linux/drivers/md/dm-snap-transient.c
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   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/export.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 *---------------------------------------------------------------*/
  22struct transient_c {
  23        sector_t next_free;
  24};
  25
  26static void transient_dtr(struct dm_exception_store *store)
  27{
  28        kfree(store->context);
  29}
  30
  31static 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
  39static int transient_prepare_exception(struct dm_exception_store *store,
  40                                       struct dm_exception *e)
  41{
  42        struct transient_c *tc = store->context;
  43        sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
  44
  45        if (size < (tc->next_free + store->chunk_size))
  46                return -1;
  47
  48        e->new_chunk = sector_to_chunk(store, tc->next_free);
  49        tc->next_free += store->chunk_size;
  50
  51        return 0;
  52}
  53
  54static void transient_commit_exception(struct dm_exception_store *store,
  55                                       struct dm_exception *e,
  56                                       void (*callback) (void *, int success),
  57                                       void *callback_context)
  58{
  59        /* Just succeed */
  60        callback(callback_context, 1);
  61}
  62
  63static void transient_usage(struct dm_exception_store *store,
  64                            sector_t *total_sectors,
  65                            sector_t *sectors_allocated,
  66                            sector_t *metadata_sectors)
  67{
  68        *sectors_allocated = ((struct transient_c *) store->context)->next_free;
  69        *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
  70        *metadata_sectors = 0;
  71}
  72
  73static int transient_ctr(struct dm_exception_store *store,
  74                         unsigned argc, char **argv)
  75{
  76        struct transient_c *tc;
  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
  88static unsigned transient_status(struct dm_exception_store *store,
  89                                 status_type_t status, char *result,
  90                                 unsigned maxlen)
  91{
  92        unsigned sz = 0;
  93
  94        switch (status) {
  95        case STATUSTYPE_INFO:
  96                break;
  97        case STATUSTYPE_TABLE:
  98                DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
  99        }
 100
 101        return sz;
 102}
 103
 104static struct dm_exception_store_type _transient_type = {
 105        .name = "transient",
 106        .module = THIS_MODULE,
 107        .ctr = transient_ctr,
 108        .dtr = transient_dtr,
 109        .read_metadata = transient_read_metadata,
 110        .prepare_exception = transient_prepare_exception,
 111        .commit_exception = transient_commit_exception,
 112        .usage = transient_usage,
 113        .status = transient_status,
 114};
 115
 116static struct dm_exception_store_type _transient_compat_type = {
 117        .name = "N",
 118        .module = THIS_MODULE,
 119        .ctr = transient_ctr,
 120        .dtr = transient_dtr,
 121        .read_metadata = transient_read_metadata,
 122        .prepare_exception = transient_prepare_exception,
 123        .commit_exception = transient_commit_exception,
 124        .usage = transient_usage,
 125        .status = transient_status,
 126};
 127
 128int dm_transient_snapshot_init(void)
 129{
 130        int r;
 131
 132        r = dm_exception_store_type_register(&_transient_type);
 133        if (r) {
 134                DMWARN("Unable to register transient exception store type");
 135                return r;
 136        }
 137
 138        r = dm_exception_store_type_register(&_transient_compat_type);
 139        if (r) {
 140                DMWARN("Unable to register old-style transient "
 141                       "exception store type");
 142                dm_exception_store_type_unregister(&_transient_type);
 143                return r;
 144        }
 145
 146        return r;
 147}
 148
 149void dm_transient_snapshot_exit(void)
 150{
 151        dm_exception_store_type_unregister(&_transient_type);
 152        dm_exception_store_type_unregister(&_transient_compat_type);
 153}
 154
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