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 	int (*flush_callback_fn)(struct dm_target *ti);
25 	void *context;
26 };
27 
28 struct dm_dirty_log_type {
29 	const char *name;
30 	struct module *module;
31 
32 	/* For internal device-mapper use */
33 	struct list_head list;
34 
35 	int (*ctr)(struct dm_dirty_log *log, struct dm_target *ti,
36 		   unsigned argc, char **argv);
37 	void (*dtr)(struct dm_dirty_log *log);
38 
39 	/*
40 	 * There are times when we don't want the log to touch
41 	 * the disk.
42 	 */
43 	int (*presuspend)(struct dm_dirty_log *log);
44 	int (*postsuspend)(struct dm_dirty_log *log);
45 	int (*resume)(struct dm_dirty_log *log);
46 
47 	/*
48 	 * Retrieves the smallest size of region that the log can
49 	 * deal with.
50 	 */
51 	uint32_t (*get_region_size)(struct dm_dirty_log *log);
52 
53 	/*
54 	 * A predicate to say whether a region is clean or not.
55 	 * May block.
56 	 */
57 	int (*is_clean)(struct dm_dirty_log *log, region_t region);
58 
59 	/*
60 	 *  Returns: 0, 1, -EWOULDBLOCK, < 0
61 	 *
62 	 * A predicate function to check the area given by
63 	 * [sector, sector + len) is in sync.
64 	 *
65 	 * If -EWOULDBLOCK is returned the state of the region is
66 	 * unknown, typically this will result in a read being
67 	 * passed to a daemon to deal with, since a daemon is
68 	 * allowed to block.
69 	 */
70 	int (*in_sync)(struct dm_dirty_log *log, region_t region,
71 		       int can_block);
72 
73 	/*
74 	 * Flush the current log state (eg, to disk).  This
75 	 * function may block.
76 	 */
77 	int (*flush)(struct dm_dirty_log *log);
78 
79 	/*
80 	 * Mark an area as clean or dirty.  These functions may
81 	 * block, though for performance reasons blocking should
82 	 * be extremely rare (eg, allocating another chunk of
83 	 * memory for some reason).
84 	 */
85 	void (*mark_region)(struct dm_dirty_log *log, region_t region);
86 	void (*clear_region)(struct dm_dirty_log *log, region_t region);
87 
88 	/*
89 	 * Returns: <0 (error), 0 (no region), 1 (region)
90 	 *
91 	 * The mirrord will need perform recovery on regions of
92 	 * the mirror that are in the NOSYNC state.  This
93 	 * function asks the log to tell the caller about the
94 	 * next region that this machine should recover.
95 	 *
96 	 * Do not confuse this function with 'in_sync()', one
97 	 * tells you if an area is synchronised, the other
98 	 * assigns recovery work.
99 	*/
100 	int (*get_resync_work)(struct dm_dirty_log *log, region_t *region);
101 
102 	/*
103 	 * This notifies the log that the resync status of a region
104 	 * has changed.  It also clears the region from the recovering
105 	 * list (if present).
106 	 */
107 	void (*set_region_sync)(struct dm_dirty_log *log,
108 				region_t region, int in_sync);
109 
110 	/*
111 	 * Returns the number of regions that are in sync.
112 	 */
113 	region_t (*get_sync_count)(struct dm_dirty_log *log);
114 
115 	/*
116 	 * Support function for mirror status requests.
117 	 */
118 	int (*status)(struct dm_dirty_log *log, status_type_t status_type,
119 		      char *result, unsigned maxlen);
120 
121 	/*
122 	 * is_remote_recovering is necessary for cluster mirroring. It provides
123 	 * a way to detect recovery on another node, so we aren't writing
124 	 * concurrently.  This function is likely to block (when a cluster log
125 	 * is used).
126 	 *
127 	 * Returns: 0, 1
128 	 */
129 	int (*is_remote_recovering)(struct dm_dirty_log *log, region_t region);
130 };
131 
132 int dm_dirty_log_type_register(struct dm_dirty_log_type *type);
133 int dm_dirty_log_type_unregister(struct dm_dirty_log_type *type);
134 
135 /*
136  * Make sure you use these two functions, rather than calling
137  * type->constructor/destructor() directly.
138  */
139 struct dm_dirty_log *dm_dirty_log_create(const char *type_name,
140 			struct dm_target *ti,
141 			int (*flush_callback_fn)(struct dm_target *ti),
142 			unsigned argc, char **argv);
143 void dm_dirty_log_destroy(struct dm_dirty_log *log);
144 
145 #endif	/* __KERNEL__ */
146 #endif	/* _LINUX_DM_DIRTY_LOG_H */
147