1/*
  2 * Copyright (C) 2011 Red Hat, Inc.
  3 *
  4 * This file is released under the GPL.
  5 */
  6
  7#ifndef _LINUX_DM_TRANSACTION_MANAGER_H
  8#define _LINUX_DM_TRANSACTION_MANAGER_H
  9
 10#include "dm-block-manager.h"
 11
 12struct dm_transaction_manager;
 13struct dm_space_map;
 14
 15/*----------------------------------------------------------------*/
 16
 17/*
 18 * This manages the scope of a transaction.  It also enforces immutability
 19 * of the on-disk data structures by limiting access to writeable blocks.
 20 *
 21 * Clients should not fiddle with the block manager directly.
 22 */
 23
 24void dm_tm_destroy(struct dm_transaction_manager *tm);
 25
 26/*
 27 * The non-blocking version of a transaction manager is intended for use in
 28 * fast path code that needs to do lookups e.g. a dm mapping function.
 29 * You create the non-blocking variant from a normal tm.  The interface is
 30 * the same, except that most functions will just return -EWOULDBLOCK.
 31 * Methods that return void yet may block should not be called on a clone
 32 * viz. dm_tm_inc, dm_tm_dec.  Call dm_tm_destroy() as you would with a normal
 33 * tm when you've finished with it.  You may not destroy the original prior
 34 * to clones.
 35 */
 36struct dm_transaction_manager *dm_tm_create_non_blocking_clone(struct dm_transaction_manager *real);
 37
 38/*
 39 * We use a 2-phase commit here.
 40 *
 41 * i) Make all changes for the transaction *except* for the superblock.
 42 * Then call dm_tm_pre_commit() to flush them to disk.
 43 *
 44 * ii) Lock your superblock.  Update.  Then call dm_tm_commit() which will
 45 * unlock the superblock and flush it.  No other blocks should be updated
 46 * during this period.  Care should be taken to never unlock a partially
 47 * updated superblock; perform any operations that could fail *before* you
 48 * take the superblock lock.
 49 */
 50int dm_tm_pre_commit(struct dm_transaction_manager *tm);
 51int dm_tm_commit(struct dm_transaction_manager *tm, struct dm_block *superblock);
 52
 53/*
 54 * These methods are the only way to get hold of a writeable block.
 55 */
 56
 57/*
 58 * dm_tm_new_block() is pretty self-explanatory.  Make sure you do actually
 59 * write to the whole of @data before you unlock, otherwise you could get
 60 * a data leak.  (The other option is for tm_new_block() to zero new blocks
 61 * before handing them out, which will be redundant in most, if not all,
 62 * cases).
 63 * Zeroes the new block and returns with write lock held.
 64 */
 65int dm_tm_new_block(struct dm_transaction_manager *tm,
 66		    struct dm_block_validator *v,
 67		    struct dm_block **result);
 68
 69/*
 70 * dm_tm_shadow_block() allocates a new block and copies the data from @orig
 71 * to it.  It then decrements the reference count on original block.  Use
 72 * this to update the contents of a block in a data structure, don't
 73 * confuse this with a clone - you shouldn't access the orig block after
 74 * this operation.  Because the tm knows the scope of the transaction it
 75 * can optimise requests for a shadow of a shadow to a no-op.  Don't forget
 76 * to unlock when you've finished with the shadow.
 77 *
 78 * The @inc_children flag is used to tell the caller whether it needs to
 79 * adjust reference counts for children.  (Data in the block may refer to
 80 * other blocks.)
 81 *
 82 * Shadowing implicitly drops a reference on @orig so you must not have
 83 * it locked when you call this.
 84 */
 85int dm_tm_shadow_block(struct dm_transaction_manager *tm, dm_block_t orig,
 86		       struct dm_block_validator *v,
 87		       struct dm_block **result, int *inc_children);
 88
 89/*
 90 * Read access.  You can lock any block you want.  If there's a write lock
 91 * on it outstanding then it'll block.
 92 */
 93int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
 94		    struct dm_block_validator *v,
 95		    struct dm_block **result);
 96
 97void dm_tm_unlock(struct dm_transaction_manager *tm, struct dm_block *b);
 98
 99/*
100 * Functions for altering the reference count of a block directly.
101 */
102void dm_tm_inc(struct dm_transaction_manager *tm, dm_block_t b);
103
104void dm_tm_dec(struct dm_transaction_manager *tm, dm_block_t b);
105
106int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
107	      uint32_t *result);
108
109struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm);
110
111/*
112 * If you're using a non-blocking clone the tm will build up a list of
113 * requested blocks that weren't in core.  This call will request those
114 * blocks to be prefetched.
115 */
116void dm_tm_issue_prefetches(struct dm_transaction_manager *tm);
117
118/*
119 * A little utility that ties the knot by producing a transaction manager
120 * that has a space map managed by the transaction manager...
121 *
122 * Returns a tm that has an open transaction to write the new disk sm.
123 * Caller should store the new sm root and commit.
124 *
125 * The superblock location is passed so the metadata space map knows it
126 * shouldn't be used.
127 */
128int dm_tm_create_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
129			 struct dm_transaction_manager **tm,
130			 struct dm_space_map **sm);
131
132int dm_tm_open_with_sm(struct dm_block_manager *bm, dm_block_t sb_location,
133		       void *sm_root, size_t root_len,
134		       struct dm_transaction_manager **tm,
135		       struct dm_space_map **sm);
136
137#endif	/* _LINUX_DM_TRANSACTION_MANAGER_H */