include/linux/dm-dirty-log.h

   1 /*
   2  * Copyright (C) 2003 Sistina Software
   3  * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
   4  *
   5  * Device-Mapper dirty region log.
   6  *
   7  * This file is released under the LGPL.
   8  */
   9
  10 #ifndef _LINUX_DM_DIRTY_LOG
  11 #define _LINUX_DM_DIRTY_LOG
  12
  13 #ifdef __KERNEL__
  14
  15 #include <linux/types.h>
  16 #include <linux/device-mapper.h>
  17
  18 typedef sector_t region_t;
  19
  20 struct dm_dirty_log_type;
  21
  22 struct dm_dirty_log {
  23         struct dm_dirty_log_type *type;
  24         void *context;
  25 };
  26
  27 struct dm_dirty_log_type {
  28         const char *name;
  29         struct module *module;
  30
  31         /* For internal device-mapper use */
  32         struct list_head list;
  33
  34         int (*ctr)(struct dm_dirty_log *log, struct dm_target *ti,
  35                    unsigned argc, char **argv);
  36         void (*dtr)(struct dm_dirty_log *log);
  37
  38         /*
  39          * There are times when we don't want the log to touch
  40          * the disk.
  41          */
  42         int (*presuspend)(struct dm_dirty_log *log);
  43         int (*postsuspend)(struct dm_dirty_log *log);
  44         int (*resume)(struct dm_dirty_log *log);
  45
  46         /*
  47          * Retrieves the smallest size of region that the log can
  48          * deal with.
  49          */
  50         uint32_t (*get_region_size)(struct dm_dirty_log *log);
  51
  52         /*
  53          * A predicate to say whether a region is clean or not.
  54          * May block.
  55          */
  56         int (*is_clean)(struct dm_dirty_log *log, region_t region);
  57
  58         /*
  59          *  Returns: 0, 1, -EWOULDBLOCK, < 0
  60          *
  61          * A predicate function to check the area given by
  62          * [sector, sector + len) is in sync.
  63          *
  64          * If -EWOULDBLOCK is returned the state of the region is
  65          * unknown, typically this will result in a read being
  66          * passed to a daemon to deal with, since a daemon is
  67          * allowed to block.
  68          */
  69         int (*in_sync)(struct dm_dirty_log *log, region_t region,
  70                        int can_block);
  71
  72         /*
  73          * Flush the current log state (eg, to disk).  This
  74          * function may block.
  75          */
  76         int (*flush)(struct dm_dirty_log *log);
  77
  78         /*
  79          * Mark an area as clean or dirty.  These functions may
  80          * block, though for performance reasons blocking should
  81          * be extremely rare (eg, allocating another chunk of
  82          * memory for some reason).
  83          */
  84         void (*mark_region)(struct dm_dirty_log *log, region_t region);
  85         void (*clear_region)(struct dm_dirty_log *log, region_t region);
  86
  87         /*
  88          * Returns: <0 (error), 0 (no region), 1 (region)
  89          *
  90          * The mirrord will need perform recovery on regions of
  91          * the mirror that are in the NOSYNC state.  This
  92          * function asks the log to tell the caller about the
  93          * next region that this machine should recover.
  94          *
  95          * Do not confuse this function with 'in_sync()', one
  96          * tells you if an area is synchronised, the other
  97          * assigns recovery work.
  98         */
  99         int (*get_resync_work)(struct dm_dirty_log *log, region_t *region);
 100
 101         /*
 102          * This notifies the log that the resync status of a region
 103          * has changed.  It also clears the region from the recovering
 104          * list (if present).
 105          */
 106         void (*set_region_sync)(struct dm_dirty_log *log,
 107                                 region_t region, int in_sync);
 108
 109         /*
 110          * Returns the number of regions that are in sync.
 111          */
 112         region_t (*get_sync_count)(struct dm_dirty_log *log);
 113
 114         /*
 115          * Support function for mirror status requests.
 116          */
 117         int (*status)(struct dm_dirty_log *log, status_type_t status_type,
 118                       char *result, unsigned maxlen);
 119
 120         /*
 121          * is_remote_recovering is necessary for cluster mirroring. It provides
 122          * a way to detect recovery on another node, so we aren't writing
 123          * concurrently.  This function is likely to block (when a cluster log
 124          * is used).
 125          *
 126          * Returns: 0, 1
 127          */
 128         int (*is_remote_recovering)(struct dm_dirty_log *log, region_t region);
 129 };
 130
 131 int dm_dirty_log_type_register(struct dm_dirty_log_type *type);
 132 int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type);
 133
 134 /*
 135  * Make sure you use these two functions, rather than calling
 136  * type->constructor/destructor() directly.
 137  */
 138 struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
 139                                          struct dm_target *ti,
 140                                          unsigned argc, char **argv);
 141 void dm_dirty_log_destroy(struct dm_dirty_log *log);
 142
 143 #endif  /* __KERNEL__ */
 144 #endif  /* _LINUX_DM_DIRTY_LOG_H */