/* * dm-snapshot.c * * Copyright (C) 2001-2002 Sistina Software (UK) Limited. * * This file is released under the GPL. */ #ifndef DM_SNAPSHOT_H #define DM_SNAPSHOT_H #include <linux/device-mapper.h> #include "dm-bio-list.h" #include <linux/blkdev.h> #include <linux/workqueue.h> struct exception_table { uint32_t hash_mask; unsigned hash_shift; struct list_head *table; }; /* * The snapshot code deals with largish chunks of the disk at a * time. Typically 32k - 512k. */ typedef sector_t chunk_t; /* * An exception is used where an old chunk of data has been * replaced by a new one. * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number * of chunks that follow contiguously. Remaining bits hold the number of the * chunk within the device. */ struct dm_snap_exception { struct list_head hash_list; chunk_t old_chunk; chunk_t new_chunk; }; /* * Funtions to manipulate consecutive chunks */ # if defined(CONFIG_LBD) || (BITS_PER_LONG == 64) # define DM_CHUNK_CONSECUTIVE_BITS 8 # define DM_CHUNK_NUMBER_BITS 56 static inline chunk_t dm_chunk_number(chunk_t chunk) { return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); } static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) { return e->new_chunk >> DM_CHUNK_NUMBER_BITS; } static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) { e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); BUG_ON(!dm_consecutive_chunk_count(e)); } # else # define DM_CHUNK_CONSECUTIVE_BITS 0 static inline chunk_t dm_chunk_number(chunk_t chunk) { return chunk; } static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e) { return 0; } static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e) { } # endif /* * Abstraction to handle the meta/layout of exception stores (the * COW device). */ struct exception_store { /* * Destroys this object when you've finished with it. */ void (*destroy) (struct exception_store *store); /* * The target shouldn't read the COW device until this is * called. */ int (*read_metadata) (struct exception_store *store); /* * Find somewhere to store the next exception. */ int (*prepare_exception) (struct exception_store *store, struct dm_snap_exception *e); /* * Update the metadata with this exception. */ void (*commit_exception) (struct exception_store *store, struct dm_snap_exception *e, void (*callback) (void *, int success), void *callback_context); /* * The snapshot is invalid, note this in the metadata. */ void (*drop_snapshot) (struct exception_store *store); /* * Return how full the snapshot is. */ void (*fraction_full) (struct exception_store *store, sector_t *numerator, sector_t *denominator); struct dm_snapshot *snap; void *context; }; #define DM_TRACKED_CHUNK_HASH_SIZE 16 #define DM_TRACKED_CHUNK_HASH(x) ((unsigned long)(x) & \ (DM_TRACKED_CHUNK_HASH_SIZE - 1)) struct dm_snapshot { struct rw_semaphore lock; struct dm_target *ti; struct dm_dev *origin; struct dm_dev *cow; /* List of snapshots per Origin */ struct list_head list; /* Size of data blocks saved - must be a power of 2 */ chunk_t chunk_size; chunk_t chunk_mask; chunk_t chunk_shift; /* You can't use a snapshot if this is 0 (e.g. if full) */ int valid; /* Origin writes don't trigger exceptions until this is set */ int active; /* Used for display of table */ char type; mempool_t *pending_pool; atomic_t pending_exceptions_count; struct exception_table pending; struct exception_table complete; /* * pe_lock protects all pending_exception operations and access * as well as the snapshot_bios list. */ spinlock_t pe_lock; /* The on disk metadata handler */ struct exception_store store; struct dm_kcopyd_client *kcopyd_client; /* Queue of snapshot writes for ksnapd to flush */ struct bio_list queued_bios; struct work_struct queued_bios_work; /* Chunks with outstanding reads */ mempool_t *tracked_chunk_pool; spinlock_t tracked_chunk_lock; struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; }; /* * Used by the exception stores to load exceptions hen * initialising. */ int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new); /* * Constructor and destructor for the default persistent * store. */ int dm_create_persistent(struct exception_store *store); int dm_create_transient(struct exception_store *store); /* * Return the number of sectors in the device. */ static inline sector_t get_dev_size(struct block_device *bdev) { return bdev->bd_inode->i_size >> SECTOR_SHIFT; } static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector) { return (sector & ~s->chunk_mask) >> s->chunk_shift; } static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk) { return chunk << s->chunk_shift; } static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs) { /* * There is only ever one instance of a particular block * device so we can compare pointers safely. */ return lhs == rhs; } #endif