release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/md/dm-snap-transient.c

   1 /*
   2  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   3  * Copyright (C) 2006-2008 Red Hat GmbH
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include "dm-exception-store.h"
   9
  10 #include <linux/mm.h>
  11 #include <linux/pagemap.h>
  12 #include <linux/vmalloc.h>
  13 #include <linux/slab.h>
  14 #include <linux/dm-io.h>
  15
  16 #define DM_MSG_PREFIX "transient snapshot"
  17
  18 /*-----------------------------------------------------------------
  19  * Implementation of the store for non-persistent snapshots.
  20  *---------------------------------------------------------------*/
  21 struct transient_c {
  22         sector_t next_free;
  23 };
  24
  25 static void transient_dtr(struct dm_exception_store *store)
  26 {
  27         kfree(store->context);
  28 }
  29
  30 static int transient_read_metadata(struct dm_exception_store *store,
  31                                    int (*callback)(void *callback_context,
  32                                                    chunk_t old, chunk_t new),
  33                                    void *callback_context)
  34 {
  35         return 0;
  36 }
  37
  38 static int transient_prepare_exception(struct dm_exception_store *store,
  39                                        struct dm_exception *e)
  40 {
  41         struct transient_c *tc = store->context;
  42         sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
  43
  44         if (size < (tc->next_free + store->chunk_size))
  45                 return -1;
  46
  47         e->new_chunk = sector_to_chunk(store, tc->next_free);
  48         tc->next_free += store->chunk_size;
  49
  50         return 0;
  51 }
  52
  53 static void transient_commit_exception(struct dm_exception_store *store,
  54                                        struct dm_exception *e,
  55                                        void (*callback) (void *, int success),
  56                                        void *callback_context)
  57 {
  58         /* Just succeed */
  59         callback(callback_context, 1);
  60 }
  61
  62 static void transient_usage(struct dm_exception_store *store,
  63                             sector_t *total_sectors,
  64                             sector_t *sectors_allocated,
  65                             sector_t *metadata_sectors)
  66 {
  67         *sectors_allocated = ((struct transient_c *) store->context)->next_free;
  68         *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
  69         *metadata_sectors = 0;
  70 }
  71
  72 static int transient_ctr(struct dm_exception_store *store,
  73                          unsigned argc, char **argv)
  74 {
  75         struct transient_c *tc;
  76
  77         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  78         if (!tc)
  79                 return -ENOMEM;
  80
  81         tc->next_free = 0;
  82         store->context = tc;
  83
  84         return 0;
  85 }
  86
  87 static unsigned transient_status(struct dm_exception_store *store,
  88                                  status_type_t status, char *result,
  89                                  unsigned maxlen)
  90 {
  91         unsigned sz = 0;
  92
  93         switch (status) {
  94         case STATUSTYPE_INFO:
  95                 break;
  96         case STATUSTYPE_TABLE:
  97                 DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
  98         }
  99
 100         return sz;
 101 }
 102
 103 static struct dm_exception_store_type _transient_type = {
 104         .name = "transient",
 105         .module = THIS_MODULE,
 106         .ctr = transient_ctr,
 107         .dtr = transient_dtr,
 108         .read_metadata = transient_read_metadata,
 109         .prepare_exception = transient_prepare_exception,
 110         .commit_exception = transient_commit_exception,
 111         .usage = transient_usage,
 112         .status = transient_status,
 113 };
 114
 115 static struct dm_exception_store_type _transient_compat_type = {
 116         .name = "N",
 117         .module = THIS_MODULE,
 118         .ctr = transient_ctr,
 119         .dtr = transient_dtr,
 120         .read_metadata = transient_read_metadata,
 121         .prepare_exception = transient_prepare_exception,
 122         .commit_exception = transient_commit_exception,
 123         .usage = transient_usage,
 124         .status = transient_status,
 125 };
 126
 127 int dm_transient_snapshot_init(void)
 128 {
 129         int r;
 130
 131         r = dm_exception_store_type_register(&_transient_type);
 132         if (r) {
 133                 DMWARN("Unable to register transient exception store type");
 134                 return r;
 135         }
 136
 137         r = dm_exception_store_type_register(&_transient_compat_type);
 138         if (r) {
 139                 DMWARN("Unable to register old-style transient "
 140                        "exception store type");
 141                 dm_exception_store_type_unregister(&_transient_type);
 142                 return r;
 143         }
 144
 145         return r;
 146 }
 147
 148 void dm_transient_snapshot_exit(void)
 149 {
 150         dm_exception_store_type_unregister(&_transient_type);
 151         dm_exception_store_type_unregister(&_transient_compat_type);
 152 }