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authorAndrew Tridgell <tridge@samba.org>2006-03-30 04:52:39 +0000
committerGerald (Jerry) Carter <jerry@samba.org>2007-10-10 13:59:20 -0500
commit3387746c4517d6766146080980ac467b72b62316 (patch)
treebe82b9daf54552306123f38d88330460825dfcf4 /source4/lib/tdb/common
parent86971ff3b930a93de55aae00fe66f3d1d10dbcb4 (diff)
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r14799: added a tdb_get_seqnum() call, and the TDB_SEQNUM flag. This allows
for an extremely lightweight test to see if a tdb has possibly changed. (This used to be commit f325ba605ccceca63712c0f2c98961e35e437b3d)
Diffstat (limited to 'source4/lib/tdb/common')
-rw-r--r--source4/lib/tdb/common/tdb.c54
-rw-r--r--source4/lib/tdb/common/tdb_private.h4
-rw-r--r--source4/lib/tdb/common/transaction.c6
3 files changed, 63 insertions, 1 deletions
diff --git a/source4/lib/tdb/common/tdb.c b/source4/lib/tdb/common/tdb.c
index 4b0d4a31c5..b0411601eb 100644
--- a/source4/lib/tdb/common/tdb.c
+++ b/source4/lib/tdb/common/tdb.c
@@ -30,6 +30,33 @@
TDB_DATA tdb_null;
+/*
+ increment the tdb sequence number if the tdb has been opened using
+ the TDB_SEQNUM flag
+*/
+static void tdb_increment_seqnum(struct tdb_context *tdb)
+{
+ tdb_off_t seqnum=0;
+
+ if (!(tdb->flags & TDB_SEQNUM)) {
+ return;
+ }
+
+ if (tdb_brlock(tdb, TDB_SEQNUM_OFS, F_WRLCK, F_SETLKW, 1) != 0) {
+ return;
+ }
+
+ /* we ignore errors from this, as we have no sane way of
+ dealing with them.
+ */
+ tdb_ofs_read(tdb, TDB_SEQNUM_OFS, &seqnum);
+ seqnum++;
+ tdb_ofs_write(tdb, TDB_SEQNUM_OFS, &seqnum);
+
+ tdb_brlock(tdb, TDB_SEQNUM_OFS, F_UNLCK, F_SETLKW, 1);
+}
+
+
/* Returns 0 on fail. On success, return offset of record, and fills
in rec */
static tdb_off_t tdb_find(struct tdb_context *tdb, TDB_DATA key, u32 hash,
@@ -203,6 +230,11 @@ static int tdb_delete_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash)
if (!(rec_ptr = tdb_find_lock_hash(tdb, key, hash, F_WRLCK, &rec)))
return -1;
ret = tdb_do_delete(tdb, rec_ptr, &rec);
+
+ if (ret == 0) {
+ tdb_increment_seqnum(tdb);
+ }
+
if (tdb_unlock(tdb, BUCKET(rec.full_hash), F_WRLCK) != 0)
TDB_LOG((tdb, 0, "tdb_delete: WARNING tdb_unlock failed!\n"));
return ret;
@@ -295,6 +327,9 @@ int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
/* Need to tdb_unallocate() here */
goto fail;
}
+
+ tdb_increment_seqnum(tdb);
+
out:
SAFE_FREE(p);
tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
@@ -369,3 +404,22 @@ tdb_log_func tdb_log_fn(struct tdb_context *tdb)
{
return tdb->log_fn;
}
+
+
+/*
+ get the tdb sequence number. Only makes sense if the writers opened
+ with TDB_SEQNUM set. Note that this sequence number will wrap quite
+ quickly, so it should only be used for a 'has something changed'
+ test, not for code that relies on the count of the number of changes
+ made. If you want a counter then use a tdb record.
+
+ The aim of this sequence number is to allow for a very lightweight
+ test of a possible tdb change.
+*/
+int tdb_get_seqnum(struct tdb_context *tdb)
+{
+ tdb_off_t seqnum=0;
+
+ tdb_ofs_read(tdb, TDB_SEQNUM_OFS, &seqnum);
+ return seqnum;
+}
diff --git a/source4/lib/tdb/common/tdb_private.h b/source4/lib/tdb/common/tdb_private.h
index d7193b2b67..d01a88695d 100644
--- a/source4/lib/tdb/common/tdb_private.h
+++ b/source4/lib/tdb/common/tdb_private.h
@@ -94,6 +94,7 @@ typedef u32 tdb_off_t;
#define TDB_HASHTABLE_SIZE(tdb) ((tdb->header.hash_size+1)*sizeof(tdb_off_t))
#define TDB_DATA_START(hash_size) TDB_HASH_TOP(hash_size-1)
#define TDB_RECOVERY_HEAD offsetof(struct tdb_header, recovery_start)
+#define TDB_SEQNUM_OFS offsetof(struct tdb_header, sequence_number)
#define TDB_PAD_BYTE 0x42
#define TDB_PAD_U32 0x42424242
@@ -155,7 +156,8 @@ struct tdb_header {
u32 hash_size; /* number of hash entries */
tdb_off_t rwlocks; /* obsolete - kept to detect old formats */
tdb_off_t recovery_start; /* offset of transaction recovery region */
- tdb_off_t reserved[30];
+ tdb_off_t sequence_number; /* used when TDB_SEQNUM is set */
+ tdb_off_t reserved[29];
};
struct tdb_lock_type {
diff --git a/source4/lib/tdb/common/transaction.c b/source4/lib/tdb/common/transaction.c
index ace4aa51a6..6960a02ad8 100644
--- a/source4/lib/tdb/common/transaction.c
+++ b/source4/lib/tdb/common/transaction.c
@@ -892,6 +892,12 @@ int tdb_transaction_commit(struct tdb_context *tdb)
tdb_brlock_len(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
+ /*
+ TODO: maybe write to some dummy hdr field, or write to magic
+ offset without mmap, before the last sync, instead of the
+ utime() call
+ */
+
/* on some systems (like Linux 2.6.x) changes via mmap/msync
don't change the mtime of the file, this means the file may
not be backed up (as tdb rounding to block sizes means that