+++ /dev/null
- /*
- Unix SMB/CIFS implementation.
-
- trivial database library
-
- Copyright (C) Andrew Tridgell 1999-2005
- Copyright (C) Paul `Rusty' Russell 2000
- Copyright (C) Jeremy Allison 2000-2003
-
- ** NOTE! The following LGPL license applies to the tdb
- ** library. This does NOT imply that all of Samba is released
- ** under the LGPL
-
- 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 <http://www.gnu.org/licenses/>.
-*/
-
-#include "tdb_private.h"
-
-/* 'right' merges can involve O(n^2) cost when combined with a
- traverse, so they are disabled until we find a way to do them in
- O(1) time
-*/
-#define USE_RIGHT_MERGES 0
-
-/* read a freelist record and check for simple errors */
-int tdb_rec_free_read(struct tdb_context *tdb, tdb_off_t off, struct tdb_record *rec)
-{
- if (tdb->methods->tdb_read(tdb, off, rec, sizeof(*rec),DOCONV()) == -1)
- return -1;
-
- if (rec->magic == TDB_MAGIC) {
- /* this happens when a app is showdown while deleting a record - we should
- not completely fail when this happens */
- TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_rec_free_read non-free magic 0x%x at offset=%d - fixing\n",
- rec->magic, off));
- rec->magic = TDB_FREE_MAGIC;
- if (tdb->methods->tdb_write(tdb, off, rec, sizeof(*rec)) == -1)
- return -1;
- }
-
- if (rec->magic != TDB_FREE_MAGIC) {
- /* Ensure ecode is set for log fn. */
- tdb->ecode = TDB_ERR_CORRUPT;
- TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_rec_free_read bad magic 0x%x at offset=%d\n",
- rec->magic, off));
- return -1;
- }
- if (tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 0) != 0)
- return -1;
- return 0;
-}
-
-
-#if USE_RIGHT_MERGES
-/* Remove an element from the freelist. Must have alloc lock. */
-static int remove_from_freelist(struct tdb_context *tdb, tdb_off_t off, tdb_off_t next)
-{
- tdb_off_t last_ptr, i;
-
- /* read in the freelist top */
- last_ptr = FREELIST_TOP;
- while (tdb_ofs_read(tdb, last_ptr, &i) != -1 && i != 0) {
- if (i == off) {
- /* We've found it! */
- return tdb_ofs_write(tdb, last_ptr, &next);
- }
- /* Follow chain (next offset is at start of record) */
- last_ptr = i;
- }
- tdb->ecode = TDB_ERR_CORRUPT;
- TDB_LOG((tdb, TDB_DEBUG_FATAL,"remove_from_freelist: not on list at off=%d\n", off));
- return -1;
-}
-#endif
-
-
-/* update a record tailer (must hold allocation lock) */
-static int update_tailer(struct tdb_context *tdb, tdb_off_t offset,
- const struct tdb_record *rec)
-{
- tdb_off_t totalsize;
-
- /* Offset of tailer from record header */
- totalsize = sizeof(*rec) + rec->rec_len;
- return tdb_ofs_write(tdb, offset + totalsize - sizeof(tdb_off_t),
- &totalsize);
-}
-
-/* Add an element into the freelist. Merge adjacent records if
- necessary. */
-int tdb_free(struct tdb_context *tdb, tdb_off_t offset, struct tdb_record *rec)
-{
- /* Allocation and tailer lock */
- if (tdb_lock(tdb, -1, F_WRLCK) != 0)
- return -1;
-
- /* set an initial tailer, so if we fail we don't leave a bogus record */
- if (update_tailer(tdb, offset, rec) != 0) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed!\n"));
- goto fail;
- }
-
-#if USE_RIGHT_MERGES
- /* Look right first (I'm an Australian, dammit) */
- if (offset + sizeof(*rec) + rec->rec_len + sizeof(*rec) <= tdb->map_size) {
- tdb_off_t right = offset + sizeof(*rec) + rec->rec_len;
- struct tdb_record r;
-
- if (tdb->methods->tdb_read(tdb, right, &r, sizeof(r), DOCONV()) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: right read failed at %u\n", right));
- goto left;
- }
-
- /* If it's free, expand to include it. */
- if (r.magic == TDB_FREE_MAGIC) {
- if (remove_from_freelist(tdb, right, r.next) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: right free failed at %u\n", right));
- goto left;
- }
- rec->rec_len += sizeof(r) + r.rec_len;
- if (update_tailer(tdb, offset, rec) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
- goto fail;
- }
- }
- }
-left:
-#endif
-
- /* Look left */
- if (offset - sizeof(tdb_off_t) > TDB_DATA_START(tdb->header.hash_size)) {
- tdb_off_t left = offset - sizeof(tdb_off_t);
- struct tdb_record l;
- tdb_off_t leftsize;
-
- /* Read in tailer and jump back to header */
- if (tdb_ofs_read(tdb, left, &leftsize) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left offset read failed at %u\n", left));
- goto update;
- }
-
- /* it could be uninitialised data */
- if (leftsize == 0 || leftsize == TDB_PAD_U32) {
- goto update;
- }
-
- left = offset - leftsize;
-
- if (leftsize > offset ||
- left < TDB_DATA_START(tdb->header.hash_size)) {
- goto update;
- }
-
- /* Now read in the left record */
- if (tdb->methods->tdb_read(tdb, left, &l, sizeof(l), DOCONV()) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left read failed at %u (%u)\n", left, leftsize));
- goto update;
- }
-
- /* If it's free, expand to include it. */
- if (l.magic == TDB_FREE_MAGIC) {
- /* we now merge the new record into the left record, rather than the other
- way around. This makes the operation O(1) instead of O(n). This change
- prevents traverse from being O(n^2) after a lot of deletes */
- l.rec_len += sizeof(*rec) + rec->rec_len;
- if (tdb_rec_write(tdb, left, &l) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_left failed at %u\n", left));
- goto fail;
- }
- if (update_tailer(tdb, left, &l) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
- goto fail;
- }
- tdb_unlock(tdb, -1, F_WRLCK);
- return 0;
- }
- }
-
-update:
-
- /* Now, prepend to free list */
- rec->magic = TDB_FREE_MAGIC;
-
- if (tdb_ofs_read(tdb, FREELIST_TOP, &rec->next) == -1 ||
- tdb_rec_write(tdb, offset, rec) == -1 ||
- tdb_ofs_write(tdb, FREELIST_TOP, &offset) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free record write failed at offset=%d\n", offset));
- goto fail;
- }
-
- /* And we're done. */
- tdb_unlock(tdb, -1, F_WRLCK);
- return 0;
-
- fail:
- tdb_unlock(tdb, -1, F_WRLCK);
- return -1;
-}
-
-
-
-/*
- the core of tdb_allocate - called when we have decided which
- free list entry to use
-
- Note that we try to allocate by grabbing data from the end of an existing record,
- not the beginning. This is so the left merge in a free is more likely to be
- able to free up the record without fragmentation
- */
-static tdb_off_t tdb_allocate_ofs(struct tdb_context *tdb,
- tdb_len_t length, tdb_off_t rec_ptr,
- struct tdb_record *rec, tdb_off_t last_ptr)
-{
-#define MIN_REC_SIZE (sizeof(struct tdb_record) + sizeof(tdb_off_t) + 8)
-
- if (rec->rec_len < length + MIN_REC_SIZE) {
- /* we have to grab the whole record */
-
- /* unlink it from the previous record */
- if (tdb_ofs_write(tdb, last_ptr, &rec->next) == -1) {
- return 0;
- }
-
- /* mark it not free */
- rec->magic = TDB_MAGIC;
- if (tdb_rec_write(tdb, rec_ptr, rec) == -1) {
- return 0;
- }
- return rec_ptr;
- }
-
- /* we're going to just shorten the existing record */
- rec->rec_len -= (length + sizeof(*rec));
- if (tdb_rec_write(tdb, rec_ptr, rec) == -1) {
- return 0;
- }
- if (update_tailer(tdb, rec_ptr, rec) == -1) {
- return 0;
- }
-
- /* and setup the new record */
- rec_ptr += sizeof(*rec) + rec->rec_len;
-
- memset(rec, '\0', sizeof(*rec));
- rec->rec_len = length;
- rec->magic = TDB_MAGIC;
-
- if (tdb_rec_write(tdb, rec_ptr, rec) == -1) {
- return 0;
- }
-
- if (update_tailer(tdb, rec_ptr, rec) == -1) {
- return 0;
- }
-
- return rec_ptr;
-}
-
-/* allocate some space from the free list. The offset returned points
- to a unconnected tdb_record within the database with room for at
- least length bytes of total data
-
- 0 is returned if the space could not be allocated
- */
-tdb_off_t tdb_allocate(struct tdb_context *tdb, tdb_len_t length, struct tdb_record *rec)
-{
- tdb_off_t rec_ptr, last_ptr, newrec_ptr;
- struct {
- tdb_off_t rec_ptr, last_ptr;
- tdb_len_t rec_len;
- } bestfit;
- float multiplier = 1.0;
-
- if (tdb_lock(tdb, -1, F_WRLCK) == -1)
- return 0;
-
- /* over-allocate to reduce fragmentation */
- length *= 1.25;
-
- /* Extra bytes required for tailer */
- length += sizeof(tdb_off_t);
- length = TDB_ALIGN(length, TDB_ALIGNMENT);
-
- again:
- last_ptr = FREELIST_TOP;
-
- /* read in the freelist top */
- if (tdb_ofs_read(tdb, FREELIST_TOP, &rec_ptr) == -1)
- goto fail;
-
- bestfit.rec_ptr = 0;
- bestfit.last_ptr = 0;
- bestfit.rec_len = 0;
-
- /*
- this is a best fit allocation strategy. Originally we used
- a first fit strategy, but it suffered from massive fragmentation
- issues when faced with a slowly increasing record size.
- */
- while (rec_ptr) {
- if (tdb_rec_free_read(tdb, rec_ptr, rec) == -1) {
- goto fail;
- }
-
- if (rec->rec_len >= length) {
- if (bestfit.rec_ptr == 0 ||
- rec->rec_len < bestfit.rec_len) {
- bestfit.rec_len = rec->rec_len;
- bestfit.rec_ptr = rec_ptr;
- bestfit.last_ptr = last_ptr;
- }
- }
-
- /* move to the next record */
- last_ptr = rec_ptr;
- rec_ptr = rec->next;
-
- /* if we've found a record that is big enough, then
- stop searching if its also not too big. The
- definition of 'too big' changes as we scan
- through */
- if (bestfit.rec_len > 0 &&
- bestfit.rec_len < length * multiplier) {
- break;
- }
-
- /* this multiplier means we only extremely rarely
- search more than 50 or so records. At 50 records we
- accept records up to 11 times larger than what we
- want */
- multiplier *= 1.05;
- }
-
- if (bestfit.rec_ptr != 0) {
- if (tdb_rec_free_read(tdb, bestfit.rec_ptr, rec) == -1) {
- goto fail;
- }
-
- newrec_ptr = tdb_allocate_ofs(tdb, length, bestfit.rec_ptr,
- rec, bestfit.last_ptr);
- tdb_unlock(tdb, -1, F_WRLCK);
- return newrec_ptr;
- }
-
- /* we didn't find enough space. See if we can expand the
- database and if we can then try again */
- if (tdb_expand(tdb, length + sizeof(*rec)) == 0)
- goto again;
- fail:
- tdb_unlock(tdb, -1, F_WRLCK);
- return 0;
-}
-
-
-
-/*
- return the size of the freelist - used to decide if we should repack
-*/
-int tdb_freelist_size(struct tdb_context *tdb)
-{
- tdb_off_t ptr;
- int count=0;
-
- if (tdb_lock(tdb, -1, F_RDLCK) == -1) {
- return -1;
- }
-
- ptr = FREELIST_TOP;
- while (tdb_ofs_read(tdb, ptr, &ptr) == 0 && ptr != 0) {
- count++;
- }
-
- tdb_unlock(tdb, -1, F_RDLCK);
- return count;
-}
projects / ccan / blobdiff