summaryrefslogtreecommitdiff
path: root/source4/lib/tdb/common/transaction.c
diff options
context:
space:
mode:
Diffstat (limited to 'source4/lib/tdb/common/transaction.c')
-rw-r--r--source4/lib/tdb/common/transaction.c976
1 files changed, 976 insertions, 0 deletions
diff --git a/source4/lib/tdb/common/transaction.c b/source4/lib/tdb/common/transaction.c
new file mode 100644
index 0000000000..b9d44a7283
--- /dev/null
+++ b/source4/lib/tdb/common/transaction.c
@@ -0,0 +1,976 @@
+ /*
+ Unix SMB/CIFS implementation.
+
+ trivial database library
+
+ Copyright (C) Andrew Tridgell 2005
+
+ ** 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"
+
+/*
+ transaction design:
+
+ - only allow a single transaction at a time per database. This makes
+ using the transaction API simpler, as otherwise the caller would
+ have to cope with temporary failures in transactions that conflict
+ with other current transactions
+
+ - keep the transaction recovery information in the same file as the
+ database, using a special 'transaction recovery' record pointed at
+ by the header. This removes the need for extra journal files as
+ used by some other databases
+
+ - dymacially allocated the transaction recover record, re-using it
+ for subsequent transactions. If a larger record is needed then
+ tdb_free() the old record to place it on the normal tdb freelist
+ before allocating the new record
+
+ - during transactions, keep a linked list of writes all that have
+ been performed by intercepting all tdb_write() calls. The hooked
+ transaction versions of tdb_read() and tdb_write() check this
+ linked list and try to use the elements of the list in preference
+ to the real database.
+
+ - don't allow any locks to be held when a transaction starts,
+ otherwise we can end up with deadlock (plus lack of lock nesting
+ in posix locks would mean the lock is lost)
+
+ - if the caller gains a lock during the transaction but doesn't
+ release it then fail the commit
+
+ - allow for nested calls to tdb_transaction_start(), re-using the
+ existing transaction record. If the inner transaction is cancelled
+ then a subsequent commit will fail
+
+ - keep a mirrored copy of the tdb hash chain heads to allow for the
+ fast hash heads scan on traverse, updating the mirrored copy in
+ the transaction version of tdb_write
+
+ - allow callers to mix transaction and non-transaction use of tdb,
+ although once a transaction is started then an exclusive lock is
+ gained until the transaction is committed or cancelled
+
+ - the commit stategy involves first saving away all modified data
+ into a linearised buffer in the transaction recovery area, then
+ marking the transaction recovery area with a magic value to
+ indicate a valid recovery record. In total 4 fsync/msync calls are
+ needed per commit to prevent race conditions. It might be possible
+ to reduce this to 3 or even 2 with some more work.
+
+ - check for a valid recovery record on open of the tdb, while the
+ global lock is held. Automatically recover from the transaction
+ recovery area if needed, then continue with the open as
+ usual. This allows for smooth crash recovery with no administrator
+ intervention.
+
+ - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
+ still available, but no transaction recovery area is used and no
+ fsync/msync calls are made.
+
+*/
+
+
+/*
+ hold the context of any current transaction
+*/
+struct tdb_transaction {
+ /* we keep a mirrored copy of the tdb hash heads here so
+ tdb_next_hash_chain() can operate efficiently */
+ u32 *hash_heads;
+
+ /* the original io methods - used to do IOs to the real db */
+ const struct tdb_methods *io_methods;
+
+ /* the list of transaction elements. We use a doubly linked
+ list with a last pointer to allow us to keep the list
+ ordered, with first element at the front of the list. It
+ needs to be doubly linked as the read/write traversals need
+ to be backwards, while the commit needs to be forwards */
+ struct tdb_transaction_el {
+ struct tdb_transaction_el *next, *prev;
+ tdb_off_t offset;
+ tdb_len_t length;
+ unsigned char *data;
+ } *elements, *elements_last;
+
+ /* non-zero when an internal transaction error has
+ occurred. All write operations will then fail until the
+ transaction is ended */
+ int transaction_error;
+
+ /* when inside a transaction we need to keep track of any
+ nested tdb_transaction_start() calls, as these are allowed,
+ but don't create a new transaction */
+ int nesting;
+
+ /* old file size before transaction */
+ tdb_len_t old_map_size;
+};
+
+
+/*
+ read while in a transaction. We need to check first if the data is in our list
+ of transaction elements, then if not do a real read
+*/
+static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
+ tdb_len_t len, int cv)
+{
+ struct tdb_transaction_el *el;
+
+ /* we need to walk the list backwards to get the most recent data */
+ for (el=tdb->transaction->elements_last;el;el=el->prev) {
+ tdb_len_t partial;
+
+ if (off+len <= el->offset) {
+ continue;
+ }
+ if (off >= el->offset + el->length) {
+ continue;
+ }
+
+ /* an overlapping read - needs to be split into up to
+ 2 reads and a memcpy */
+ if (off < el->offset) {
+ partial = el->offset - off;
+ if (transaction_read(tdb, off, buf, partial, cv) != 0) {
+ goto fail;
+ }
+ len -= partial;
+ off += partial;
+ buf = (void *)(partial + (char *)buf);
+ }
+ if (off + len <= el->offset + el->length) {
+ partial = len;
+ } else {
+ partial = el->offset + el->length - off;
+ }
+ memcpy(buf, el->data + (off - el->offset), partial);
+ if (cv) {
+ tdb_convert(buf, len);
+ }
+ len -= partial;
+ off += partial;
+ buf = (void *)(partial + (char *)buf);
+
+ if (len != 0 && transaction_read(tdb, off, buf, len, cv) != 0) {
+ goto fail;
+ }
+
+ return 0;
+ }
+
+ /* its not in the transaction elements - do a real read */
+ return tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv);
+
+fail:
+ TDB_LOG((tdb, 0, "transaction_read: failed at off=%d len=%d\n", off, len));
+ tdb->ecode = TDB_ERR_IO;
+ tdb->transaction->transaction_error = 1;
+ return -1;
+}
+
+
+/*
+ write while in a transaction
+*/
+static int transaction_write(struct tdb_context *tdb, tdb_off_t off,
+ const void *buf, tdb_len_t len)
+{
+ struct tdb_transaction_el *el;
+
+ /* if the write is to a hash head, then update the transaction
+ hash heads */
+ if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
+ off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
+ u32 chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
+ memcpy(&tdb->transaction->hash_heads[chain], buf, len);
+ }
+
+ /* first see if we can replace an existing entry */
+ for (el=tdb->transaction->elements_last;el;el=el->prev) {
+ tdb_len_t partial;
+
+ if (off+len <= el->offset) {
+ continue;
+ }
+ if (off >= el->offset + el->length) {
+ continue;
+ }
+
+ /* an overlapping write - needs to be split into up to
+ 2 writes and a memcpy */
+ if (off < el->offset) {
+ partial = el->offset - off;
+ if (transaction_write(tdb, off, buf, partial) != 0) {
+ goto fail;
+ }
+ len -= partial;
+ off += partial;
+ buf = (const void *)(partial + (const char *)buf);
+ }
+ if (off + len <= el->offset + el->length) {
+ partial = len;
+ } else {
+ partial = el->offset + el->length - off;
+ }
+ memcpy(el->data + (off - el->offset), buf, partial);
+ len -= partial;
+ off += partial;
+ buf = (const void *)(partial + (const char *)buf);
+
+ if (len != 0 && transaction_write(tdb, off, buf, len) != 0) {
+ goto fail;
+ }
+
+ return 0;
+ }
+
+ /* add a new entry at the end of the list */
+ el = malloc(sizeof(*el));
+ if (el == NULL) {
+ tdb->ecode = TDB_ERR_OOM;
+ tdb->transaction->transaction_error = 1;
+ return -1;
+ }
+ el->next = NULL;
+ el->prev = tdb->transaction->elements_last;
+ el->offset = off;
+ el->length = len;
+ el->data = malloc(len);
+ if (el->data == NULL) {
+ free(el);
+ tdb->ecode = TDB_ERR_OOM;
+ tdb->transaction->transaction_error = 1;
+ return -1;
+ }
+ if (buf) {
+ memcpy(el->data, buf, len);
+ } else {
+ memset(el->data, TDB_PAD_BYTE, len);
+ }
+ if (el->prev) {
+ el->prev->next = el;
+ } else {
+ tdb->transaction->elements = el;
+ }
+ tdb->transaction->elements_last = el;
+ return 0;
+
+fail:
+ TDB_LOG((tdb, 0, "transaction_write: failed at off=%d len=%d\n", off, len));
+ tdb->ecode = TDB_ERR_IO;
+ tdb->transaction->transaction_error = 1;
+ return -1;
+}
+
+/*
+ accelerated hash chain head search, using the cached hash heads
+*/
+static void transaction_next_hash_chain(struct tdb_context *tdb, u32 *chain)
+{
+ u32 h = *chain;
+ for (;h < tdb->header.hash_size;h++) {
+ /* the +1 takes account of the freelist */
+ if (0 != tdb->transaction->hash_heads[h+1]) {
+ break;
+ }
+ }
+ (*chain) = h;
+}
+
+/*
+ out of bounds check during a transaction
+*/
+static int transaction_oob(struct tdb_context *tdb, tdb_off_t len, int probe)
+{
+ if (len <= tdb->map_size) {
+ return 0;
+ }
+ return TDB_ERRCODE(TDB_ERR_IO, -1);
+}
+
+/*
+ transaction version of tdb_expand().
+*/
+static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
+ tdb_off_t addition)
+{
+ /* add a write to the transaction elements, so subsequent
+ reads see the zero data */
+ if (transaction_write(tdb, size, NULL, addition) != 0) {
+ return -1;
+ }
+
+ return 0;
+}
+
+/*
+ brlock during a transaction - ignore them
+*/
+int transaction_brlock(struct tdb_context *tdb, tdb_off_t offset,
+ int rw_type, int lck_type, int probe)
+{
+ return 0;
+}
+
+static const struct tdb_methods transaction_methods = {
+ .tdb_read = transaction_read,
+ .tdb_write = transaction_write,
+ .next_hash_chain = transaction_next_hash_chain,
+ .tdb_oob = transaction_oob,
+ .tdb_expand_file = transaction_expand_file,
+ .tdb_brlock = transaction_brlock
+};
+
+
+/*
+ start a tdb transaction. No token is returned, as only a single
+ transaction is allowed to be pending per tdb_context
+*/
+int tdb_transaction_start(struct tdb_context *tdb)
+{
+ /* some sanity checks */
+ if (tdb->read_only || (tdb->flags & TDB_INTERNAL)) {
+ TDB_LOG((tdb, 0, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
+ tdb->ecode = TDB_ERR_EINVAL;
+ return -1;
+ }
+
+ /* cope with nested tdb_transaction_start() calls */
+ if (tdb->transaction != NULL) {
+ tdb->transaction->nesting++;
+ TDB_LOG((tdb, 0, "tdb_transaction_start: nesting %d\n",
+ tdb->transaction->nesting));
+ return 0;
+ }
+
+ if (tdb->num_locks != 0) {
+ /* the caller must not have any locks when starting a
+ transaction as otherwise we'll be screwed by lack
+ of nested locks in posix */
+ TDB_LOG((tdb, 0, "tdb_transaction_start: cannot start a transaction with locks held\n"));
+ tdb->ecode = TDB_ERR_LOCK;
+ return -1;
+ }
+
+ tdb->transaction = calloc(sizeof(struct tdb_transaction), 1);
+ if (tdb->transaction == NULL) {
+ tdb->ecode = TDB_ERR_OOM;
+ return -1;
+ }
+
+ /* get the transaction write lock. This is a blocking lock. As
+ discussed with Volker, there are a number of ways we could
+ make this async, which we will probably do in the future */
+ if (tdb_brlock_len(tdb, TRANSACTION_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_start: failed to get transaction lock\n"));
+ tdb->ecode = TDB_ERR_LOCK;
+ SAFE_FREE(tdb->transaction);
+ return -1;
+ }
+
+ /* get a write lock from the freelist to the end of file. It
+ would be much better to make this a read lock as it would
+ increase parallelism, but it could lead to deadlocks on
+ commit when a write lock needs to be taken.
+
+ TODO: look at alternative locking strategies to allow this
+ to be a read lock
+ */
+ if (tdb_brlock_len(tdb, FREELIST_TOP, F_WRLCK, F_SETLKW, 0, 0) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_start: failed to get hash locks\n"));
+ tdb->ecode = TDB_ERR_LOCK;
+ goto fail;
+ }
+
+ /* setup a copy of the hash table heads so the hash scan in
+ traverse can be fast */
+ tdb->transaction->hash_heads = calloc(tdb->header.hash_size+1, sizeof(tdb_off_t));
+ if (tdb->transaction->hash_heads == NULL) {
+ tdb->ecode = TDB_ERR_OOM;
+ goto fail;
+ }
+ if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
+ TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
+ TDB_LOG((tdb, 0, "tdb_transaction_start: failed to read hash heads\n"));
+ tdb->ecode = TDB_ERR_IO;
+ goto fail;
+ }
+
+ /* make sure we know about any file expansions already done by
+ anyone else */
+ tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+ tdb->transaction->old_map_size = tdb->map_size;
+
+ /* finally hook the io methods, replacing them with
+ transaction specific methods */
+ tdb->transaction->io_methods = tdb->methods;
+ tdb->methods = &transaction_methods;
+
+ return 0;
+
+fail:
+ tdb_brlock_len(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 0);
+ tdb_brlock_len(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+ SAFE_FREE(tdb->transaction->hash_heads);
+ SAFE_FREE(tdb->transaction);
+ return -1;
+}
+
+
+/*
+ cancel the current transaction
+*/
+int tdb_transaction_cancel(struct tdb_context *tdb)
+{
+ if (tdb->transaction == NULL) {
+ TDB_LOG((tdb, 0, "tdb_transaction_cancel: no transaction\n"));
+ return -1;
+ }
+
+ if (tdb->transaction->nesting != 0) {
+ tdb->transaction->transaction_error = 1;
+ tdb->transaction->nesting--;
+ return 0;
+ }
+
+ tdb->map_size = tdb->transaction->old_map_size;
+
+ /* free all the transaction elements */
+ while (tdb->transaction->elements) {
+ struct tdb_transaction_el *el = tdb->transaction->elements;
+ tdb->transaction->elements = el->next;
+ free(el->data);
+ free(el);
+ }
+
+ /* remove any locks created during the transaction */
+ if (tdb->num_locks != 0) {
+ int h;
+ for (h=0;h<tdb->header.hash_size+1;h++) {
+ if (tdb->locked[h].count != 0) {
+ tdb_brlock_len(tdb,FREELIST_TOP+4*h,F_UNLCK,F_SETLKW, 0, 1);
+ tdb->locked[h].count = 0;
+ }
+ }
+ tdb->num_locks = 0;
+ }
+
+ /* restore the normal io methods */
+ tdb->methods = tdb->transaction->io_methods;
+
+ tdb_brlock_len(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW, 0, 0);
+ tdb_brlock_len(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+ SAFE_FREE(tdb->transaction->hash_heads);
+ SAFE_FREE(tdb->transaction);
+
+ return 0;
+}
+
+/*
+ sync to disk
+*/
+static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
+{
+ if (fsync(tdb->fd) != 0) {
+ tdb->ecode = TDB_ERR_IO;
+ TDB_LOG((tdb, 0, "tdb_transaction: fsync failed\n"));
+ return -1;
+ }
+#ifdef MS_SYNC
+ if (tdb->map_ptr) {
+ tdb_off_t moffset = offset & ~(tdb->page_size-1);
+ if (msync(moffset + (char *)tdb->map_ptr,
+ length + (offset - moffset), MS_SYNC) != 0) {
+ tdb->ecode = TDB_ERR_IO;
+ TDB_LOG((tdb, 0, "tdb_transaction: msync failed\n"));
+ return -1;
+ }
+ }
+#endif
+ return 0;
+}
+
+
+/*
+ work out how much space the linearised recovery data will consume
+*/
+static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
+{
+ struct tdb_transaction_el *el;
+ tdb_len_t recovery_size = 0;
+
+ recovery_size = sizeof(u32);
+ for (el=tdb->transaction->elements;el;el=el->next) {
+ if (el->offset >= tdb->transaction->old_map_size) {
+ continue;
+ }
+ recovery_size += 2*sizeof(tdb_off_t) + el->length;
+ }
+
+ return recovery_size;
+}
+
+/*
+ allocate the recovery area, or use an existing recovery area if it is
+ large enough
+*/
+static int tdb_recovery_allocate(struct tdb_context *tdb,
+ tdb_len_t *recovery_size,
+ tdb_off_t *recovery_offset,
+ tdb_len_t *recovery_max_size)
+{
+ struct list_struct rec;
+ const struct tdb_methods *methods = tdb->transaction->io_methods;
+ tdb_off_t recovery_head;
+
+ if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
+ TDB_LOG((tdb, 0, "tdb_recovery_allocate: failed to read recovery head\n"));
+ return -1;
+ }
+
+ rec.rec_len = 0;
+
+ if (recovery_head != 0 &&
+ methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
+ TDB_LOG((tdb, 0, "tdb_recovery_allocate: failed to read recovery record\n"));
+ return -1;
+ }
+
+ *recovery_size = tdb_recovery_size(tdb);
+
+ if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
+ /* it fits in the existing area */
+ *recovery_max_size = rec.rec_len;
+ *recovery_offset = recovery_head;
+ return 0;
+ }
+
+ /* we need to free up the old recovery area, then allocate a
+ new one at the end of the file. Note that we cannot use
+ tdb_allocate() to allocate the new one as that might return
+ us an area that is being currently used (as of the start of
+ the transaction) */
+ if (recovery_head != 0) {
+ if (tdb_free(tdb, recovery_head, &rec) == -1) {
+ TDB_LOG((tdb, 0, "tdb_recovery_allocate: failed to free previous recovery area\n"));
+ return -1;
+ }
+ }
+
+ /* the tdb_free() call might have increased the recovery size */
+ *recovery_size = tdb_recovery_size(tdb);
+
+ /* round up to a multiple of page size */
+ *recovery_max_size = TDB_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
+ *recovery_offset = tdb->map_size;
+ recovery_head = *recovery_offset;
+
+ if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
+ (tdb->map_size - tdb->transaction->old_map_size) +
+ sizeof(rec) + *recovery_max_size) == -1) {
+ TDB_LOG((tdb, 0, "tdb_recovery_allocate: failed to create recovery area\n"));
+ return -1;
+ }
+
+ /* remap the file (if using mmap) */
+ methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+
+ /* we have to reset the old map size so that we don't try to expand the file
+ again in the transaction commit, which would destroy the recovery area */
+ tdb->transaction->old_map_size = tdb->map_size;
+
+ /* write the recovery header offset and sync - we can sync without a race here
+ as the magic ptr in the recovery record has not been set */
+ CONVERT(recovery_head);
+ if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
+ &recovery_head, sizeof(tdb_off_t)) == -1) {
+ TDB_LOG((tdb, 0, "tdb_recovery_allocate: failed to write recovery head\n"));
+ return -1;
+ }
+
+ return 0;
+}
+
+
+/*
+ setup the recovery data that will be used on a crash during commit
+*/
+static int transaction_setup_recovery(struct tdb_context *tdb,
+ tdb_off_t *magic_offset)
+{
+ struct tdb_transaction_el *el;
+ tdb_len_t recovery_size;
+ unsigned char *data, *p;
+ const struct tdb_methods *methods = tdb->transaction->io_methods;
+ struct list_struct *rec;
+ tdb_off_t recovery_offset, recovery_max_size;
+ tdb_off_t old_map_size = tdb->transaction->old_map_size;
+ u32 magic;
+
+ /*
+ check that the recovery area has enough space
+ */
+ if (tdb_recovery_allocate(tdb, &recovery_size,
+ &recovery_offset, &recovery_max_size) == -1) {
+ return -1;
+ }
+
+ data = malloc(recovery_size + sizeof(*rec));
+ if (data == NULL) {
+ tdb->ecode = TDB_ERR_OOM;
+ return -1;
+ }
+
+ rec = (struct list_struct *)data;
+ memset(rec, 0, sizeof(*rec));
+
+ rec->magic = 0;
+ rec->data_len = recovery_size;
+ rec->rec_len = recovery_max_size;
+ rec->key_len = old_map_size;
+ CONVERT(rec);
+
+ /* build the recovery data into a single blob to allow us to do a single
+ large write, which should be more efficient */
+ p = data + sizeof(*rec);
+ for (el=tdb->transaction->elements;el;el=el->next) {
+ if (el->offset >= old_map_size) {
+ continue;
+ }
+ if (el->offset + el->length > tdb->transaction->old_map_size) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: transaction data over new region boundary\n"));
+ free(data);
+ tdb->ecode = TDB_ERR_CORRUPT;
+ return -1;
+ }
+ ((u32 *)p)[0] = el->offset;
+ ((u32 *)p)[1] = el->length;
+ if (DOCONV()) {
+ tdb_convert(p, 8);
+ }
+ /* the recovery area contains the old data, not the
+ new data, so we have to call the original tdb_read
+ method to get it */
+ if (methods->tdb_read(tdb, el->offset, p + 8, el->length, 0) != 0) {
+ free(data);
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+ p += 8 + el->length;
+ }
+
+ /* and the tailer */
+ *(u32 *)p = sizeof(*rec) + recovery_max_size;
+ CONVERT(p);
+
+ /* write the recovery data to the recovery area */
+ if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: failed to write recovery data\n"));
+ free(data);
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ /* as we don't have ordered writes, we have to sync the recovery
+ data before we update the magic to indicate that the recovery
+ data is present */
+ if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
+ free(data);
+ return -1;
+ }
+
+ free(data);
+
+ magic = TDB_RECOVERY_MAGIC;
+ CONVERT(magic);
+
+ *magic_offset = recovery_offset + offsetof(struct list_struct, magic);
+
+ if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: failed to write recovery magic\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ /* ensure the recovery magic marker is on disk */
+ if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
+ return -1;
+ }
+
+ return 0;
+}
+
+/*
+ commit the current transaction
+*/
+int tdb_transaction_commit(struct tdb_context *tdb)
+{
+ const struct tdb_methods *methods;
+ tdb_off_t magic_offset;
+ u32 zero = 0;
+
+ if (tdb->transaction == NULL) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: no transaction\n"));
+ return -1;
+ }
+
+ if (tdb->transaction->transaction_error) {
+ tdb->ecode = TDB_ERR_IO;
+ tdb_transaction_cancel(tdb);
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: transaction error pending\n"));
+ return -1;
+ }
+
+ if (tdb->transaction->nesting != 0) {
+ tdb->transaction->nesting--;
+ return 0;
+ }
+
+ /* check for a null transaction */
+ if (tdb->transaction->elements == NULL) {
+ tdb_transaction_cancel(tdb);
+ return 0;
+ }
+
+ methods = tdb->transaction->io_methods;
+
+ /* if there are any locks pending then the caller has not
+ nested their locks properly, so fail the transaction */
+ if (tdb->num_locks) {
+ tdb->ecode = TDB_ERR_LOCK;
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: locks pending on commit\n"));
+ tdb_transaction_cancel(tdb);
+ return -1;
+ }
+
+ /* get the global lock - this prevents new users attaching to the database
+ during the commit */
+ if (tdb_brlock_len(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: failed to get global lock\n"));
+ tdb->ecode = TDB_ERR_LOCK;
+ tdb_transaction_cancel(tdb);
+ return -1;
+ }
+
+ if (!(tdb->flags & TDB_NOSYNC)) {
+ /* write the recovery data to the end of the file */
+ if (transaction_setup_recovery(tdb, &magic_offset) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: failed to setup recovery data\n"));
+ tdb_brlock_len(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+ tdb_transaction_cancel(tdb);
+ return -1;
+ }
+ }
+
+ /* expand the file to the new size if needed */
+ if (tdb->map_size != tdb->transaction->old_map_size) {
+ if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
+ tdb->map_size -
+ tdb->transaction->old_map_size) == -1) {
+ tdb->ecode = TDB_ERR_IO;
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: expansion failed\n"));
+ tdb_brlock_len(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+ tdb_transaction_cancel(tdb);
+ return -1;
+ }
+ tdb->map_size = tdb->transaction->old_map_size;
+ methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+ }
+
+ /* perform all the writes */
+ while (tdb->transaction->elements) {
+ struct tdb_transaction_el *el = tdb->transaction->elements;
+
+ if (methods->tdb_write(tdb, el->offset, el->data, el->length) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: write failed during commit\n"));
+
+ /* we've overwritten part of the data and
+ possibly expanded the file, so we need to
+ run the crash recovery code */
+ tdb->methods = methods;
+ tdb_transaction_recover(tdb);
+
+ tdb_transaction_cancel(tdb);
+ tdb_brlock_len(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: write failed\n"));
+ return -1;
+ }
+ tdb->transaction->elements = el->next;
+ free(el->data);
+ free(el);
+ }
+
+ if (!(tdb->flags & TDB_NOSYNC)) {
+ /* ensure the new data is on disk */
+ if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
+ return -1;
+ }
+
+ /* remove the recovery marker */
+ if (methods->tdb_write(tdb, magic_offset, &zero, 4) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_commit: failed to remove recovery magic\n"));
+ return -1;
+ }
+
+ /* ensure the recovery marker has been removed on disk */
+ if (transaction_sync(tdb, magic_offset, 4) == -1) {
+ return -1;
+ }
+ }
+
+ tdb_brlock_len(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+
+ /* use a transaction cancel to free memory and remove the
+ transaction locks */
+ tdb_transaction_cancel(tdb);
+ return 0;
+}
+
+
+/*
+ recover from an aborted transaction. Must be called with exclusive
+ database write access already established (including the global
+ lock to prevent new processes attaching)
+*/
+int tdb_transaction_recover(struct tdb_context *tdb)
+{
+ tdb_off_t recovery_head, recovery_eof;
+ unsigned char *data, *p;
+ u32 zero = 0;
+ struct list_struct rec;
+
+ /* find the recovery area */
+ if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to read recovery head\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ if (recovery_head == 0) {
+ /* we have never allocated a recovery record */
+ return 0;
+ }
+
+ /* read the recovery record */
+ if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
+ sizeof(rec), DOCONV()) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to read recovery record\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ if (rec.magic != TDB_RECOVERY_MAGIC) {
+ /* there is no valid recovery data */
+ return 0;
+ }
+
+ if (tdb->read_only) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: attempt to recover read only database\n"));
+ tdb->ecode = TDB_ERR_CORRUPT;
+ return -1;
+ }
+
+ recovery_eof = rec.key_len;
+
+ data = malloc(rec.data_len);
+ if (data == NULL) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to allocate recovery data\n"));
+ tdb->ecode = TDB_ERR_OOM;
+ return -1;
+ }
+
+ /* read the full recovery data */
+ if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
+ rec.data_len, 0) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to read recovery data\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ /* recover the file data */
+ p = data;
+ while (p+8 < data + rec.data_len) {
+ u32 ofs, len;
+ if (DOCONV()) {
+ tdb_convert(p, 8);
+ }
+ ofs = ((u32 *)p)[0];
+ len = ((u32 *)p)[1];
+
+ if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
+ free(data);
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+ p += 8 + len;
+ }
+
+ free(data);
+
+ if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to sync recovery\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ /* if the recovery area is after the recovered eof then remove it */
+ if (recovery_eof <= recovery_head) {
+ if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to remove recovery head\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+ }
+
+ /* remove the recovery magic */
+ if (tdb_ofs_write(tdb, recovery_head + offsetof(struct list_struct, magic),
+ &zero) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to remove recovery magic\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ /* reduce the file size to the old size */
+ tdb_munmap(tdb);
+ if (ftruncate(tdb->fd, recovery_eof) != 0) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to reduce to recovery size\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+ tdb->map_size = recovery_eof;
+ tdb_mmap(tdb);
+
+ if (transaction_sync(tdb, 0, recovery_eof) == -1) {
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: failed to sync2 recovery\n"));
+ tdb->ecode = TDB_ERR_IO;
+ return -1;
+ }
+
+ TDB_LOG((tdb, 0, "tdb_transaction_recover: recovered %d byte database\n",
+ recovery_eof));
+
+ /* all done */
+ return 0;
+}
generated by cgit (git 2.34.1) at 2024-11-13 01:28:04 +0000