SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 #include "dm-snap.h"
  10
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/vmalloc.h>
  14 #include <linux/slab.h>
  15 #include <linux/dm-io.h>
  16
  17 #define DM_MSG_PREFIX "transient snapshot"
  18
  19 /*-----------------------------------------------------------------
  20  * Implementation of the store for non-persistent snapshots.
  21  *---------------------------------------------------------------*/
  22 struct transient_c {
  23         sector_t next_free;
  24 };
  25
  26 static void transient_dtr(struct dm_exception_store *store)
  27 {
  28         kfree(store->context);
  29 }
  30
  31 static int transient_read_metadata(struct dm_exception_store *store,
  32                                    int (*callback)(void *callback_context,
  33                                                    chunk_t old, chunk_t new),
  34                                    void *callback_context)
  35 {
  36         return 0;
  37 }
  38
  39 static int transient_prepare_exception(struct dm_exception_store *store,
  40                                        struct dm_snap_exception *e)
  41 {
  42         struct transient_c *tc = store->context;
  43         sector_t size = get_dev_size(store->snap->cow->bdev);
  44
  45         if (size < (tc->next_free + store->chunk_size))
  46                 return -1;
  47
  48         e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
  49         tc->next_free += store->chunk_size;
  50
  51         return 0;
  52 }
  53
  54 static void transient_commit_exception(struct dm_exception_store *store,
  55                                        struct dm_snap_exception *e,
  56                                        void (*callback) (void *, int success),
  57                                        void *callback_context)
  58 {
  59         /* Just succeed */
  60         callback(callback_context, 1);
  61 }
  62
  63 static void transient_fraction_full(struct dm_exception_store *store,
  64                                     sector_t *numerator, sector_t *denominator)
  65 {
  66         *numerator = ((struct transient_c *) store->context)->next_free;
  67         *denominator = get_dev_size(store->snap->cow->bdev);
  68 }
  69
  70 static int transient_ctr(struct dm_exception_store *store,
  71                          unsigned argc, char **argv)
  72 {
  73         struct transient_c *tc;
  74
  75         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  76         if (!tc)
  77                 return -ENOMEM;
  78
  79         tc->next_free = 0;
  80         store->context = tc;
  81
  82         return 0;
  83 }
  84
  85 static int transient_status(struct dm_exception_store *store,
  86                             status_type_t status, char *result,
  87                             unsigned maxlen)
  88 {
  89         int sz = 0;
  90
  91         return sz;
  92 }
  93
  94 static struct dm_exception_store_type _transient_type = {
  95         .name = "transient",
  96         .module = THIS_MODULE,
  97         .ctr = transient_ctr,
  98         .dtr = transient_dtr,
  99         .read_metadata = transient_read_metadata,
 100         .prepare_exception = transient_prepare_exception,
 101         .commit_exception = transient_commit_exception,
 102         .fraction_full = transient_fraction_full,
 103         .status = transient_status,
 104 };
 105
 106 static struct dm_exception_store_type _transient_compat_type = {
 107         .name = "N",
 108         .module = THIS_MODULE,
 109         .ctr = transient_ctr,
 110         .dtr = transient_dtr,
 111         .read_metadata = transient_read_metadata,
 112         .prepare_exception = transient_prepare_exception,
 113         .commit_exception = transient_commit_exception,
 114         .fraction_full = transient_fraction_full,
 115         .status = transient_status,
 116 };
 117
 118 int dm_transient_snapshot_init(void)
 119 {
 120         int r;
 121
 122         r = dm_exception_store_type_register(&_transient_type);
 123         if (r) {
 124                 DMWARN("Unable to register transient exception store type");
 125                 return r;
 126         }
 127
 128         r = dm_exception_store_type_register(&_transient_compat_type);
 129         if (r) {
 130                 DMWARN("Unable to register old-style transient "
 131                        "exception store type");
 132                 dm_exception_store_type_unregister(&_transient_type);
 133                 return r;
 134         }
 135
 136         return r;
 137 }
 138
 139 void dm_transient_snapshot_exit(void)
 140 {
 141         dm_exception_store_type_unregister(&_transient_type);
 142         dm_exception_store_type_unregister(&_transient_compat_type);
 143 }