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authorVolker Lendecke <vlendec@samba.org>2006-08-18 16:25:09 +0000
committerGerald (Jerry) Carter <jerry@samba.org>2007-10-10 11:38:42 -0500
commit986461b6be03eefd3bd9d9c5f5921e14189813b2 (patch)
treef0a6fba525638e901ac09024728d44253b48de43 /source3/tdb/common/freelist.c
parent41a4496b20e510dc47fe2b816196cef6fe937cea (diff)
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r17607: Adapt the Samba4 directory structure for tdb. Makes it easier to diff.
Let's see what it breaks. For me it works :-) Volker (This used to be commit 337be14b432e5dfd80c7418b2db4fe0087259b77)
Diffstat (limited to 'source3/tdb/common/freelist.c')
-rw-r--r--source3/tdb/common/freelist.c331
1 files changed, 331 insertions, 0 deletions
diff --git a/source3/tdb/common/freelist.c b/source3/tdb/common/freelist.c
new file mode 100644
index 0000000000..3483751164
--- /dev/null
+++ b/source3/tdb/common/freelist.c
@@ -0,0 +1,331 @@
+ /*
+ 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 2 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, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include "tdb_private.h"
+
+/* read a freelist record and check for simple errors */
+static int rec_free_read(struct tdb_context *tdb, tdb_off_t off, struct list_struct *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, 0,"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, 0,"rec_free_read bad magic 0x%x at offset=%d\n",
+ rec->magic, off));
+ return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+ }
+ if (tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 0) != 0)
+ return -1;
+ return 0;
+}
+
+
+
+/* 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_LOG((tdb, 0,"remove_from_freelist: not on list at off=%d\n", off));
+ return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
+}
+
+
+/* update a record tailer (must hold allocation lock) */
+static int update_tailer(struct tdb_context *tdb, tdb_off_t offset,
+ const struct list_struct *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
+ neccessary. */
+int tdb_free(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec)
+{
+ tdb_off_t right, left;
+
+ /* 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, 0, "tdb_free: upfate_tailer failed!\n"));
+ goto fail;
+ }
+
+ /* Look right first (I'm an Australian, dammit) */
+ right = offset + sizeof(*rec) + rec->rec_len;
+ if (right + sizeof(*rec) <= tdb->map_size) {
+ struct list_struct r;
+
+ if (tdb->methods->tdb_read(tdb, right, &r, sizeof(r), DOCONV()) == -1) {
+ TDB_LOG((tdb, 0, "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, 0, "tdb_free: right free failed at %u\n", right));
+ goto left;
+ }
+ rec->rec_len += sizeof(r) + r.rec_len;
+ }
+ }
+
+left:
+ /* Look left */
+ left = offset - sizeof(tdb_off_t);
+ if (left > TDB_DATA_START(tdb->header.hash_size)) {
+ struct list_struct l;
+ tdb_off_t leftsize;
+
+ /* Read in tailer and jump back to header */
+ if (tdb_ofs_read(tdb, left, &leftsize) == -1) {
+ TDB_LOG((tdb, 0, "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;
+
+ /* Now read in record */
+ if (tdb->methods->tdb_read(tdb, left, &l, sizeof(l), DOCONV()) == -1) {
+ TDB_LOG((tdb, 0, "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) {
+ if (remove_from_freelist(tdb, left, l.next) == -1) {
+ TDB_LOG((tdb, 0, "tdb_free: left free failed at %u\n", left));
+ goto update;
+ } else {
+ offset = left;
+ rec->rec_len += leftsize;
+ }
+ }
+ }
+
+update:
+ if (update_tailer(tdb, offset, rec) == -1) {
+ TDB_LOG((tdb, 0, "tdb_free: update_tailer failed at %u\n", offset));
+ goto fail;
+ }
+
+ /* 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, 0, "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
+ */
+static tdb_off_t tdb_allocate_ofs(struct tdb_context *tdb, tdb_len_t length, tdb_off_t rec_ptr,
+ struct list_struct *rec, tdb_off_t last_ptr)
+{
+ struct list_struct newrec;
+ tdb_off_t newrec_ptr;
+
+ memset(&newrec, '\0', sizeof(newrec));
+
+ /* found it - now possibly split it up */
+ if (rec->rec_len > length + MIN_REC_SIZE) {
+ /* Length of left piece */
+ length = TDB_ALIGN(length, TDB_ALIGNMENT);
+
+ /* Right piece to go on free list */
+ newrec.rec_len = rec->rec_len - (sizeof(*rec) + length);
+ newrec_ptr = rec_ptr + sizeof(*rec) + length;
+
+ /* And left record is shortened */
+ rec->rec_len = length;
+ } else {
+ newrec_ptr = 0;
+ }
+
+ /* Remove allocated record from the free list */
+ if (tdb_ofs_write(tdb, last_ptr, &rec->next) == -1) {
+ return 0;
+ }
+
+ /* Update header: do this before we drop alloc
+ lock, otherwise tdb_free() might try to
+ merge with us, thinking we're free.
+ (Thanks Jeremy Allison). */
+ rec->magic = TDB_MAGIC;
+ if (tdb_rec_write(tdb, rec_ptr, rec) == -1) {
+ return 0;
+ }
+
+ /* Did we create new block? */
+ if (newrec_ptr) {
+ /* Update allocated record tailer (we
+ shortened it). */
+ if (update_tailer(tdb, rec_ptr, rec) == -1) {
+ return 0;
+ }
+
+ /* Free new record */
+ if (tdb_free(tdb, newrec_ptr, &newrec) == -1) {
+ return 0;
+ }
+ }
+
+ /* all done - return the new record offset */
+ return rec_ptr;
+}
+
+/* allocate some space from the free list. The offset returned points
+ to a unconnected list_struct 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 list_struct *rec)
+{
+ tdb_off_t rec_ptr, last_ptr, newrec_ptr;
+ struct {
+ tdb_off_t rec_ptr, last_ptr;
+ tdb_len_t rec_len;
+ } bestfit;
+
+ if (tdb_lock(tdb, -1, F_WRLCK) == -1)
+ return 0;
+
+ /* Extra bytes required for tailer */
+ length += sizeof(tdb_off_t);
+
+ 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 (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;
+ /* consider a fit to be good enough if
+ we aren't wasting more than half
+ the space */
+ if (bestfit.rec_len < 2*length) {
+ break;
+ }
+ }
+ }
+
+ /* move to the next record */
+ last_ptr = rec_ptr;
+ rec_ptr = rec->next;
+ }
+
+ if (bestfit.rec_ptr != 0) {
+ if (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;
+}
+