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Diffstat (limited to 'drivers/md/persistent-data/dm-transaction-manager.h')
| -rw-r--r-- | drivers/md/persistent-data/dm-transaction-manager.h | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/drivers/md/persistent-data/dm-transaction-manager.h b/drivers/md/persistent-data/dm-transaction-manager.h new file mode 100644 index 000000000..f3a18be68 --- /dev/null +++ b/drivers/md/persistent-data/dm-transaction-manager.h @@ -0,0 +1,137 @@ +/* + * 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) Make all changes for the transaction *except* for the superblock. + * Then call dm_tm_pre_commit() to flush them to disk. + * + * ii) Lock your superblock. Update. Then call dm_tm_commit() which will + * unlock the superblock and flush it. No other blocks should be updated + * during this period. Care should be taken to never unlock a partially + * updated superblock; perform any operations that could fail *before* you + * take the superblock lock. + */ +int dm_tm_pre_commit(struct dm_transaction_manager *tm); +int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *superblock); + +/* + * 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); + +void 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); + +/* + * If you're using a non-blocking clone the tm will build up a list of + * requested blocks that weren't in core. This call will request those + * blocks to be prefetched. + */ +void dm_tm_issue_prefetches(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. + * + * The superblock location is passed so the metadata space map knows it + * shouldn't be used. + */ +int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location, + struct dm_transaction_manager **tm, + struct dm_space_map **sm); + +int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location, + void *sm_root, size_t root_len, + struct dm_transaction_manager **tm, + struct dm_space_map **sm); + +#endif /* _LINUX_DM_TRANSACTION_MANAGER_H */ |