mirror of
https://github.com/torvalds/linux.git
synced 2024-12-09 04:31:39 +00:00
6513c29f44
Add a transactional array. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
167 lines
5.6 KiB
C
167 lines
5.6 KiB
C
/*
|
|
* Copyright (C) 2012 Red Hat, Inc.
|
|
*
|
|
* This file is released under the GPL.
|
|
*/
|
|
#ifndef _LINUX_DM_ARRAY_H
|
|
#define _LINUX_DM_ARRAY_H
|
|
|
|
#include "dm-btree.h"
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
/*
|
|
* The dm-array is a persistent version of an array. It packs the data
|
|
* more efficiently than a btree which will result in less disk space use,
|
|
* and a performance boost. The element get and set operations are still
|
|
* O(ln(n)), but with a much smaller constant.
|
|
*
|
|
* The value type structure is reused from the btree type to support proper
|
|
* reference counting of values.
|
|
*
|
|
* The arrays implicitly know their length, and bounds are checked for
|
|
* lookups and updated. It doesn't store this in an accessible place
|
|
* because it would waste a whole metadata block. Make sure you store the
|
|
* size along with the array root in your encompassing data.
|
|
*
|
|
* Array entries are indexed via an unsigned integer starting from zero.
|
|
* Arrays are not sparse; if you resize an array to have 'n' entries then
|
|
* 'n - 1' will be the last valid index.
|
|
*
|
|
* Typical use:
|
|
*
|
|
* a) initialise a dm_array_info structure. This describes the array
|
|
* values and ties it into a specific transaction manager. It holds no
|
|
* instance data; the same info can be used for many similar arrays if
|
|
* you wish.
|
|
*
|
|
* 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 array. 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 array with dm_array_empty().
|
|
*
|
|
* Like the other data structures in this library, dm_array 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.
|
|
*
|
|
* c) resize an array with dm_array_resize().
|
|
*
|
|
* d) Get a value from the array with dm_array_get_value().
|
|
*
|
|
* e) Set a value in the array with dm_array_set_value().
|
|
*
|
|
* f) Walk an array of values in index order with dm_array_walk(). More
|
|
* efficient than making many calls to dm_array_get_value().
|
|
*
|
|
* g) Destroy the array with dm_array_del(). This tells the transaction
|
|
* manager that you're no longer using this data structure so it can
|
|
* recycle it's blocks. (dm_array_dec() would be a better name for it,
|
|
* but del is in keeping with dm_btree_del()).
|
|
*/
|
|
|
|
/*
|
|
* Describes an array. Don't initialise this structure yourself, use the
|
|
* init function below.
|
|
*/
|
|
struct dm_array_info {
|
|
struct dm_transaction_manager *tm;
|
|
struct dm_btree_value_type value_type;
|
|
struct dm_btree_info btree_info;
|
|
};
|
|
|
|
/*
|
|
* Sets up a dm_array_info structure. You don't need to do anything with
|
|
* this structure when you finish using it.
|
|
*
|
|
* info - the structure being filled in.
|
|
* tm - the transaction manager that should supervise this structure.
|
|
* vt - describes the leaf values.
|
|
*/
|
|
void dm_array_info_init(struct dm_array_info *info,
|
|
struct dm_transaction_manager *tm,
|
|
struct dm_btree_value_type *vt);
|
|
|
|
/*
|
|
* Create an empty, zero length array.
|
|
*
|
|
* info - describes the array
|
|
* root - on success this will be filled out with the root block
|
|
*/
|
|
int dm_array_empty(struct dm_array_info *info, dm_block_t *root);
|
|
|
|
/*
|
|
* Resizes the array.
|
|
*
|
|
* info - describes the array
|
|
* root - the root block of the array on disk
|
|
* old_size - the caller is responsible for remembering the size of
|
|
* the array
|
|
* new_size - can be bigger or smaller than old_size
|
|
* value - if we're growing the array the new entries will have this value
|
|
* new_root - on success, points to the new root block
|
|
*
|
|
* If growing the inc function for 'value' will be called the appropriate
|
|
* number of times. So if the caller is holding a reference they may want
|
|
* to drop it.
|
|
*/
|
|
int dm_array_resize(struct dm_array_info *info, dm_block_t root,
|
|
uint32_t old_size, uint32_t new_size,
|
|
const void *value, dm_block_t *new_root)
|
|
__dm_written_to_disk(value);
|
|
|
|
/*
|
|
* Frees a whole array. The value_type's decrement operation will be called
|
|
* for all values in the array
|
|
*/
|
|
int dm_array_del(struct dm_array_info *info, dm_block_t root);
|
|
|
|
/*
|
|
* Lookup a value in the array
|
|
*
|
|
* info - describes the array
|
|
* root - root block of the array
|
|
* index - array index
|
|
* value - the value to be read. Will be in on-disk format of course.
|
|
*
|
|
* -ENODATA will be returned if the index is out of bounds.
|
|
*/
|
|
int dm_array_get_value(struct dm_array_info *info, dm_block_t root,
|
|
uint32_t index, void *value);
|
|
|
|
/*
|
|
* Set an entry in the array.
|
|
*
|
|
* info - describes the array
|
|
* root - root block of the array
|
|
* index - array index
|
|
* value - value to be written to disk. Make sure you confirm the value is
|
|
* in on-disk format with__dm_bless_for_disk() before calling.
|
|
* new_root - the new root block
|
|
*
|
|
* The old value being overwritten will be decremented, the new value
|
|
* incremented.
|
|
*
|
|
* -ENODATA will be returned if the index is out of bounds.
|
|
*/
|
|
int dm_array_set_value(struct dm_array_info *info, dm_block_t root,
|
|
uint32_t index, const void *value, dm_block_t *new_root)
|
|
__dm_written_to_disk(value);
|
|
|
|
/*
|
|
* Walk through all the entries in an array.
|
|
*
|
|
* info - describes the array
|
|
* root - root block of the array
|
|
* fn - called back for every element
|
|
* context - passed to the callback
|
|
*/
|
|
int dm_array_walk(struct dm_array_info *info, dm_block_t root,
|
|
int (*fn)(void *context, uint64_t key, void *leaf),
|
|
void *context);
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
#endif /* _LINUX_DM_ARRAY_H */
|