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/drivers/md/dm-exception-store.h

https://bitbucket.org/ndreys/linux-sunxi
C++ Header | 227 lines | 114 code | 44 blank | 69 comment | 3 complexity | 0e12d53f480ae27ad89817209acf2a92 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  1/*
  2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
  3 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
  4 *
  5 * Device-mapper snapshot exception store.
  6 *
  7 * This file is released under the GPL.
  8 */
  9
 10#ifndef _LINUX_DM_EXCEPTION_STORE
 11#define _LINUX_DM_EXCEPTION_STORE
 12
 13#include <linux/blkdev.h>
 14#include <linux/device-mapper.h>
 15
 16/*
 17 * The snapshot code deals with largish chunks of the disk at a
 18 * time. Typically 32k - 512k.
 19 */
 20typedef sector_t chunk_t;
 21
 22/*
 23 * An exception is used where an old chunk of data has been
 24 * replaced by a new one.
 25 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
 26 * of chunks that follow contiguously.  Remaining bits hold the number of the
 27 * chunk within the device.
 28 */
 29struct dm_exception {
 30	struct list_head hash_list;
 31
 32	chunk_t old_chunk;
 33	chunk_t new_chunk;
 34};
 35
 36/*
 37 * Abstraction to handle the meta/layout of exception stores (the
 38 * COW device).
 39 */
 40struct dm_exception_store;
 41struct dm_exception_store_type {
 42	const char *name;
 43	struct module *module;
 44
 45	int (*ctr) (struct dm_exception_store *store,
 46		    unsigned argc, char **argv);
 47
 48	/*
 49	 * Destroys this object when you've finished with it.
 50	 */
 51	void (*dtr) (struct dm_exception_store *store);
 52
 53	/*
 54	 * The target shouldn't read the COW device until this is
 55	 * called.  As exceptions are read from the COW, they are
 56	 * reported back via the callback.
 57	 */
 58	int (*read_metadata) (struct dm_exception_store *store,
 59			      int (*callback)(void *callback_context,
 60					      chunk_t old, chunk_t new),
 61			      void *callback_context);
 62
 63	/*
 64	 * Find somewhere to store the next exception.
 65	 */
 66	int (*prepare_exception) (struct dm_exception_store *store,
 67				  struct dm_exception *e);
 68
 69	/*
 70	 * Update the metadata with this exception.
 71	 */
 72	void (*commit_exception) (struct dm_exception_store *store,
 73				  struct dm_exception *e,
 74				  void (*callback) (void *, int success),
 75				  void *callback_context);
 76
 77	/*
 78	 * Returns 0 if the exception store is empty.
 79	 *
 80	 * If there are exceptions still to be merged, sets
 81	 * *last_old_chunk and *last_new_chunk to the most recent
 82	 * still-to-be-merged chunk and returns the number of
 83	 * consecutive previous ones.
 84	 */
 85	int (*prepare_merge) (struct dm_exception_store *store,
 86			      chunk_t *last_old_chunk, chunk_t *last_new_chunk);
 87
 88	/*
 89	 * Clear the last n exceptions.
 90	 * nr_merged must be <= the value returned by prepare_merge.
 91	 */
 92	int (*commit_merge) (struct dm_exception_store *store, int nr_merged);
 93
 94	/*
 95	 * The snapshot is invalid, note this in the metadata.
 96	 */
 97	void (*drop_snapshot) (struct dm_exception_store *store);
 98
 99	unsigned (*status) (struct dm_exception_store *store,
100			    status_type_t status, char *result,
101			    unsigned maxlen);
102
103	/*
104	 * Return how full the snapshot is.
105	 */
106	void (*usage) (struct dm_exception_store *store,
107		       sector_t *total_sectors, sector_t *sectors_allocated,
108		       sector_t *metadata_sectors);
109
110	/* For internal device-mapper use only. */
111	struct list_head list;
112};
113
114struct dm_snapshot;
115
116struct dm_exception_store {
117	struct dm_exception_store_type *type;
118	struct dm_snapshot *snap;
119
120	/* Size of data blocks saved - must be a power of 2 */
121	unsigned chunk_size;
122	unsigned chunk_mask;
123	unsigned chunk_shift;
124
125	void *context;
126};
127
128/*
129 * Obtain the origin or cow device used by a given snapshot.
130 */
131struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);
132struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);
133
134/*
135 * Funtions to manipulate consecutive chunks
136 */
137#  if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64)
138#    define DM_CHUNK_CONSECUTIVE_BITS 8
139#    define DM_CHUNK_NUMBER_BITS 56
140
141static inline chunk_t dm_chunk_number(chunk_t chunk)
142{
143	return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
144}
145
146static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
147{
148	return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
149}
150
151static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
152{
153	e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
154
155	BUG_ON(!dm_consecutive_chunk_count(e));
156}
157
158static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
159{
160	BUG_ON(!dm_consecutive_chunk_count(e));
161
162	e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);
163}
164
165#  else
166#    define DM_CHUNK_CONSECUTIVE_BITS 0
167
168static inline chunk_t dm_chunk_number(chunk_t chunk)
169{
170	return chunk;
171}
172
173static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e)
174{
175	return 0;
176}
177
178static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)
179{
180}
181
182static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)
183{
184}
185
186#  endif
187
188/*
189 * Return the number of sectors in the device.
190 */
191static inline sector_t get_dev_size(struct block_device *bdev)
192{
193	return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
194}
195
196static inline chunk_t sector_to_chunk(struct dm_exception_store *store,
197				      sector_t sector)
198{
199	return sector >> store->chunk_shift;
200}
201
202int dm_exception_store_type_register(struct dm_exception_store_type *type);
203int dm_exception_store_type_unregister(struct dm_exception_store_type *type);
204
205int dm_exception_store_set_chunk_size(struct dm_exception_store *store,
206				      unsigned chunk_size,
207				      char **error);
208
209int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,
210			      struct dm_snapshot *snap,
211			      unsigned *args_used,
212			      struct dm_exception_store **store);
213void dm_exception_store_destroy(struct dm_exception_store *store);
214
215int dm_exception_store_init(void);
216void dm_exception_store_exit(void);
217
218/*
219 * Two exception store implementations.
220 */
221int dm_persistent_snapshot_init(void);
222void dm_persistent_snapshot_exit(void);
223
224int dm_transient_snapshot_init(void);
225void dm_transient_snapshot_exit(void);
226
227#endif /* _LINUX_DM_EXCEPTION_STORE */