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dm-log.h

/*
 * Copyright (C) 2003 Sistina Software
 *
 * This file is released under the LGPL.
 */

#ifndef DM_DIRTY_LOG
#define DM_DIRTY_LOG

#include "dm.h"

typedef sector_t region_t;

struct dirty_log_type;

struct dirty_log {
      struct dirty_log_type *type;
      void *context;
};

struct dirty_log_type {
      struct list_head list;
      const char *name;
      struct module *module;
      unsigned int use_count;

      int (*ctr)(struct dirty_log *log, struct dm_target *ti,
               unsigned int argc, char **argv);
      void (*dtr)(struct dirty_log *log);

      /*
       * There are times when we don't want the log to touch
       * the disk.
       */
      int (*presuspend)(struct dirty_log *log);
      int (*postsuspend)(struct dirty_log *log);
      int (*resume)(struct dirty_log *log);

      /*
       * Retrieves the smallest size of region that the log can
       * deal with.
       */
      uint32_t (*get_region_size)(struct dirty_log *log);

        /*
       * A predicate to say whether a region is clean or not.
       * May block.
       */
      int (*is_clean)(struct dirty_log *log, region_t region);

      /*
       *  Returns: 0, 1, -EWOULDBLOCK, < 0
       *
       * A predicate function to check the area given by
       * [sector, sector + len) is in sync.
       *
       * If -EWOULDBLOCK is returned the state of the region is
       * unknown, typically this will result in a read being
       * passed to a daemon to deal with, since a daemon is
       * allowed to block.
       */
      int (*in_sync)(struct dirty_log *log, region_t region, int can_block);

      /*
       * Flush the current log state (eg, to disk).  This
       * function may block.
       */
      int (*flush)(struct dirty_log *log);

      /*
       * Mark an area as clean or dirty.  These functions may
       * block, though for performance reasons blocking should
       * be extremely rare (eg, allocating another chunk of
       * memory for some reason).
       */
      void (*mark_region)(struct dirty_log *log, region_t region);
      void (*clear_region)(struct dirty_log *log, region_t region);

      /*
       * Returns: <0 (error), 0 (no region), 1 (region)
       *
       * The mirrord will need perform recovery on regions of
       * the mirror that are in the NOSYNC state.  This
       * function asks the log to tell the caller about the
       * next region that this machine should recover.
       *
       * Do not confuse this function with 'in_sync()', one
       * tells you if an area is synchronised, the other
       * assigns recovery work.
      */
      int (*get_resync_work)(struct dirty_log *log, region_t *region);

      /*
       * This notifies the log that the resync status of a region
       * has changed.  It also clears the region from the recovering
       * list (if present).
       */
      void (*set_region_sync)(struct dirty_log *log,
                        region_t region, int in_sync);

        /*
       * Returns the number of regions that are in sync.
         */
        region_t (*get_sync_count)(struct dirty_log *log);

      /*
       * Support function for mirror status requests.
       */
      int (*status)(struct dirty_log *log, status_type_t status_type,
                  char *result, unsigned int maxlen);
};

int dm_register_dirty_log_type(struct dirty_log_type *type);
int dm_unregister_dirty_log_type(struct dirty_log_type *type);


/*
 * Make sure you use these two functions, rather than calling
 * type->constructor/destructor() directly.
 */
struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
                              unsigned int argc, char **argv);
void dm_destroy_dirty_log(struct dirty_log *log);

/*
 * init/exit functions.
 */
int dm_dirty_log_init(void);
void dm_dirty_log_exit(void);

#endif

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