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dm bitset: add dm_bitset_new()
A more efficient way of creating a populated bitset. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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2 changed files with 58 additions and 0 deletions
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@ -39,6 +39,48 @@ int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *root)
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}
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EXPORT_SYMBOL_GPL(dm_bitset_empty);
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struct packer_context {
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bit_value_fn fn;
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unsigned nr_bits;
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void *context;
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};
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static int pack_bits(uint32_t index, void *value, void *context)
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{
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int r;
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struct packer_context *p = context;
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unsigned bit, nr = min(64u, p->nr_bits - (index * 64));
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uint64_t word = 0;
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bool bv;
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for (bit = 0; bit < nr; bit++) {
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r = p->fn(index * 64 + bit, &bv, p->context);
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if (r)
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return r;
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if (bv)
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set_bit(bit, (unsigned long *) &word);
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else
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clear_bit(bit, (unsigned long *) &word);
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}
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*((__le64 *) value) = cpu_to_le64(word);
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return 0;
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}
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int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
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uint32_t size, bit_value_fn fn, void *context)
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{
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struct packer_context p;
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p.fn = fn;
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p.nr_bits = size;
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p.context = context;
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return dm_array_new(&info->array_info, root, dm_div_up(size, 64), pack_bits, &p);
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}
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EXPORT_SYMBOL_GPL(dm_bitset_new);
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int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t 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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@ -92,6 +92,22 @@ void dm_disk_bitset_init(struct dm_transaction_manager *tm,
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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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* Creates a new bitset populated with values provided by a callback
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* function. This is more efficient than creating an empty bitset,
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* resizing, and then setting values since that process incurs a lot of
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* copying.
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*
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* info - describes the array
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* root - the root block of the array on disk
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* size - the number of entries in the array
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* fn - the callback
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* context - passed to the callback
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*/
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typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
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int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
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uint32_t size, bit_value_fn fn, void *context);
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/*
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* Resize the bitset.
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*
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