text: /*
   * Copyright (C) 2012 Red Hat, Inc.
   *
   * This file is released under the GPL.
   */
  
  #ifndef DM_CACHE_METADATA_H
  #define DM_CACHE_METADATA_H
  
  #include "dm-cache-block-types.h"
  #include "dm-cache-policy-internal.h"
  
  /*----------------------------------------------------------------*/
  
  #define DM_CACHE_METADATA_BLOCK_SIZE 4096
  
  /* FIXME: remove this restriction */
  /*
   * The metadata device is currently limited in size.
   *
   * We have one block of index, which can hold 255 index entries.  Each
   * index entry contains allocation info about 16k metadata blocks.
   */
  #define DM_CACHE_METADATA_MAX_SECTORS (255 * (1 << 14) * (DM_CACHE_METADATA_BLOCK_SIZE / (1 << SECTOR_SHIFT)))
  
  /*
   * A metadata device larger than 16GB triggers a warning.
   */
  #define DM_CACHE_METADATA_MAX_SECTORS_WARNING (16 * (1024 * 1024 * 1024 >> SECTOR_SHIFT))
  
  /*----------------------------------------------------------------*/
  
  /*
   * Ext[234]-style compat feature flags.
   *
   * A new feature which old metadata will still be compatible with should
   * define a DM_CACHE_FEATURE_COMPAT_* flag (rarely useful).
   *
   * A new feature that is not compatible with old code should define a
   * DM_CACHE_FEATURE_INCOMPAT_* flag and guard the relevant code with
   * that flag.
   *
   * A new feature that is not compatible with old code accessing the
   * metadata RDWR should define a DM_CACHE_FEATURE_RO_COMPAT_* flag and
   * guard the relevant code with that flag.
   *
   * As these various flags are defined they should be added to the
   * following masks.
   */
  #define DM_CACHE_FEATURE_COMPAT_SUPP	  0UL
  #define DM_CACHE_FEATURE_COMPAT_RO_SUPP	  0UL
  #define DM_CACHE_FEATURE_INCOMPAT_SUPP	  0UL
  
  /*
   * Reopens or creates a new, empty metadata volume.
   * Returns an ERR_PTR on failure.
   */
  struct dm_cache_metadata *dm_cache_metadata_open(struct block_device *bdev,
  						 sector_t data_block_size,
  						 bool may_format_device,
  						 size_t policy_hint_size);
  
  void dm_cache_metadata_close(struct dm_cache_metadata *cmd);
  
  /*
   * The metadata needs to know how many cache blocks there are.  We don't
   * care about the origin, assuming the core target is giving us valid
   * origin blocks to map to.
   */
  int dm_cache_resize(struct dm_cache_metadata *cmd, dm_cblock_t new_cache_size);
  dm_cblock_t dm_cache_size(struct dm_cache_metadata *cmd);
  
  int dm_cache_discard_bitset_resize(struct dm_cache_metadata *cmd,
  				   sector_t discard_block_size,
  				   dm_dblock_t new_nr_entries);
  
  typedef int (*load_discard_fn)(void *context, sector_t discard_block_size,
  			       dm_dblock_t dblock, bool discarded);
  int dm_cache_load_discards(struct dm_cache_metadata *cmd,
  			   load_discard_fn fn, void *context);
  
  int dm_cache_set_discard(struct dm_cache_metadata *cmd, dm_dblock_t dblock, bool discard);
  
  int dm_cache_remove_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock);
  int dm_cache_insert_mapping(struct dm_cache_metadata *cmd, dm_cblock_t cblock, dm_oblock_t oblock);
  int dm_cache_changed_this_transaction(struct dm_cache_metadata *cmd);
  
  typedef int (*load_mapping_fn)(void *context, dm_oblock_t oblock,
  			       dm_cblock_t cblock, bool dirty,
  			       uint32_t hint, bool hint_valid);
  int dm_cache_load_mappings(struct dm_cache_metadata *cmd,
  			   struct dm_cache_policy *policy,
  			   load_mapping_fn fn,
  			   void *context);
  
  int dm_cache_set_dirty(struct dm_cache_metadata *cmd, dm_cblock_t cblock, bool dirty);
  
  struct dm_cache_statistics {
  	uint32_t read_hits;
  	uint32_t read_misses;
  	uint32_t write_hits;
  	uint32_t write_misses;
  };
  
  void dm_cache_metadata_get_stats(struct dm_cache_metadata *cmd,
  				 struct dm_cache_statistics *stats);
  void dm_cache_metadata_set_stats(struct dm_cache_metadata *cmd,
  				 struct dm_cache_statistics *stats);
  
  int dm_cache_commit(struct dm_cache_metadata *cmd, bool clean_shutdown);
  
  int dm_cache_get_free_metadata_block_count(struct dm_cache_metadata *cmd,
  					   dm_block_t *result);
  
  int dm_cache_get_metadata_dev_size(struct dm_cache_metadata *cmd,
  				   dm_block_t *result);
  
  void dm_cache_dump(struct dm_cache_metadata *cmd);
  
  /*
   * The policy is invited to save a 32bit hint value for every cblock (eg,
   * for a hit count).  These are stored against the policy name.  If
   * policies are changed, then hints will be lost.  If the machine crashes,
   * hints will be lost.
   *
   * The hints are indexed by the cblock, but many policies will not
   * neccessarily have a fast way of accessing efficiently via cblock.  So
   * rather than querying the policy for each cblock, we let it walk its data
   * structures and fill in the hints in whatever order it wishes.
   */
  
  int dm_cache_begin_hints(struct dm_cache_metadata *cmd, struct dm_cache_policy *p);
  
  /*
   * requests hints for every cblock and stores in the metadata device.
   */
  int dm_cache_save_hint(struct dm_cache_metadata *cmd,
  		       dm_cblock_t cblock, uint32_t hint);
  
  /*
   * Query method.  Are all the blocks in the cache clean?
   */
  int dm_cache_metadata_all_clean(struct dm_cache_metadata *cmd, bool *result);
  
  /*----------------------------------------------------------------*/
  
  #endif /* DM_CACHE_METADATA_H */
  