72 }
  73
  74 static sector_t linear_map_sector(struct dm_target *ti, sector_t bi_sector)
  75 {
  76         struct linear_c *lc = ti->private;
  77
  78         return lc->start + dm_target_offset(ti, bi_sector);
  79 }
  80
  81 static void linear_map_bio(struct dm_target *ti, struct bio *bio)
  82 {
  83         struct linear_c *lc = ti->private;
  84
  85         bio->bi_bdev = lc->dev->bdev;
  86         if (bio_sectors(bio))
  87                 bio->bi_sector = linear_map_sector(ti, bio->bi_sector);
  88 }
  89
  90 static int linear_map(struct dm_target *ti, struct bio *bio,
  91                       union map_info *map_context)
  92 {
  93         linear_map_bio(ti, bio);
  94
  95         return DM_MAPIO_REMAPPED;
  96 }
  97
  98 static int linear_status(struct dm_target *ti, status_type_t type,
  99                          unsigned status_flags, char *result, unsigned maxlen)
 100 {
 101         struct linear_c *lc = (struct linear_c *) ti->private;
 102
 103         switch (type) {
 104         case STATUSTYPE_INFO:
 105                 result[0] = '\0';
 106                 break;
 107
 108         case STATUSTYPE_TABLE:
 109                 snprintf(result, maxlen, "%s %llu", lc->dev->name,
 110                                 (unsigned long long)lc->start);
 111                 break;
 112         }
 113         return 0;
 114 }
 115
 116 static int linear_ioctl(struct dm_target *ti, unsigned int cmd,
 117                         unsigned long arg)
 118 {
 119         struct linear_c *lc = (struct linear_c *) ti->private;
 120         struct dm_dev *dev = lc->dev;
 121         int r = 0;
 122
 123         /*
 124          * Only pass ioctls through if the device sizes match exactly.
 125          */
 126         if (lc->start ||
 127             ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 128                 r = scsi_verify_blk_ioctl(NULL, cmd);
 129
 130         return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
 131 }
 132
 133 static int linear_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 134                         struct bio_vec *biovec, int max_size)
 135 {
 136         struct linear_c *lc = ti->private;
 137         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 138
 139         if (!q->merge_bvec_fn)
 140                 return max_size;
 141
 142         bvm->bi_bdev = lc->dev->bdev;
 143         bvm->bi_sector = linear_map_sector(ti, bvm->bi_sector);
 144
 145         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 146 }
 147
 148 static int linear_iterate_devices(struct dm_target *ti,
 149                                   iterate_devices_callout_fn fn, void *data)
 150 {
 151         struct linear_c *lc = ti->private;
 152
 153         return fn(ti, lc->dev, lc->start, ti->len, data);
 154 }
 155
 156 static struct target_type linear_target = {
 157         .name   = "linear",
 158         .version = {1, 1, 0},
 159         .module = THIS_MODULE,
 160         .ctr    = linear_ctr,
 161         .dtr    = linear_dtr,
 162         .map    = linear_map,
 163         .status = linear_status,
 164         .ioctl  = linear_ioctl,
 165         .merge  = linear_merge,
 166         .iterate_devices = linear_iterate_devices,
 167 };
 168
 169 int __init dm_linear_init(void)
 170 {
 171         int r = dm_register_target(&linear_target);
 172
 173         if (r < 0)
 174                 DMERR("register failed %d", r);
 175
 176         return r;
 177 }
 178
 179 void dm_linear_exit(void)
 180 {
 181         dm_unregister_target(&linear_target);
 182 }