dm-transaction-manager.h
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/*
* Copyright (C) 2011 Red Hat, Inc.
*
* This file is released under the GPL.
*/
#ifndef _LINUX_DM_TRANSACTION_MANAGER_H
#define _LINUX_DM_TRANSACTION_MANAGER_H
#include "dm-block-manager.h"
struct dm_transaction_manager;
struct dm_space_map;
/*----------------------------------------------------------------*/
/*
* This manages the scope of a transaction. It also enforces immutability
* of the on-disk data structures by limiting access to writeable blocks.
*
* Clients should not fiddle with the block manager directly.
*/
void dm_tm_destroy(struct dm_transaction_manager *tm);
/*
* The non-blocking version of a transaction manager is intended for use in
* fast path code that needs to do lookups e.g. a dm mapping function.
* You create the non-blocking variant from a normal tm. The interface is
* the same, except that most functions will just return -EWOULDBLOCK.
* Methods that return void yet may block should not be called on a clone
* viz. dm_tm_inc, dm_tm_dec. Call dm_tm_destroy() as you would with a normal
* tm when you've finished with it. You may not destroy the original prior
* to clones.
*/
struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real);
/*
* We use a 2-phase commit here.
*
* i) In the first phase the block manager is told to start flushing, and
* the changes to the space map are written to disk. You should interrogate
* your particular space map to get detail of its root node etc. to be
* included in your superblock.
*
* ii) @root will be committed last. You shouldn't use more than the
* first 512 bytes of @root if you wish the transaction to survive a power
* failure. You *must* have a write lock held on @root for both stage (i)
* and (ii). The commit will drop the write lock.
*/
int dm_tm_pre_commit(struct dm_transaction_manager *tm);
int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *root);
/*
* These methods are the only way to get hold of a writeable block.
*/
/*
* dm_tm_new_block() is pretty self-explanatory. Make sure you do actually
* write to the whole of @data before you unlock, otherwise you could get
* a data leak. (The other option is for tm_new_block() to zero new blocks
* before handing them out, which will be redundant in most, if not all,
* cases).
* Zeroes the new block and returns with write lock held.
*/
int dm_tm_new_block(struct dm_transaction_manager *tm,
struct dm_block_validator *v,
struct dm_block **result);
/*
* dm_tm_shadow_block() allocates a new block and copies the data from @orig
* to it. It then decrements the reference count on original block. Use
* this to update the contents of a block in a data structure, don't
* confuse this with a clone - you shouldn't access the orig block after
* this operation. Because the tm knows the scope of the transaction it
* can optimise requests for a shadow of a shadow to a no-op. Don't forget
* to unlock when you've finished with the shadow.
*
* The @inc_children flag is used to tell the caller whether it needs to
* adjust reference counts for children. (Data in the block may refer to
* other blocks.)
*
* Shadowing implicitly drops a reference on @orig so you must not have
* it locked when you call this.
*/
int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
struct dm_block_validator *v,
struct dm_block **result, int *inc_children);
/*
* Read access. You can lock any block you want. If there's a write lock
* on it outstanding then it'll block.
*/
int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **result);
int dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b);
/*
* Functions for altering the reference count of a block directly.
*/
void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b);
void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b);
int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
uint32_t *result);
struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm);
/*
* A little utility that ties the knot by producing a transaction manager
* that has a space map managed by the transaction manager...
*
* Returns a tm that has an open transaction to write the new disk sm.
* Caller should store the new sm root and commit.
*/
int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
struct dm_block_validator *sb_validator,
struct dm_transaction_manager **tm,
struct dm_space_map **sm, struct dm_block **sblock);
int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
struct dm_block_validator *sb_validator,
size_t root_offset, size_t root_max_len,
struct dm_transaction_manager **tm,
struct dm_space_map **sm, struct dm_block **sblock);
#endif /* _LINUX_DM_TRANSACTION_MANAGER_H */