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dm bitset: add dm_bitset_new()

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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>
This commit is contained in:
Joe Thornber 2016-09-22 10:44:41 -04:00 committed by Mike Snitzer
parent 48551054fc
commit 2151249eaa
2 changed files with 58 additions and 0 deletions
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42
drivers/md/persistent-data/dm-bitset.c
View file

@ -39,6 +39,48 @@ int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *root)
}
EXPORT_SYMBOL_GPL(dm_bitset_empty);
struct packer_context {
bit_value_fn fn;
unsigned nr_bits;
void *context;
};
static int pack_bits(uint32_t index, void *value, void *context)
{
int r;
struct packer_context *p = context;
unsigned bit, nr = min(64u, p->nr_bits - (index * 64));
uint64_t word = 0;
bool bv;
for (bit = 0; bit < nr; bit++) {
r = p->fn(index * 64 + bit, &bv, p->context);
if (r)
return r;
if (bv)
set_bit(bit, (unsigned long *) &word);
else
clear_bit(bit, (unsigned long *) &word);
}
*((__le64 *) value) = cpu_to_le64(word);
return 0;
}
int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
uint32_t size, bit_value_fn fn, void *context)
{
struct packer_context p;
p.fn = fn;
p.nr_bits = size;
p.context = context;
return dm_array_new(&info->array_info, root, dm_div_up(size, 64), pack_bits, &p);
}
EXPORT_SYMBOL_GPL(dm_bitset_new);
int dm_bitset_resize(struct dm_disk_bitset *info, dm_block_t root,
uint32_t old_nr_entries, uint32_t new_nr_entries,
bool default_value, dm_block_t *new_root)

16
drivers/md/persistent-data/dm-bitset.h
View file

@ -92,6 +92,22 @@ void dm_disk_bitset_init(struct dm_transaction_manager *tm,
*/
int dm_bitset_empty(struct dm_disk_bitset *info, dm_block_t *new_root);
/*
* Creates a new bitset populated with values provided by a callback
* function. This is more efficient than creating an empty bitset,
* resizing, and then setting values since that process incurs a lot of
* copying.
*
* info - describes the array
* root - the root block of the array on disk
* size - the number of entries in the array
* fn - the callback
* context - passed to the callback
*/
typedef int (*bit_value_fn)(uint32_t index, bool *value, void *context);
int dm_bitset_new(struct dm_disk_bitset *info, dm_block_t *root,
uint32_t size, bit_value_fn fn, void *context);
/*
* Resize the bitset.
*