From 3e7ac6a3c698a28e9f0cd2b69b2a85f789524d96 Mon Sep 17 00:00:00 2001 From: Andre Noll Date: Sun, 21 Dec 2008 23:47:28 +0100 Subject: [PATCH] First draft of hard link detection via bloom filters. --- Makefile | 2 +- adu.ggo | 30 +++++++++ bloom.c | 183 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ bloom.h | 12 ++++ create.c | 127 +++++++++++++++++++++++++++++++++----- 5 files changed, 339 insertions(+), 15 deletions(-) create mode 100644 bloom.c create mode 100644 bloom.h diff --git a/Makefile b/Makefile index 0cce3b9..4832666 100644 --- a/Makefile +++ b/Makefile @@ -1,4 +1,4 @@ -objects := adu.o string.o cmdline.o fd.o select.o create.o interactive.o select.cmdline.o format.o user.o +objects := adu.o string.o cmdline.o fd.o select.o create.o interactive.o select.cmdline.o format.o user.o bloom.o all: adu version := 0.0.5 diff --git a/adu.ggo b/adu.ggo index 2ecdea4..84187eb 100644 --- a/adu.ggo +++ b/adu.ggo @@ -138,6 +138,36 @@ details=" users. Decreasing the value causes adu to use slightly less memory. " +option "bloom-filter-order" B +#~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +"use bloom filters for hard link detection" +int typestr="order" +dependon="create" +default="23" +optional +details=" + Allocate bloom filters of size 2^order bits. Each regular + file with hard link count greater than one is added to these + filters which allows to detect hard links on a per-user basis. + Greater values reduce the probability of false positives but + require more memory. + + Values less than 10 deactivate this feature so that no hard + links are being detected. +" + +option "num-bloom-filter-hash-functions" N +#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +"number of hash functions for the bloom filters" +int typestr="num" +dependon="create" +default="10" +optional +details=" + Cause each entry which is added to the bloom filter to set + \"num\" bits of the bloom filter. +" + ############################## section "Options for --select" ############################## diff --git a/bloom.c b/bloom.c new file mode 100644 index 0000000..f7a9b1a --- /dev/null +++ b/bloom.c @@ -0,0 +1,183 @@ +#include +#include +#include +#include +#include + +#include "adu.h" +#include "string.h" +#include "bloom.h" + +#ifdef TEST_BLOOM +void *adu_calloc(size_t size) +{ + void *ret = malloc(size); + memset(ret, 0, size); + return ret; +} +#undef INFO_LOG +#define INFO_LOG printf +#endif + +static inline uint64_t filter_bits(struct bloom *b) +{ + return 1ULL << b->order; +} + +/* + * SuperFastHash, by Paul Hsieh. + * http://www.azillionmonkeys.com/qed/hash.html + */ + +#if (defined(__GNUC__) && defined(__i386__)) +#define get16bits(d) (*((const uint16_t *) (d))) +#else +#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\ + +(uint32_t)(((const uint8_t *)(d))[0]) ) +#endif + + +static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash) +{ + uint32_t tmp; + int rem = len & 3; + + len >>= 2; + + for (;len > 0; len--) { + hash += get16bits (data); + tmp = (get16bits (data+2) << 11) ^ hash; + hash = (hash << 16) ^ tmp; + data += 2*sizeof (uint16_t); + hash += hash >> 11; + } + + /* Handle end cases */ + switch (rem) { + case 3: + hash += get16bits (data); + hash ^= hash << 16; + hash ^= data[sizeof (uint16_t)] << 18; + hash += hash >> 11; + break; + case 2: + hash += get16bits (data); + hash ^= hash << 11; + hash += hash >> 17; + break; + case 1: + hash += *data; + hash ^= hash << 10; + hash += hash >> 1; + } + /* Force "avalanching" of final 127 bits */ + hash ^= hash << 3; + hash += hash >> 5; + hash ^= hash << 4; + hash += hash >> 17; + hash ^= hash << 25; + hash += hash >> 6; + return hash; +} + +static int test_and_set_bit(uint64_t bitnum, struct bloom *b) +{ + uint64_t byte = bitnum / 8; + uint8_t bit = 1 << (bitnum % 8); + int ret = b->filter[byte] & bit; + + b->filter[byte] |= bit; + + if (!ret) + b->num_set_bits++; + return ret; +} + +int bloom_test_and_insert(const uint8_t *data, size_t len, struct bloom *b) +{ + int i, ret = 0; + uint32_t h = 0xb11924e1; /* some arbitrary value */ + + for (i = 1; i < b->num_hash_functions; i++) { + uint64_t bitnum = super_fast_hash(data, len, h); + h = bitnum; + if (b->order > 32) { + bitnum = bitnum << 32; + h = super_fast_hash(data, len, h); + bitnum |= h; + } + bitnum &= filter_bits(b) - 1; + ret |= !test_and_set_bit(bitnum, b); + } + if (ret) + b->num_entries++; + return !ret; +} + +int bloom_test_and_insert_string(const char *str, struct bloom *b) +{ + uint32_t len = strlen(str); + + return bloom_test_and_insert((const uint8_t *)str, len, b); +} + +void bloom_free(struct bloom *b) +{ + if (!b) + return; + free(b->filter); + free(b); +} + +int bloom_init(unsigned order, unsigned num_hash_functions, + struct bloom **result) +{ + struct bloom *b = adu_calloc(sizeof(*b)); + + INFO_LOG("allocating bloom filter (order: %u, %u hash functions)\n", + order, num_hash_functions); + b->order = order; + b->num_hash_functions = num_hash_functions; + b->filter = adu_calloc(filter_bits(b) / 8); + *result = b; + return 1; +} + +#ifdef TEST_BLOOM + +void add_stdin(struct bloom *b) +{ + char buf[255]; + unsigned false_positives = 0; + + while (fgets(buf, sizeof(buf) - 1, stdin)) { + size_t len = strlen(buf); + if (!len) + continue; + if (buf[len - 1] == '\n') + buf[len - 1] = '\0'; + if (bloom_test_and_insert_string(buf, b)) + false_positives++; + } + INFO_LOG("filter contains %llu entries\n", b->num_entries); + printf("%u possible false positives\n", false_positives); +} + +int main(int argc, char **argv) +{ + struct bloom *b; + + if (argc != 3) { + printf("usage: $0 j k\n"); + printf("j: set bloom filter size to m=2^j bits\n"); + printf("k: # of hash functions to use\n"); + exit(1); + } + bloom_init(atoi(argv[1]), atoi(argv[2]), &b); + add_stdin(b); + INFO_LOG("%u%% of bits are set\n", (unsigned) + (b->num_set_bits * 100ULL / filter_bits(b))); + return 1; +} + +#endif /* TEST_BLOOM */ diff --git a/bloom.h b/bloom.h new file mode 100644 index 0000000..afb2298 --- /dev/null +++ b/bloom.h @@ -0,0 +1,12 @@ +struct bloom { + unsigned order; + unsigned num_hash_functions; + uint64_t num_entries; + uint64_t num_set_bits; + uint8_t *filter; +}; + +int bloom_init(unsigned bloom_filter_order, unsigned num_hash_functions, + struct bloom **result); +void bloom_free(struct bloom *b); +int bloom_test_and_insert(const uint8_t *data, size_t len, struct bloom *b); diff --git a/create.c b/create.c index 87b0b9a..1b4ba88 100644 --- a/create.c +++ b/create.c @@ -15,9 +15,57 @@ #include "string.h" #include "error.h" #include "user.h" +#include "bloom.h" /* Id of the device containing the base dir. */ static dev_t device_id; +static struct bloom *global_bloom_filter; +static struct bloom *user_bloom_filter; + +static int consider_bloom(struct stat64 *s) +{ + if (!global_bloom_filter) + return 0; + if (s->st_nlink <= 1) + return 0; + return 1; +} + +#define GLOBAL_BLOOM_BUF_SIZE (sizeof(ino_t) + sizeof(dev_t) + sizeof(off_t)) +#define USER_BLOOM_BUF_SIZE (GLOBAL_BLOOM_BUF_SIZE + sizeof(uid_t)) + +static void make_bloom_buf(struct stat64 *s, uint8_t buf[USER_BLOOM_BUF_SIZE]) +{ + uint8_t *p = buf; + + if (!consider_bloom(s)) + return; + memcpy(p, &s->st_ino, sizeof(ino_t)); + p += sizeof(ino_t); + memcpy(p, &s->st_dev, sizeof(dev_t)); + p += sizeof(dev_t); + memcpy(p, &s->st_size, sizeof(off_t)); + p += sizeof(off_t); + memcpy(p, &s->st_uid, sizeof(uid_t)); +} + +static int insert_global_bloom(struct stat64 *s, + uint8_t buf[USER_BLOOM_BUF_SIZE]) +{ + if (!consider_bloom(s)) + return 0; + return bloom_test_and_insert(buf, GLOBAL_BLOOM_BUF_SIZE, + global_bloom_filter); +} + +static int insert_user_bloom(struct stat64 *s, + uint8_t buf[USER_BLOOM_BUF_SIZE]) +{ + if (!consider_bloom(s)) + return 0; + return bloom_test_and_insert(buf, USER_BLOOM_BUF_SIZE, + user_bloom_filter); +} static int add_directory(char *dirname, uint64_t *dir_num, uint64_t *parent_dir_num, uint64_t *dir_size, uint64_t *dir_files) @@ -39,7 +87,7 @@ static int add_directory(char *dirname, uint64_t *dir_num, uint64_t *parent_dir_ } static int update_user_row(struct osl_table *t, uint64_t dir_num, - uint64_t *add) + uint64_t add) { struct osl_row *row; struct osl_object obj = {.data = &dir_num, .size = sizeof(dir_num)}; @@ -54,8 +102,8 @@ static int update_user_row(struct osl_table *t, uint64_t dir_num, objects[UT_DIR_NUM].data = &dir_num; objects[UT_DIR_NUM].size = sizeof(dir_num); - objects[UT_BYTES].data = add; - objects[UT_BYTES].size = sizeof(*add); + objects[UT_BYTES].data = &add; + objects[UT_BYTES].size = sizeof(add); objects[UT_FILES].data = &num_files; objects[UT_FILES].size = sizeof(num_files); ret = osl(osl_add_row(t, objects)); @@ -67,7 +115,7 @@ static int update_user_row(struct osl_table *t, uint64_t dir_num, ret = osl(osl_get_object(t, row, UT_BYTES, &obj1)); if (ret < 0) return ret; - num = *(uint64_t *)obj1.data + *add; + num = *(uint64_t *)obj1.data + add; ret = osl(osl_update_object(t, row, UT_BYTES, &obj2)); if (ret < 0) return ret; @@ -87,7 +135,6 @@ static int scan_dir(char *dirname, uint64_t *parent_dir_num) uint64_t dir_size = 0, dir_files = 0; /* dir count. */ static uint64_t current_dir_num; - uint64_t this_dir_num = ++current_dir_num; check_signals(); @@ -102,9 +149,8 @@ static int scan_dir(char *dirname, uint64_t *parent_dir_num) while ((entry = readdir(dir))) { mode_t m; struct stat64 s; - uint32_t uid; - uint64_t size; struct user_info *ui; + uint8_t bloom_buf[USER_BLOOM_BUF_SIZE]; if (!strcmp(entry->d_name, ".")) continue; @@ -121,20 +167,38 @@ static int scan_dir(char *dirname, uint64_t *parent_dir_num) if (S_ISDIR(m)) { if (conf.one_file_system_given && s.st_dev != device_id) continue; + dir_size += s.st_size; + dir_files++; + ret = create_user_table(s.st_uid, &ui); + if (ret < 0) + goto out; + ret = update_user_row(ui->table, this_dir_num, + s.st_size); + if (ret < 0) + goto out; ret = scan_dir(entry->d_name, &this_dir_num); if (ret < 0) goto out; continue; } + /* regular file */ - size = s.st_size; - dir_size += size; + make_bloom_buf(&s, bloom_buf); + if (insert_global_bloom(&s, bloom_buf)) + DEBUG_LOG("global hard link: %s/%s\n", dirname, + entry->d_name); + else + dir_size += s.st_size; dir_files++; - uid = s.st_uid; - ret = create_user_table(uid, &ui); + ret = create_user_table(s.st_uid, &ui); if (ret < 0) goto out; - ret = update_user_row(ui->table, this_dir_num, &size); + ret = insert_user_bloom(&s, bloom_buf); + if (ret) + DEBUG_LOG("hard link for uid %d: %s/%s\n", + (unsigned)s.st_uid, dirname, entry->d_name); + ret = update_user_row(ui->table, this_dir_num, + ret? 0 : s.st_size); if (ret < 0) goto out; } @@ -149,6 +213,32 @@ out: return ret; } +static void log_bloom_stat(struct bloom *b) +{ + unsigned percent; + + NOTICE_LOG("\tfilter contains %llu entries\n", + (long long unsigned)b->num_entries); + percent = b->num_set_bits * 100ULL / (1ULL << b->order); + NOTICE_LOG("\t%u%% of bits are set\n", percent); + if (percent > 50) { + WARNING_LOG("results may be unreliable!\n"); + WARNING_LOG("consider incrasing bllom filter size\n"); + } +} + +static void log_bloom_stats(void) +{ + struct bloom *b = global_bloom_filter; + if (!b) + return; + NOTICE_LOG("global bloom filter statistics:\n"); + log_bloom_stat(b); + NOTICE_LOG("user bloom filter statistics:\n"); + b = user_bloom_filter; + log_bloom_stat(b); +} + /** * The main function of the create mode. * @@ -157,23 +247,32 @@ out: int com_create(void) { uint64_t zero = 0ULL; - int ret; + int ret, order = conf.bloom_filter_order_arg, + num = conf.num_bloom_filter_hash_functions_arg; struct stat statbuf; if (lstat(conf.base_dir_arg, &statbuf) == -1) return -ERRNO_TO_ERROR(errno); if (!S_ISDIR(statbuf.st_mode)) return -ERRNO_TO_ERROR(ENOTDIR); + if (order >= 10 && num > 0) { + bloom_init(order, num, &global_bloom_filter); + bloom_init(order, num, &user_bloom_filter); + } else + WARNING_LOG("hard link detection deactivated\n"); device_id = statbuf.st_dev; create_hash_table(conf.hash_table_bits_arg); ret = open_dir_table(1); if (ret < 0) - return ret; + goto out; check_signals(); ret = scan_dir(conf.base_dir_arg, &zero); if (ret < 0) goto out; ret = write_uid_file(); + log_bloom_stats(); out: + bloom_free(global_bloom_filter); + bloom_free(user_bloom_filter); return ret; } -- 2.39.5