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Add minimal bloom filter helpers

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mkfs just needs to initialize bloom filter blocks with the bits for the
single root inode key.  We can get away with these skeletal functions
for now.

Signed-off-by: Zach Brown <zab@versity.com>
This commit is contained in:
Zach Brown
2016-03-23 14:01:16 -07:00
parent 8471134328
commit d0429e1c88
2 changed files with 79 additions and 0 deletions
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66
utils/src/bloom.c Normal file
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/*
* Copyright (C) 2016 Versity Software, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include "sparse.h"
#include "util.h"
#include "format.h"
#include "bloom.h"
#include "crc.h"
#include "bitops.h"
/* XXX garbage hack until we have siphash */
static u32 bloom_hash(struct scoutfs_key *key, __le32 salt)
{
return crc32c(le32_to_cpu(salt), key, sizeof(struct scoutfs_key));
}
/*
* Find the bits in the bloom filter for the given key. The caller calculates
* these once and uses them to test all the blocks.
*/
void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,
struct scoutfs_key *key, __le32 *salts)
{
unsigned h_bits = 0;
unsigned s = 0;
u64 h = 0;
int i;
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;
}
bits->nr[i] = h & SCOUTFS_BLOOM_BIT_MASK;
h >>= SCOUTFS_BLOOM_BIT_WIDTH;
h_bits -= SCOUTFS_BLOOM_BIT_WIDTH;
}
}
/*
* 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);
}
}
}

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utils/src/bloom.h Normal file
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#ifndef _BLOOM_H_
#define _BLOOM_H_
struct scoutfs_bloom_bits {
u32 nr[SCOUTFS_BLOOM_BITS];
};
void scoutfs_calc_bloom_bits(struct scoutfs_bloom_bits *bits,
struct scoutfs_key *key, __le32 *salts);
void scoutfs_set_bloom_bits(struct scoutfs_bloom_block *blm, unsigned int nr,
struct scoutfs_bloom_bits *bits);
#endif