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 int transient_status(struct dm_exception_store *store,
  85                             status_type_t status, char *result,
  86                             unsigned maxlen)
  87 {
  88         int sz = 0;
  89
  90         return sz;
  91 }
  92
  93 static struct dm_exception_store_type _transient_type = {
  94         .name = "transient",
  95         .module = THIS_MODULE,
  96         .ctr = transient_ctr,
  97         .dtr = transient_dtr,
  98         .read_metadata = transient_read_metadata,
  99         .prepare_exception = transient_prepare_exception,
 100         .commit_exception = transient_commit_exception,
 101         .fraction_full = transient_fraction_full,
 102         .status = transient_status,
 103 };
 104
 105 static struct dm_exception_store_type _transient_compat_type = {
 106         .name = "N",
 107         .module = THIS_MODULE,
 108         .ctr = transient_ctr,
 109         .dtr = transient_dtr,
 110         .read_metadata = transient_read_metadata,
 111         .prepare_exception = transient_prepare_exception,
 112         .commit_exception = transient_commit_exception,
 113         .fraction_full = transient_fraction_full,
 114         .status = transient_status,
 115 };
 116
 117 int dm_transient_snapshot_init(void)
 118 {
 119         int r;
 120
 121         r = dm_exception_store_type_register(&_transient_type);
 122         if (r) {
 123                 DMWARN("Unable to register transient exception store type");
 124                 return r;
 125         }
 126
 127         r = dm_exception_store_type_register(&_transient_compat_type);
 128         if (r) {
 129                 DMWARN("Unable to register old-style transient "
 130                        "exception store type");
 131                 dm_exception_store_type_unregister(&_transient_type);
 132                 return r;
 133         }
 134
 135         return r;
 136 }
 137
 138 void dm_transient_snapshot_exit(void)
 139 {
 140         dm_exception_store_type_unregister(&_transient_type);
 141         dm_exception_store_type_unregister(&_transient_compat_type);
 142 }