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1/* SPDX-License-Identifier: GPL-2.0-only */2/*3 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.4 * Copyright (C) 2008 Red Hat, Inc. All rights reserved.5 *6 * Device-mapper snapshot exception store.7 *8 * This file is released under the GPL.9 */10 11#ifndef _LINUX_DM_EXCEPTION_STORE12#define _LINUX_DM_EXCEPTION_STORE13 14#include <linux/blkdev.h>15#include <linux/list_bl.h>16#include <linux/device-mapper.h>17 18/*19 * The snapshot code deals with largish chunks of the disk at a20 * time. Typically 32k - 512k.21 */22typedef sector_t chunk_t;23 24/*25 * An exception is used where an old chunk of data has been26 * replaced by a new one.27 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number28 * of chunks that follow contiguously. Remaining bits hold the number of the29 * chunk within the device.30 */31struct dm_exception {32 struct hlist_bl_node hash_list;33 34 chunk_t old_chunk;35 chunk_t new_chunk;36};37 38/*39 * Abstraction to handle the meta/layout of exception stores (the40 * COW device).41 */42struct dm_exception_store;43struct dm_exception_store_type {44 const char *name;45 struct module *module;46 47 int (*ctr)(struct dm_exception_store *store, char *options);48 49 /*50 * Destroys this object when you've finished with it.51 */52 void (*dtr)(struct dm_exception_store *store);53 54 /*55 * The target shouldn't read the COW device until this is56 * called. As exceptions are read from the COW, they are57 * reported back via the callback.58 */59 int (*read_metadata)(struct dm_exception_store *store,60 int (*callback)(void *callback_context,61 chunk_t old, chunk_t new),62 void *callback_context);63 64 /*65 * Find somewhere to store the next exception.66 */67 int (*prepare_exception)(struct dm_exception_store *store,68 struct dm_exception *e);69 70 /*71 * Update the metadata with this exception.72 */73 void (*commit_exception)(struct dm_exception_store *store,74 struct dm_exception *e, int valid,75 void (*callback)(void *, int success),76 void *callback_context);77 78 /*79 * Returns 0 if the exception store is empty.80 *81 * If there are exceptions still to be merged, sets82 * *last_old_chunk and *last_new_chunk to the most recent83 * still-to-be-merged chunk and returns the number of84 * consecutive previous ones.85 */86 int (*prepare_merge)(struct dm_exception_store *store,87 chunk_t *last_old_chunk, chunk_t *last_new_chunk);88 89 /*90 * Clear the last n exceptions.91 * nr_merged must be <= the value returned by prepare_merge.92 */93 int (*commit_merge)(struct dm_exception_store *store, int nr_merged);94 95 /*96 * The snapshot is invalid, note this in the metadata.97 */98 void (*drop_snapshot)(struct dm_exception_store *store);99 100 unsigned int (*status)(struct dm_exception_store *store,101 status_type_t status, char *result,102 unsigned int maxlen);103 104 /*105 * Return how full the snapshot is.106 */107 void (*usage)(struct dm_exception_store *store,108 sector_t *total_sectors, sector_t *sectors_allocated,109 sector_t *metadata_sectors);110 111 /* For internal device-mapper use only. */112 struct list_head list;113};114 115struct dm_snapshot;116 117struct dm_exception_store {118 struct dm_exception_store_type *type;119 struct dm_snapshot *snap;120 121 /* Size of data blocks saved - must be a power of 2 */122 unsigned int chunk_size;123 unsigned int chunk_mask;124 unsigned int chunk_shift;125 126 void *context;127 128 bool userspace_supports_overflow;129};130 131/*132 * Obtain the origin or cow device used by a given snapshot.133 */134struct dm_dev *dm_snap_origin(struct dm_snapshot *snap);135struct dm_dev *dm_snap_cow(struct dm_snapshot *snap);136 137/*138 * Funtions to manipulate consecutive chunks139 */140#define DM_CHUNK_CONSECUTIVE_BITS 8141#define DM_CHUNK_NUMBER_BITS 56142 143static inline chunk_t dm_chunk_number(chunk_t chunk)144{145 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);146}147 148static inline unsigned int dm_consecutive_chunk_count(struct dm_exception *e)149{150 return e->new_chunk >> DM_CHUNK_NUMBER_BITS;151}152 153static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e)154{155 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);156 157 BUG_ON(!dm_consecutive_chunk_count(e));158}159 160static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e)161{162 BUG_ON(!dm_consecutive_chunk_count(e));163 164 e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS);165}166 167/*168 * Return the number of sectors in the device.169 */170static inline sector_t get_dev_size(struct block_device *bdev)171{172 return bdev_nr_sectors(bdev);173}174 175static inline chunk_t sector_to_chunk(struct dm_exception_store *store,176 sector_t sector)177{178 return sector >> store->chunk_shift;179}180 181int dm_exception_store_type_register(struct dm_exception_store_type *type);182int dm_exception_store_type_unregister(struct dm_exception_store_type *type);183 184int dm_exception_store_set_chunk_size(struct dm_exception_store *store,185 unsigned int chunk_size,186 char **error);187 188int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,189 struct dm_snapshot *snap,190 unsigned int *args_used,191 struct dm_exception_store **store);192void dm_exception_store_destroy(struct dm_exception_store *store);193 194int dm_exception_store_init(void);195void dm_exception_store_exit(void);196 197/*198 * Two exception store implementations.199 */200int dm_persistent_snapshot_init(void);201void dm_persistent_snapshot_exit(void);202 203int dm_transient_snapshot_init(void);204void dm_transient_snapshot_exit(void);205 206#endif /* _LINUX_DM_EXCEPTION_STORE */207