text: /*
   * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
   * Copyright (C) 2006-2008 Red Hat GmbH
   *
   * This file is released under the GPL.
   */
  
  #include "dm-exception-store.h"
  
  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/vmalloc.h>
  #include <linux/slab.h>
  #include <linux/dm-io.h>
  
  #define DM_MSG_PREFIX "transient snapshot"
  
  /*-----------------------------------------------------------------
   * Implementation of the store for non-persistent snapshots.
   *---------------------------------------------------------------*/
  struct transient_c {
  	sector_t next_free;
  };
  
  static void transient_dtr(struct dm_exception_store *store)
  {
  	kfree(store->context);
  }
  
  static int transient_read_metadata(struct dm_exception_store *store,
  				   int (*callback)(void *callback_context,
  						   chunk_t old, chunk_t new),
  				   void *callback_context)
  {
  	return 0;
  }
  
  static int transient_prepare_exception(struct dm_exception_store *store,
  				       struct dm_snap_exception *e)
  {
  	struct transient_c *tc = store->context;
  	sector_t size = get_dev_size(store->cow->bdev);
  
  	if (size < (tc->next_free + store->chunk_size))
  		return -1;
  
  	e->new_chunk = sector_to_chunk(store, tc->next_free);
  	tc->next_free += store->chunk_size;
  
  	return 0;
  }
  
  static void transient_commit_exception(struct dm_exception_store *store,
  				       struct dm_snap_exception *e,
  				       void (*callback) (void *, int success),
  				       void *callback_context)
  {
  	/* Just succeed */
  	callback(callback_context, 1);
  }
  
  static void transient_fraction_full(struct dm_exception_store *store,
  				    sector_t *numerator, sector_t *denominator)
  {
  	*numerator = ((struct transient_c *) store->context)->next_free;
  	*denominator = get_dev_size(store->cow->bdev);
  }
  
  static int transient_ctr(struct dm_exception_store *store,
  			 unsigned argc, char **argv)
  {
  	struct transient_c *tc;
  
  	tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
  	if (!tc)
  		return -ENOMEM;
  
  	tc->next_free = 0;
  	store->context = tc;
  
  	return 0;
  }
  
  static unsigned transient_status(struct dm_exception_store *store,
  				 status_type_t status, char *result,
  				 unsigned maxlen)
  {
  	unsigned sz = 0;
  
  	switch (status) {
  	case STATUSTYPE_INFO:
  		break;
  	case STATUSTYPE_TABLE:
  		DMEMIT(" %s N %llu", store->cow->name,
  		       (unsigned long long)store->chunk_size);
  	}
  
  	return sz;
  }
  
  static struct dm_exception_store_type _transient_type = {
  	.name = "transient",
  	.module = THIS_MODULE,
  	.ctr = transient_ctr,
  	.dtr = transient_dtr,
  	.read_metadata = transient_read_metadata,
  	.prepare_exception = transient_prepare_exception,
  	.commit_exception = transient_commit_exception,
  	.fraction_full = transient_fraction_full,
  	.status = transient_status,
  };
  
  static struct dm_exception_store_type _transient_compat_type = {
  	.name = "N",
  	.module = THIS_MODULE,
  	.ctr = transient_ctr,
  	.dtr = transient_dtr,
  	.read_metadata = transient_read_metadata,
  	.prepare_exception = transient_prepare_exception,
  	.commit_exception = transient_commit_exception,
  	.fraction_full = transient_fraction_full,
  	.status = transient_status,
  };
  
  int dm_transient_snapshot_init(void)
  {
  	int r;
  
  	r = dm_exception_store_type_register(&_transient_type);
  	if (r) {
  		DMWARN("Unable to register transient exception store type");
  		return r;
  	}
  
  	r = dm_exception_store_type_register(&_transient_compat_type);
  	if (r) {
  		DMWARN("Unable to register old-style transient "
  		       "exception store type");
  		dm_exception_store_type_unregister(&_transient_type);
  		return r;
  	}
  
  	return r;
  }
  
  void dm_transient_snapshot_exit(void)
  {
  	dm_exception_store_type_unregister(&_transient_type);
  	dm_exception_store_type_unregister(&_transient_compat_type);
  }
  