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_snap_exception *e)
  40 {
  41         struct transient_c *tc = store->context;
  42         sector_t size = get_dev_size(store->cow->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_snap_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_fraction_full(struct dm_exception_store *store,
  63                                     sector_t *numerator, sector_t *denominator)
  64 {
  65         *numerator = ((struct transient_c *) store->context)->next_free;
  66         *denominator = get_dev_size(store->cow->bdev);
  67 }
  68
  69 static int transient_ctr(struct dm_exception_store *store,
  70                          unsigned argc, char **argv)
  71 {
  72         struct transient_c *tc;
  73
  74         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  75         if (!tc)
  76                 return -ENOMEM;
  77
  78         tc->next_free = 0;
  79         store->context = tc;
  80
  81         return 0;
  82 }
  83
  84 static unsigned transient_status(struct dm_exception_store *store,
  85                                  status_type_t status, char *result,
  86                                  unsigned maxlen)
  87 {
  88         unsigned sz = 0;
  89
  90         switch (status) {
  91         case STATUSTYPE_INFO:
  92                 break;
  93         case STATUSTYPE_TABLE:
  94                 DMEMIT(" %s N %llu", store->cow->name,
  95                        (unsigned long long)store->chunk_size);
  96         }
  97
  98         return sz;
  99 }
 100
 101 static struct dm_exception_store_type _transient_type = {
 102         .name = "transient",
 103         .module = THIS_MODULE,
 104         .ctr = transient_ctr,
 105         .dtr = transient_dtr,
 106         .read_metadata = transient_read_metadata,
 107         .prepare_exception = transient_prepare_exception,
 108         .commit_exception = transient_commit_exception,
 109         .fraction_full = transient_fraction_full,
 110         .status = transient_status,
 111 };
 112
 113 static struct dm_exception_store_type _transient_compat_type = {
 114         .name = "N",
 115         .module = THIS_MODULE,
 116         .ctr = transient_ctr,
 117         .dtr = transient_dtr,
 118         .read_metadata = transient_read_metadata,
 119         .prepare_exception = transient_prepare_exception,
 120         .commit_exception = transient_commit_exception,
 121         .fraction_full = transient_fraction_full,
 122         .status = transient_status,
 123 };
 124
 125 int dm_transient_snapshot_init(void)
 126 {
 127         int r;
 128
 129         r = dm_exception_store_type_register(&_transient_type);
 130         if (r) {
 131                 DMWARN("Unable to register transient exception store type");
 132                 return r;
 133         }
 134
 135         r = dm_exception_store_type_register(&_transient_compat_type);
 136         if (r) {
 137                 DMWARN("Unable to register old-style transient "
 138                        "exception store type");
 139                 dm_exception_store_type_unregister(&_transient_type);
 140                 return r;
 141         }
 142
 143         return r;
 144 }
 145
 146 void dm_transient_snapshot_exit(void)
 147 {
 148         dm_exception_store_type_unregister(&_transient_type);
 149         dm_exception_store_type_unregister(&_transient_compat_type);
 150 }