/*
Trivial Database 2: free list/block handling
Copyright (C) Rusty Russell 2010
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see .
*/
#include "private.h"
#include
#include
#include
#include
static unsigned fls64(uint64_t val)
{
#if HAVE_BUILTIN_CLZL
if (val <= ULONG_MAX) {
/* This is significantly faster! */
return val ? sizeof(long) * CHAR_BIT - __builtin_clzl(val) : 0;
} else {
#endif
uint64_t r = 64;
if (!val)
return 0;
if (!(val & 0xffffffff00000000ull)) {
val <<= 32;
r -= 32;
}
if (!(val & 0xffff000000000000ull)) {
val <<= 16;
r -= 16;
}
if (!(val & 0xff00000000000000ull)) {
val <<= 8;
r -= 8;
}
if (!(val & 0xf000000000000000ull)) {
val <<= 4;
r -= 4;
}
if (!(val & 0xc000000000000000ull)) {
val <<= 2;
r -= 2;
}
if (!(val & 0x8000000000000000ull)) {
val <<= 1;
r -= 1;
}
return r;
#if HAVE_BUILTIN_CLZL
}
#endif
}
/* In which bucket would we find a particular record size? (ignoring header) */
unsigned int size_to_bucket(unsigned int zone_bits, tdb_len_t data_len)
{
unsigned int bucket;
/* We can't have records smaller than this. */
assert(data_len >= TDB_MIN_DATA_LEN);
/* Ignoring the header... */
if (data_len - TDB_MIN_DATA_LEN <= 64) {
/* 0 in bucket 0, 8 in bucket 1... 64 in bucket 8. */
bucket = (data_len - TDB_MIN_DATA_LEN) / 8;
} else {
/* After that we go power of 2. */
bucket = fls64(data_len - TDB_MIN_DATA_LEN) + 2;
}
if (unlikely(bucket > BUCKETS_FOR_ZONE(zone_bits)))
bucket = BUCKETS_FOR_ZONE(zone_bits);
return bucket;
}
/* Subtract 1-byte tailer and header. Then round up to next power of 2. */
static unsigned max_zone_bits(struct tdb_context *tdb)
{
return fls64(tdb->map_size-1-sizeof(struct tdb_header)-1) + 1;
}
/* Start by using a random zone to spread the load: returns the offset. */
static uint64_t random_zone(struct tdb_context *tdb)
{
struct free_zone_header zhdr;
tdb_off_t off = sizeof(struct tdb_header);
tdb_len_t half_bits;
uint64_t randbits = 0;
unsigned int i;
for (i = 0; i < 64; i += fls64(RAND_MAX))
randbits ^= ((uint64_t)random()) << i;
/* FIXME: Does this work? Test! */
half_bits = max_zone_bits(tdb) - 1;
do {
/* Pick left or right side (not outside file) */
if ((randbits & 1)
&& !tdb->methods->oob(tdb, off + (1ULL << half_bits)
+ sizeof(zhdr), true)) {
off += 1ULL << half_bits;
}
randbits >>= 1;
if (tdb_read_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
return TDB_OFF_ERR;
if (zhdr.zone_bits == half_bits)
return off;
half_bits--;
} while (half_bits >= INITIAL_ZONE_BITS);
tdb->ecode = TDB_ERR_CORRUPT;
tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
"random_zone: zone at %llu smaller than %u bits?",
(long long)off, INITIAL_ZONE_BITS);
return TDB_OFF_ERR;
}
int tdb_zone_init(struct tdb_context *tdb)
{
tdb->zone_off = random_zone(tdb);
if (tdb->zone_off == TDB_OFF_ERR)
return -1;
if (tdb_read_convert(tdb, tdb->zone_off,
&tdb->zhdr, sizeof(tdb->zhdr)) == -1)
return -1;
return 0;
}
/* Where's the header, given a zone size of 1 << zone_bits? */
static tdb_off_t zone_off(tdb_off_t off, unsigned int zone_bits)
{
off -= sizeof(struct tdb_header);
return (off & ~((1ULL << zone_bits) - 1)) + sizeof(struct tdb_header);
}
/* Offset of a given bucket. */
/* FIXME: bucket can be "unsigned" everywhere, or even uint8/16. */
tdb_off_t bucket_off(tdb_off_t zone_off, tdb_off_t bucket)
{
return zone_off
+ sizeof(struct free_zone_header)
+ bucket * sizeof(tdb_off_t);
}
/* Returns free_buckets + 1, or list number to search. */
static tdb_off_t find_free_head(struct tdb_context *tdb, tdb_off_t bucket)
{
/* Speculatively search for a non-zero bucket. */
return tdb_find_nonzero_off(tdb, bucket_off(tdb->zone_off, 0),
bucket,
BUCKETS_FOR_ZONE(tdb->zhdr.zone_bits) + 1);
}
/* Remove from free bucket. */
static int remove_from_list(struct tdb_context *tdb,
tdb_off_t b_off, struct tdb_free_record *r)
{
tdb_off_t off;
/* Front of list? */
if (r->prev == 0) {
off = b_off;
} else {
off = r->prev + offsetof(struct tdb_free_record, next);
}
/* r->prev->next = r->next */
if (tdb_write_off(tdb, off, r->next)) {
return -1;
}
if (r->next != 0) {
off = r->next + offsetof(struct tdb_free_record, prev);
/* r->next->prev = r->prev */
if (tdb_write_off(tdb, off, r->prev)) {
return -1;
}
}
return 0;
}
/* Enqueue in this free bucket. */
static int enqueue_in_free(struct tdb_context *tdb,
tdb_off_t b_off,
tdb_off_t off,
struct tdb_free_record *new)
{
new->prev = 0;
/* new->next = head. */
new->next = tdb_read_off(tdb, b_off);
if (new->next == TDB_OFF_ERR)
return -1;
if (new->next) {
/* next->prev = new. */
if (tdb_write_off(tdb, new->next
+ offsetof(struct tdb_free_record, prev),
off) != 0)
return -1;
}
/* head = new */
if (tdb_write_off(tdb, b_off, off) != 0)
return -1;
return tdb_write_convert(tdb, off, new, sizeof(*new));
}
/* List need not be locked. */
int add_free_record(struct tdb_context *tdb,
unsigned int zone_bits,
tdb_off_t off, tdb_len_t len_with_header)
{
struct tdb_free_record new;
tdb_off_t b_off;
int ret;
assert(len_with_header >= sizeof(new));
assert(zone_bits < (1 << 6));
new.magic_and_meta = TDB_FREE_MAGIC | zone_bits;
new.data_len = len_with_header - sizeof(struct tdb_used_record);
b_off = bucket_off(zone_off(off, zone_bits),
size_to_bucket(zone_bits, new.data_len));
if (tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT) != 0)
return -1;
ret = enqueue_in_free(tdb, b_off, off, &new);
tdb_unlock_free_bucket(tdb, b_off);
return ret;
}
/* If we have enough left over to be useful, split that off. */
static int to_used_record(struct tdb_context *tdb,
unsigned int zone_bits,
tdb_off_t off,
tdb_len_t needed,
tdb_len_t total_len,
tdb_len_t *actual)
{
struct tdb_used_record used;
tdb_len_t leftover;
leftover = total_len - needed;
if (leftover < sizeof(struct tdb_free_record))
leftover = 0;
*actual = total_len - leftover;
if (leftover) {
if (add_free_record(tdb, zone_bits,
off + sizeof(used) + *actual,
total_len - needed))
return -1;
}
return 0;
}
/* Note: we unlock the current bucket if we coalesce or fail. */
static int coalesce(struct tdb_context *tdb,
tdb_off_t zone_off, unsigned zone_bits,
tdb_off_t off, tdb_off_t b_off, tdb_len_t data_len)
{
struct tdb_free_record pad, *r;
tdb_off_t end = off + sizeof(struct tdb_used_record) + data_len;
while (end < (zone_off + (1ULL << zone_bits))) {
tdb_off_t nb_off;
/* FIXME: do tdb_get here and below really win? */
r = tdb_get(tdb, end, &pad, sizeof(pad));
if (!r)
goto err;
if (frec_magic(r) != TDB_FREE_MAGIC)
break;
nb_off = bucket_off(zone_off,
size_to_bucket(zone_bits, r->data_len));
/* We may be violating lock order here, so best effort. */
if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT) == -1)
break;
/* Now we have lock, re-check. */
r = tdb_get(tdb, end, &pad, sizeof(pad));
if (!r) {
tdb_unlock_free_bucket(tdb, nb_off);
goto err;
}
if (unlikely(frec_magic(r) != TDB_FREE_MAGIC)) {
tdb_unlock_free_bucket(tdb, nb_off);
break;
}
if (remove_from_list(tdb, nb_off, r) == -1) {
tdb_unlock_free_bucket(tdb, nb_off);
goto err;
}
end += sizeof(struct tdb_used_record) + r->data_len;
tdb_unlock_free_bucket(tdb, nb_off);
}
/* Didn't find any adjacent free? */
if (end == off + sizeof(struct tdb_used_record) + data_len)
return 0;
/* OK, expand record */
r = tdb_get(tdb, off, &pad, sizeof(pad));
if (!r)
goto err;
if (r->data_len != data_len) {
tdb->ecode = TDB_ERR_CORRUPT;
tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
"coalesce: expected data len %llu not %llu\n",
(long long)data_len, (long long)r->data_len);
goto err;
}
if (remove_from_list(tdb, b_off, r) == -1)
goto err;
/* We have to drop this to avoid deadlocks. */
tdb_unlock_free_bucket(tdb, b_off);
if (add_free_record(tdb, zone_bits, off, end - off) == -1)
return -1;
return 1;
err:
/* To unify error paths, we *always* unlock bucket on error. */
tdb_unlock_free_bucket(tdb, b_off);
return -1;
}
/* We need size bytes to put our key and data in. */
static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
tdb_off_t zone_off,
unsigned zone_bits,
tdb_off_t bucket,
size_t size,
tdb_len_t *actual)
{
tdb_off_t off, b_off,best_off;
struct tdb_free_record pad, best = { 0 }, *r;
double multiplier;
again:
b_off = bucket_off(zone_off, bucket);
/* FIXME: Try non-blocking wait first, to measure contention.
* If we're contented, try switching zones, and don't enlarge zone
* next time (we want more zones). */
/* Lock this bucket. */
if (tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT) == -1) {
return TDB_OFF_ERR;
}
best.data_len = -1ULL;
best_off = 0;
/* FIXME: Start with larger multiplier if we're growing. */
multiplier = 1.0;
/* Walk the list to see if any are large enough, getting less fussy
* as we go. */
off = tdb_read_off(tdb, b_off);
if (unlikely(off == TDB_OFF_ERR))
goto unlock_err;
while (off) {
/* FIXME: Does tdb_get win anything here? */
r = tdb_get(tdb, off, &pad, sizeof(*r));
if (!r)
goto unlock_err;
if (frec_magic(r) != TDB_FREE_MAGIC) {
tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
"lock_and_alloc: %llu non-free 0x%llx\n",
(long long)off, (long long)r->magic_and_meta);
goto unlock_err;
}
if (r->data_len >= size && r->data_len < best.data_len) {
best_off = off;
best = *r;
}
if (best.data_len < size * multiplier && best_off)
goto use_best;
multiplier *= 1.01;
/* Since we're going slow anyway, try coalescing here. */
switch (coalesce(tdb, zone_off, zone_bits, off, b_off,
r->data_len)) {
case -1:
/* This has already unlocked on error. */
return -1;
case 1:
/* This has unlocked list, restart. */
goto again;
}
off = r->next;
}
/* If we found anything at all, use it. */
if (best_off) {
use_best:
/* We're happy with this size: take it. */
if (remove_from_list(tdb, b_off, &best) != 0)
goto unlock_err;
tdb_unlock_free_bucket(tdb, b_off);
if (to_used_record(tdb, zone_bits, best_off, size,
best.data_len, actual)) {
return -1;
}
return best_off;
}
tdb_unlock_free_bucket(tdb, b_off);
return 0;
unlock_err:
tdb_unlock_free_bucket(tdb, b_off);
return TDB_OFF_ERR;
}
static bool next_zone(struct tdb_context *tdb)
{
tdb_off_t next = tdb->zone_off + (1ULL << tdb->zhdr.zone_bits);
/* We must have a header. */
if (tdb->methods->oob(tdb, next + sizeof(tdb->zhdr), true))
return false;
tdb->zone_off = next;
return tdb_read_convert(tdb, next, &tdb->zhdr, sizeof(tdb->zhdr)) == 0;
}
/* Offset returned is within current zone (which it may alter). */
static tdb_off_t get_free(struct tdb_context *tdb, size_t size,
tdb_len_t *actual)
{
tdb_off_t start_zone = tdb->zone_off, off;
bool wrapped = false;
/* FIXME: If we don't get a hit in the first bucket we want,
* try changing zones for next time. That should help wear
* zones evenly, so we don't need to search all of them before
* expanding. */
while (!wrapped || tdb->zone_off != start_zone) {
tdb_off_t b;
/* Shortcut for really huge allocations... */
if ((size >> tdb->zhdr.zone_bits) != 0)
continue;
/* Start at exact size bucket, and search up... */
b = size_to_bucket(tdb->zhdr.zone_bits, size);
for (b = find_free_head(tdb, b);
b <= BUCKETS_FOR_ZONE(tdb->zhdr.zone_bits);
b += find_free_head(tdb, b + 1)) {
/* Try getting one from list. */
off = lock_and_alloc(tdb, tdb->zone_off,
tdb->zhdr.zone_bits,
b, size, actual);
if (off == TDB_OFF_ERR)
return TDB_OFF_ERR;
if (off != 0)
return off;
/* Didn't work. Try next bucket. */
}
/* Didn't work, try next zone, if it exists. */
if (!next_zone(tdb)) {
wrapped = true;
tdb->zone_off = sizeof(struct tdb_header);
if (tdb_read_convert(tdb, tdb->zone_off,
&tdb->zhdr, sizeof(tdb->zhdr))) {
return TDB_OFF_ERR;
}
}
}
return 0;
}
int set_header(struct tdb_context *tdb,
struct tdb_used_record *rec,
uint64_t keylen, uint64_t datalen,
uint64_t actuallen, uint64_t hash,
unsigned int zone_bits)
{
uint64_t keybits = (fls64(keylen) + 1) / 2;
/* Use bottom bits of hash, so it's independent of hash table size. */
rec->magic_and_meta
= zone_bits
| ((hash & ((1 << 5)-1)) << 6)
| ((actuallen - (keylen + datalen)) << 11)
| (keybits << 43)
| (TDB_MAGIC << 48);
rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
/* Encoding can fail on big values. */
if (rec_key_length(rec) != keylen
|| rec_data_length(rec) != datalen
|| rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
tdb->ecode = TDB_ERR_IO;
tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
"Could not encode k=%llu,d=%llu,a=%llu\n",
(long long)keylen, (long long)datalen,
(long long)actuallen);
return -1;
}
return 0;
}
static bool zones_happy(struct tdb_context *tdb)
{
/* FIXME: look at distribution of zones. */
return true;
}
/* Assume we want buckets up to the comfort factor. */
static tdb_len_t overhead(unsigned int zone_bits)
{
return sizeof(struct free_zone_header)
+ (BUCKETS_FOR_ZONE(zone_bits) + 1) * sizeof(tdb_off_t);
}
/* Expand the database (by adding a zone). */
static int tdb_expand(struct tdb_context *tdb, tdb_len_t size)
{
uint64_t old_size;
tdb_off_t off;
uint8_t zone_bits;
unsigned int num_buckets;
tdb_len_t wanted;
struct free_zone_header zhdr;
bool enlarge_zone;
/* We need room for the record header too. */
wanted = sizeof(struct tdb_used_record) + size;
/* Only one person can expand file at a time. */
if (tdb_lock_expand(tdb, F_WRLCK) != 0)
return -1;
/* Someone else may have expanded the file, so retry. */
old_size = tdb->map_size;
tdb->methods->oob(tdb, tdb->map_size + 1, true);
if (tdb->map_size != old_size)
goto success;
/* FIXME: Tailer is a bogus optimization, remove it. */
/* zone bits tailer char is protected by EXPAND lock. */
if (tdb->methods->read(tdb, old_size - 1, &zone_bits, 1) == -1)
goto fail;
/* If zones aren't working well, add larger zone if possible. */
enlarge_zone = !zones_happy(tdb);
/* New zone can be between zone_bits or larger if we're on the right
* boundary. */
for (;;) {
/* Does this fit the allocation comfortably? */
if ((1ULL << zone_bits) >= overhead(zone_bits) + wanted) {
/* Only let enlarge_zone enlarge us once. */
if (!enlarge_zone)
break;
enlarge_zone = false;
}
if ((old_size - 1 - sizeof(struct tdb_header))
& (1 << zone_bits))
break;
zone_bits++;
}
zhdr.zone_bits = zone_bits;
num_buckets = BUCKETS_FOR_ZONE(zone_bits);
/* FIXME: I don't think we need to expand to full zone, do we? */
if (tdb->methods->expand_file(tdb, 1ULL << zone_bits) == -1)
goto fail;
/* Write new tailer. */
if (tdb->methods->write(tdb, tdb->map_size - 1, &zone_bits, 1) == -1)
goto fail;
/* Write new zone header (just before old tailer). */
off = old_size - 1;
if (tdb_write_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
goto fail;
/* Now write empty buckets. */
off += sizeof(zhdr);
if (zero_out(tdb, off, (num_buckets+1) * sizeof(tdb_off_t)) == -1)
goto fail;
off += (num_buckets+1) * sizeof(tdb_off_t);
/* Now add the rest as our free record. */
if (add_free_record(tdb, zone_bits, off, tdb->map_size-1-off) == -1)
goto fail;
/* Try allocating from this zone now. */
tdb->zone_off = old_size - 1;
tdb->zhdr = zhdr;
success:
tdb_unlock_expand(tdb, F_WRLCK);
return 0;
fail:
tdb_unlock_expand(tdb, F_WRLCK);
return -1;
}
static tdb_len_t adjust_size(size_t keylen, size_t datalen, bool growing)
{
tdb_len_t size = keylen + datalen;
if (size < TDB_MIN_DATA_LEN)
size = TDB_MIN_DATA_LEN;
/* Overallocate if this is coming from an enlarging store. */
if (growing)
size += datalen / 2;
/* Round to next uint64_t boundary. */
return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
}
/* This won't fail: it will expand the database if it has to. */
tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
uint64_t hash, bool growing)
{
tdb_off_t off;
tdb_len_t size, actual;
struct tdb_used_record rec;
/* We can't hold pointers during this: we could unmap! */
assert(!tdb->direct_access);
size = adjust_size(keylen, datalen, growing);
again:
off = get_free(tdb, size, &actual);
if (unlikely(off == TDB_OFF_ERR))
return off;
if (unlikely(off == 0)) {
if (tdb_expand(tdb, size) == -1)
return TDB_OFF_ERR;
goto again;
}
/* Some supergiant values can't be encoded. */
/* FIXME: Check before, and limit actual in get_free. */
if (set_header(tdb, &rec, keylen, datalen, actual, hash,
tdb->zhdr.zone_bits) != 0) {
add_free_record(tdb, tdb->zhdr.zone_bits, off,
sizeof(rec) + actual);
return TDB_OFF_ERR;
}
if (tdb_write_convert(tdb, off, &rec, sizeof(rec)) != 0)
return TDB_OFF_ERR;
return off;
}