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_destroy(struct dm_exception_store *store)
  27 {
  28         kfree(store->context);
  29 }
  30
  31 static int transient_read_metadata(struct dm_exception_store *store)
  32 {
  33         return 0;
  34 }
  35
  36 static int transient_prepare(struct dm_exception_store *store,
  37                              struct dm_snap_exception *e)
  38 {
  39         struct transient_c *tc = (struct transient_c *) store->context;
  40         sector_t size = get_dev_size(store->snap->cow->bdev);
  41
  42         if (size < (tc->next_free + store->snap->chunk_size))
  43                 return -1;
  44
  45         e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
  46         tc->next_free += store->snap->chunk_size;
  47
  48         return 0;
  49 }
  50
  51 static void transient_commit(struct dm_exception_store *store,
  52                              struct dm_snap_exception *e,
  53                              void (*callback) (void *, int success),
  54                              void *callback_context)
  55 {
  56         /* Just succeed */
  57         callback(callback_context, 1);
  58 }
  59
  60 static void transient_fraction_full(struct dm_exception_store *store,
  61                                     sector_t *numerator, sector_t *denominator)
  62 {
  63         *numerator = ((struct transient_c *) store->context)->next_free;
  64         *denominator = get_dev_size(store->snap->cow->bdev);
  65 }
  66
  67 int dm_create_transient(struct dm_exception_store *store)
  68 {
  69         struct transient_c *tc;
  70
  71         store->destroy = transient_destroy;
  72         store->read_metadata = transient_read_metadata;
  73         store->prepare_exception = transient_prepare;
  74         store->commit_exception = transient_commit;
  75         store->drop_snapshot = NULL;
  76         store->fraction_full = transient_fraction_full;
  77
  78         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  79         if (!tc)
  80                 return -ENOMEM;
  81
  82         tc->next_free = 0;
  83         store->context = tc;
  84
  85         return 0;
  86 }
  87
  88 int dm_transient_snapshot_init(void)
  89 {
  90         return 0;
  91 }
  92
  93 void dm_transient_snapshot_exit(void)
  94 {
  95 }