3241b1d3e0
The persistent-data library offers a re-usable framework for the storage and management of on-disk metadata in device-mapper targets. It's used by the thin-provisioning target in the next patch and in an upcoming hierarchical storage target. For further information, please read Documentation/device-mapper/persistent-data.txt Signed-off-by: Joe Thornber <thornber@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
124 lines
3.8 KiB
C
124 lines
3.8 KiB
C
/*
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* Copyright (C) 2011 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*/
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#ifndef _LINUX_DM_BLOCK_MANAGER_H
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#define _LINUX_DM_BLOCK_MANAGER_H
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#include <linux/types.h>
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#include <linux/blkdev.h>
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/*----------------------------------------------------------------*/
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/*
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* Block number.
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*/
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typedef uint64_t dm_block_t;
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struct dm_block;
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dm_block_t dm_block_location(struct dm_block *b);
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void *dm_block_data(struct dm_block *b);
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/*----------------------------------------------------------------*/
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/*
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* @name should be a unique identifier for the block manager, no longer
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* than 32 chars.
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*
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* @max_held_per_thread should be the maximum number of locks, read or
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* write, that an individual thread holds at any one time.
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*/
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struct dm_block_manager;
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struct dm_block_manager *dm_block_manager_create(
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struct block_device *bdev, unsigned block_size,
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unsigned cache_size, unsigned max_held_per_thread);
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void dm_block_manager_destroy(struct dm_block_manager *bm);
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unsigned dm_bm_block_size(struct dm_block_manager *bm);
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dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
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/*----------------------------------------------------------------*/
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/*
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* The validator allows the caller to verify newly-read data and modify
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* the data just before writing, e.g. to calculate checksums. It's
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* important to be consistent with your use of validators. The only time
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* you can change validators is if you call dm_bm_write_lock_zero.
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*/
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struct dm_block_validator {
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const char *name;
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void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
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/*
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* Return 0 if the checksum is valid or < 0 on error.
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*/
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int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
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};
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/*----------------------------------------------------------------*/
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/*
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* You can have multiple concurrent readers or a single writer holding a
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* block lock.
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*/
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/*
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* dm_bm_lock() locks a block and returns through @result a pointer to
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* memory that holds a copy of that block. If you have write-locked the
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* block then any changes you make to memory pointed to by @result will be
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* written back to the disk sometime after dm_bm_unlock is called.
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*/
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int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
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struct dm_block_validator *v,
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struct dm_block **result);
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int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
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struct dm_block_validator *v,
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struct dm_block **result);
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/*
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* The *_try_lock variants return -EWOULDBLOCK if the block isn't
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* available immediately.
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*/
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int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
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struct dm_block_validator *v,
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struct dm_block **result);
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/*
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* Use dm_bm_write_lock_zero() when you know you're going to
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* overwrite the block completely. It saves a disk read.
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*/
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int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
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struct dm_block_validator *v,
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struct dm_block **result);
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int dm_bm_unlock(struct dm_block *b);
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/*
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* An optimisation; we often want to copy a block's contents to a new
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* block. eg, as part of the shadowing operation. It's far better for
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* bufio to do this move behind the scenes than hold 2 locks and memcpy the
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* data.
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*/
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int dm_bm_unlock_move(struct dm_block *b, dm_block_t n);
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/*
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* It's a common idiom to have a superblock that should be committed last.
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*
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* @superblock should be write-locked on entry. It will be unlocked during
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* this function. All dirty blocks are guaranteed to be written and flushed
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* before the superblock.
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*
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* This method always blocks.
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*/
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int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
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struct dm_block *superblock);
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u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
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/*----------------------------------------------------------------*/
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#endif /* _LINUX_DM_BLOCK_MANAGER_H */
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