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                                    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 = (struct transient_c *) store->context;
  43         sector_t size = get_dev_size(store->snap->cow->bdev);
  44
  45         if (size < (tc->next_free + store->snap->chunk_size))
  46                 return -1;
  47
  48         e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
  49         tc->next_free += store->snap->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 int dm_create_transient(struct dm_exception_store *store)
  71 {
  72         struct transient_c *tc;
  73
  74         store->destroy = transient_destroy;
  75         store->read_metadata = transient_read_metadata;
  76         store->prepare_exception = transient_prepare_exception;
  77         store->commit_exception = transient_commit_exception;
  78         store->drop_snapshot = NULL;
  79         store->fraction_full = transient_fraction_full;
  80
  81         tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  82         if (!tc)
  83                 return -ENOMEM;
  84
  85         tc->next_free = 0;
  86         store->context = tc;
  87
  88         return 0;
  89 }
  90
  91 int dm_transient_snapshot_init(void)
  92 {
  93         return 0;
  94 }
  95
  96 void dm_transient_snapshot_exit(void)
  97 {
  98 }