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/*
* Copyright (C) 2012 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#ifndef _LINUX_DM_BITSET_H
#define _LINUX_DM_BITSET_H
#include "dm-array.h"
/*----------------------------------------------------------------*/
/*
* This bitset type is a thin wrapper round a dm_array of 64bit words. It
* uses a tiny, one word cache to reduce the number of array lookups and so
* increase performance.
*
* Like the dm-array that it's based on, the caller needs to keep track of
* the size of the bitset separately. The underlying dm-array implicitly
* knows how many words it's storing and will return -ENODATA if you try
* and access an out of bounds word. However, an out of bounds bit in the
* final word will _not_ be detected, you have been warned.
*
* Bits are indexed from zero.
* Typical use:
*
* a) Initialise a dm_disk_bitset structure with dm_disk_bitset_init().
* This describes the bitset and includes the cache. It's not called it
* dm_bitset_info in line with other data structures because it does
* include instance data.
*
* b) Get yourself a root. The root is the index of a block of data on the
* disk that holds a particular instance of an bitset. You may have a
* pre existing root in your metadata that you wish to use, or you may
* want to create a brand new, empty bitset with dm_bitset_empty().
*
* Like the other data structures in this library, dm_bitset objects are
* immutable between transactions. Update functions will return you the
* root for a _new_ array. If you've incremented the old root, via
* dm_tm_inc(), before calling the update function you may continue to use
* it in parallel with the new root.
*
* Even read operations may trigger the cache to be flushed and as such
* return a root for a new, updated bitset.
*
* c) resize a bitset with dm_bitset_resize().
*
* d) Set a bit with dm_bitset_set_bit().
*
* e) Clear a bit with dm_bitset_clear_bit().
*
* f) Test a bit with dm_bitset_test_bit().
*
* g) Flush all updates from the cache with dm_bitset_flush().
*
* h) Destroy the bitset with dm_bitset_del(). This tells the transaction
* manager that you're no longer using this data structure so it can
* recycle it's blocks. (dm_bitset_dec() would be a better name for it,
* but del is in keeping with dm_btree_del()).
*/
/*
* Opaque object. Unlike dm_array_info, you should have one of these per
* bitset. Initialise with dm_disk_bitset_init().
*/
struct dm_disk_bitset {
struct dm_array_info array_info;
uint32_t current_index;
uint64_t current_bits;
bool current_index_set:1;
bool dirty:1;
};
/*
* Sets up a dm_disk_bitset structure. You don't need to do anything with
* this structure when you finish using it.
*
* tm - the transaction manager that should supervise this structure
* info - the structure being initialised
*/
void dm_disk_bitset_init(struct dm_transaction_manager *tm,
struct dm_disk_bitset *info);
/*
* Create an empty, zero length bitset.
*
* info - describes the bitset
* new_root - on success, points to the new root block
*/
int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
/*
* Resize the bitset.
*
* info - describes the bitset
* old_root - the root block of the array on disk
* old_nr_entries - the number of bits in the old bitset
* new_nr_entries - the number of bits you want in the new bitset
* default_value - the value for any new bits
* new_root - on success, points to the new root block
*/
int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t old_root,
uint32_t old_nr_entries, uint32_t new_nr_entries,
bool default_value, dm_block_t *new_root);
/*
* Frees the bitset.
*/
int dm_bitset_del(struct dm_disk_bitset *info, dm_block_t root);
/*
* Set a bit.
*
* info - describes the bitset
* root - the root block of the bitset
* index - the bit index
* new_root - on success, points to the new root block
*
* -ENODATA will be returned if the index is out of bounds.
*/
int dm_bitset_set_bit(struct dm_disk_bitset *info, dm_block_t root,
uint32_t index, dm_block_t *new_root);
/*
* Clears a bit.
*
* info - describes the bitset
* root - the root block of the bitset
* index - the bit index
* new_root - on success, points to the new root block
*
* -ENODATA will be returned if the index is out of bounds.
*/
int dm_bitset_clear_bit(struct dm_disk_bitset *info, dm_block_t root,
uint32_t index, dm_block_t *new_root);
/*
* Tests a bit.
*
* info - describes the bitset
* root - the root block of the bitset
* index - the bit index
* new_root - on success, points to the new root block (cached values may have been written)
* result - the bit value you're after
*
* -ENODATA will be returned if the index is out of bounds.
*/
int dm_bitset_test_bit(struct dm_disk_bitset *info, dm_block_t root,
uint32_t index, dm_block_t *new_root, bool *result);
/*
* Flush any cached changes to disk.
*
* info - describes the bitset
* root - the root block of the bitset
* new_root - on success, points to the new root block
*/
int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
dm_block_t *new_root);
/*----------------------------------------------------------------*/
#endif /* _LINUX_DM_BITSET_H */
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