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Fix bloom filter bugs

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The bloom filter had two bad bugs.

First the calculation was adding the bit width of newly hashed data to
the hash value instead of the record of the hashed bits available.

And the block offset calculation for each bit wasn't truncated to the
number of bloom blocks.  While fixing this we can clean up the code and
make it faster by recording the bits in terms of their block and bit
offset instead of their large bit value.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2016-03-23 22:23:21 -04:00
parent ddf5ef1017
commit e0e6179156
2 changed files with 12 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
utils/src/bloom.c
View File

@@ -31,6 +31,7 @@ void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,
struct scoutfs_key *key, __le32 *salts)
{
unsigned h_bits = 0;
unsigned int b;
unsigned s = 0;
u64 h = 0;
int i;
@@ -38,12 +39,16 @@ void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,
for (i = 0; i < SCOUTFS_BLOOM_BITS; i++) {
if (h_bits < SCOUTFS_BLOOM_BIT_WIDTH) {
h = (h << 32) | bloom_hash(key, salts[s++]);
h += 32;
h_bits += 32;
}
bits->nr[i] = h & SCOUTFS_BLOOM_BIT_MASK;
b = h & SCOUTFS_BLOOM_BIT_MASK;
h >>= SCOUTFS_BLOOM_BIT_WIDTH;
h_bits -= SCOUTFS_BLOOM_BIT_WIDTH;
bits->block[i] = (b / SCOUTFS_BLOOM_BITS_PER_BLOCK) %
SCOUTFS_BLOOM_BLOCKS;
bits->bit_off[i] = b % SCOUTFS_BLOOM_BITS_PER_BLOCK;
}
}
@@ -51,16 +56,15 @@ void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,
* This interface is different than in the kernel because we don't
* have a block IO interface here yet. The caller gives us each
* bloom block and we set each bit that falls in the block.
*/
*/
void scoutfs_set_bloom_bits(struct scoutfs_bloom_block *blm, unsigned int nr,
struct scoutfs_bloom_bits *bits)
{
int i;
for (i = 0; i < SCOUTFS_BLOOM_BITS; i++) {
if (nr == (bits->nr[i] / SCOUTFS_BLOOM_BITS_PER_BLOCK)) {
set_bit_le(bits->nr[i] % SCOUTFS_BLOOM_BITS_PER_BLOCK,
blm->bits);
if (nr == bits->block[i]) {
set_bit_le(bits->bit_off[i], blm->bits);
}
}
}

3
utils/src/bloom.h
View File

@@ -2,7 +2,8 @@
#define _BLOOM_H_
struct scoutfs_bloom_bits {
u32 nr[SCOUTFS_BLOOM_BITS];
u16 bit_off[SCOUTFS_BLOOM_BITS];
u8 block[SCOUTFS_BLOOM_BITS];
};
void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,