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428e469864
This change offers a big performance boost for dm-era. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
167 lines
5.2 KiB
C
167 lines
5.2 KiB
C
/*
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* Copyright (C) 2012 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_BITSET_H
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#define _LINUX_DM_BITSET_H
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#include "dm-array.h"
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/*----------------------------------------------------------------*/
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/*
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* This bitset type is a thin wrapper round a dm_array of 64bit words. It
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* uses a tiny, one word cache to reduce the number of array lookups and so
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* increase performance.
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*
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* Like the dm-array that it's based on, the caller needs to keep track of
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* the size of the bitset separately. The underlying dm-array implicitly
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* knows how many words it's storing and will return -ENODATA if you try
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* and access an out of bounds word. However, an out of bounds bit in the
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* final word will _not_ be detected, you have been warned.
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*
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* Bits are indexed from zero.
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* Typical use:
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*
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* a) Initialise a dm_disk_bitset structure with dm_disk_bitset_init().
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* This describes the bitset and includes the cache. It's not called it
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* dm_bitset_info in line with other data structures because it does
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* include instance data.
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*
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* b) Get yourself a root. The root is the index of a block of data on the
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* disk that holds a particular instance of an bitset. You may have a
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* pre existing root in your metadata that you wish to use, or you may
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* want to create a brand new, empty bitset with dm_bitset_empty().
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*
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* Like the other data structures in this library, dm_bitset objects are
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* immutable between transactions. Update functions will return you the
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* root for a _new_ array. If you've incremented the old root, via
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* dm_tm_inc(), before calling the update function you may continue to use
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* it in parallel with the new root.
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*
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* Even read operations may trigger the cache to be flushed and as such
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* return a root for a new, updated bitset.
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*
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* c) resize a bitset with dm_bitset_resize().
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*
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* d) Set a bit with dm_bitset_set_bit().
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*
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* e) Clear a bit with dm_bitset_clear_bit().
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*
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* f) Test a bit with dm_bitset_test_bit().
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*
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* g) Flush all updates from the cache with dm_bitset_flush().
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*
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* h) Destroy the bitset with dm_bitset_del(). This tells the transaction
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* manager that you're no longer using this data structure so it can
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* recycle it's blocks. (dm_bitset_dec() would be a better name for it,
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* but del is in keeping with dm_btree_del()).
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*/
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/*
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* Opaque object. Unlike dm_array_info, you should have one of these per
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* bitset. Initialise with dm_disk_bitset_init().
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*/
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struct dm_disk_bitset {
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struct dm_array_info array_info;
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uint32_t current_index;
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uint64_t current_bits;
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bool current_index_set:1;
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bool dirty:1;
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};
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/*
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* Sets up a dm_disk_bitset structure. You don't need to do anything with
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* this structure when you finish using it.
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*
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* tm - the transaction manager that should supervise this structure
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* info - the structure being initialised
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*/
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void dm_disk_bitset_init(struct dm_transaction_manager *tm,
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struct dm_disk_bitset *info);
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/*
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* Create an empty, zero length bitset.
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*
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* info - describes the bitset
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* new_root - on success, points to the new root block
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*/
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int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
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/*
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* Resize the bitset.
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*
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* info - describes the bitset
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* old_root - the root block of the array on disk
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* old_nr_entries - the number of bits in the old bitset
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* new_nr_entries - the number of bits you want in the new bitset
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* default_value - the value for any new bits
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* new_root - on success, points to the new root block
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*/
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int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t old_root,
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uint32_t old_nr_entries, uint32_t new_nr_entries,
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bool default_value, dm_block_t *new_root);
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/*
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* Frees the bitset.
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*/
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int dm_bitset_del(struct dm_disk_bitset *info, dm_block_t root);
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/*
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* Set a bit.
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*
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* info - describes the bitset
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* root - the root block of the bitset
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* index - the bit index
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* new_root - on success, points to the new root block
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*
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* -ENODATA will be returned if the index is out of bounds.
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*/
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int dm_bitset_set_bit(struct dm_disk_bitset *info, dm_block_t root,
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uint32_t index, dm_block_t *new_root);
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/*
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* Clears a bit.
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*
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* info - describes the bitset
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* root - the root block of the bitset
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* index - the bit index
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* new_root - on success, points to the new root block
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*
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* -ENODATA will be returned if the index is out of bounds.
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*/
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int dm_bitset_clear_bit(struct dm_disk_bitset *info, dm_block_t root,
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uint32_t index, dm_block_t *new_root);
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/*
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* Tests a bit.
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*
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* info - describes the bitset
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* root - the root block of the bitset
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* index - the bit index
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* new_root - on success, points to the new root block (cached values may have been written)
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* result - the bit value you're after
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*
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* -ENODATA will be returned if the index is out of bounds.
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*/
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int dm_bitset_test_bit(struct dm_disk_bitset *info, dm_block_t root,
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uint32_t index, dm_block_t *new_root, bool *result);
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/*
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* Flush any cached changes to disk.
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*
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* info - describes the bitset
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* root - the root block of the bitset
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* new_root - on success, points to the new root block
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*/
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int dm_bitset_flush(struct dm_disk_bitset *info, dm_block_t root,
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dm_block_t *new_root);
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/*----------------------------------------------------------------*/
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#endif /* _LINUX_DM_BITSET_H */
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