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/*
* Copyright (C) 2011 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#ifndef _LINUX_DM_BLOCK_MANAGER_H
#define _LINUX_DM_BLOCK_MANAGER_H
#include <linux/types.h>
#include <linux/blkdev.h>
/*----------------------------------------------------------------*/
/*
* Block number.
*/
typedef uint64_t dm_block_t;
struct dm_block;
dm_block_t dm_block_location(struct dm_block *b);
void *dm_block_data(struct dm_block *b);
/*----------------------------------------------------------------*/
/*
* @name should be a unique identifier for the block manager, no longer
* than 32 chars.
*
* @max_held_per_thread should be the maximum number of locks, read or
* write, that an individual thread holds at any one time.
*/
struct dm_block_manager;
struct dm_block_manager *dm_block_manager_create(
struct block_device *bdev, unsigned block_size,
unsigned cache_size, unsigned max_held_per_thread);
void dm_block_manager_destroy(struct dm_block_manager *bm);
unsigned dm_bm_block_size(struct dm_block_manager *bm);
dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
/*----------------------------------------------------------------*/
/*
* The validator allows the caller to verify newly-read data and modify
* the data just before writing, e.g. to calculate checksums. It's
* important to be consistent with your use of validators. The only time
* you can change validators is if you call dm_bm_write_lock_zero.
*/
struct dm_block_validator {
const char *name;
void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
/*
* Return 0 if the checksum is valid or < 0 on error.
*/
int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
};
/*----------------------------------------------------------------*/
/*
* You can have multiple concurrent readers or a single writer holding a
* block lock.
*/
/*
* dm_bm_lock() locks a block and returns through @result a pointer to
* memory that holds a copy of that block. If you have write-locked the
* block then any changes you make to memory pointed to by @result will be
* written back to the disk sometime after dm_bm_unlock is called.
*/
int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **result);
int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **result);
/*
* The *_try_lock variants return -EWOULDBLOCK if the block isn't
* available immediately.
*/
int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **result);
/*
* Use dm_bm_write_lock_zero() when you know you're going to
* overwrite the block completely. It saves a disk read.
*/
int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **result);
int dm_bm_unlock(struct dm_block *b);
/*
* An optimisation; we often want to copy a block's contents to a new
* block. eg, as part of the shadowing operation. It's far better for
* bufio to do this move behind the scenes than hold 2 locks and memcpy the
* data.
*/
int dm_bm_unlock_move(struct dm_block *b, dm_block_t n);
/*
* It's a common idiom to have a superblock that should be committed last.
*
* @superblock should be write-locked on entry. It will be unlocked during
* this function. All dirty blocks are guaranteed to be written and flushed
* before the superblock.
*
* This method always blocks.
*/
int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
struct dm_block *superblock);
u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
/*----------------------------------------------------------------*/
#endif /* _LINUX_DM_BLOCK_MANAGER_H */
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