root/include/linux/dm-dirty-log.h

/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * Device-Mapper dirty region log.
 *
 * This file is released under the LGPL.
 */

#ifndef _LINUX_DM_DIRTY_LOG
#define _LINUX_DM_DIRTY_LOG

#ifdef __KERNEL__

#include <linux/types.h>
#include <linux/device-mapper.h>

typedef sector_t region_t;

struct dm_dirty_log_type;

struct dm_dirty_log {
        struct dm_dirty_log_type *type;
        void *context;
};

struct dm_dirty_log_type {
        const char *name;
        struct module *module;

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

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

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

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

        /*
         * Flush the current log state (eg, to disk).  This
         * function may block.
         */
        int (*flush)(struct dm_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 dm_dirty_log *log, region_t region);
        void (*clear_region)(struct dm_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 dm_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 dm_dirty_log *log,
                                region_t region, int in_sync);

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

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

int dm_dirty_log_type_register(struct dm_dirty_log_type *type);
int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type);

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

#endif  /* __KERNEL__ */
#endif  /* _LINUX_DM_DIRTY_LOG_H */