tdb: TDB_INCOMPATIBLE_HASH, to allow safe changing of default hash.

[obnox/samba-ctdb.git] / lib / tdb / common / open.c

diff --git a/lib/tdb/common/open.c b/lib/tdb/common/open.c
index 0633bc1f5f6d8cf0a21b47adb4f6f6649519b131..27fe8fceb0852c67a6a5d3d3f8f0f54001029165 100644 (file)
--- a/lib/tdb/common/open.c
+++ b/lib/tdb/common/open.c
@@ -69,6 +69,11 @@ static int tdb_new_database(struct tdb_context *tdb, int hash_size)
 
        tdb_header_hash(tdb, &newdb->magic1_hash, &newdb->magic2_hash);
 
+       /* Make sure older tdbs (which don't check the magic hash fields)
+        * will refuse to open this TDB. */
+       if (tdb->flags & TDB_INCOMPATIBLE_HASH)
+               newdb->rwlocks = TDB_HASH_RWLOCK_MAGIC;
+
        if (tdb->flags & TDB_INTERNAL) {
                tdb->map_size = size;
                tdb->map_ptr = (char *)newdb;
@@ -163,7 +168,10 @@ static bool check_header_hash(struct tdb_context *tdb,
                return false;
 
        /* Otherwise, try the other inbuilt hash. */
-       tdb->hash_fn = tdb_jenkins_hash;
+       if (tdb->hash_fn == tdb_old_hash)
+               tdb->hash_fn = tdb_jenkins_hash;
+       else
+               tdb->hash_fn = tdb_old_hash;
        return check_header_hash(tdb, false, m1, m2);
 }
 
@@ -203,7 +211,12 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
                tdb->hash_fn = hash_fn;
                hash_alg = "the user defined";
        } else {
-               tdb->hash_fn = tdb_old_hash;
+               /* This controls what we use when creating a tdb. */
+               if (tdb->flags & TDB_INCOMPATIBLE_HASH) {
+                       tdb->hash_fn = tdb_jenkins_hash;
+               } else {
+                       tdb->hash_fn = tdb_old_hash;
+               }
                hash_alg = "either default";
        }
 
@@ -299,13 +312,15 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
        if (fstat(tdb->fd, &st) == -1)
                goto fail;
 
-       if (tdb->header.rwlocks != 0) {
+       if (tdb->header.rwlocks != 0 &&
+           tdb->header.rwlocks != TDB_HASH_RWLOCK_MAGIC) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_open_ex: spinlocks no longer supported\n"));
                goto fail;
        }
 
        if ((tdb->header.magic1_hash == 0) && (tdb->header.magic2_hash == 0)) {
                /* older TDB without magic hash references */
+               tdb->hash_fn = tdb_old_hash;
        } else if (!check_header_hash(tdb, !hash_fn, &magic1, &magic2)) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: "
                         "%s was not created with %s hash function we are using\n"