Add mdb_env_set_pagesize()

libraries/liblmdb/lmdb.h

@@ -908,6 +908,16 @@ int  mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *fd);
 	 */
 int  mdb_env_set_mapsize(MDB_env *env, mdb_size_t size);
 
+
+	/** @brief Set the size of DB pages in bytes.
+	 *
+	 * The size defaults to the OS page size. Smaller or larger values may be
+	 * desired depending on the size of keys and values being used. Also, an
+	 * explicit size may need to be set when using filesystems like ZFS which
+	 * don't use the OS page size.
+	 */
+int  mdb_env_set_pagesize(MDB_env *env, int size);
+
 	/** @brief Set the maximum number of threads/reader slots for the environment.
 	 *
 	 * This defines the number of slots in the lock table that is used to track readers in the

libraries/liblmdb/mdb.c

@@ -4439,6 +4439,8 @@ mdb_env_read_header(MDB_env *env, int prev, MDB_meta *meta)
 		env->me_mapsize &= ~(VM_ALIGN-1);
 		env->me_psize = env->me_os_psize;
 		rc = mdb_env_map(env, NULL);
+		if (rc)
+			return rc;
 		p = (MDB_page *)env->me_map;
 		for (i=0; i<NUM_METAS; i++) {
 			if (!F_ISSET(p->mp_flags, P_META))
@@ -11270,6 +11272,19 @@ mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *arg)
 	return MDB_SUCCESS;
 }
 
+int ESECT
+mdb_env_set_pagesize(MDB_env *env, int size)
+{
+	if (!env || env->me_map)
+		return EINVAL;
+	if (size > MAX_PAGESIZE || size < 256)
+		return EINVAL;
+	if (size & (size-1))
+		return EINVAL;
+	env->me_os_psize = size;
+	return MDB_SUCCESS;
+}
+
 /** Common code for #mdb_stat() and #mdb_env_stat().
  * @param[in] env the environment to operate in.
  * @param[in] db the #MDB_db record containing the stats to return.

libraries/liblmdb/mtest.c

@@ -47,6 +47,7 @@ int main(int argc,char * argv[])
 		E(mdb_env_create(&env));
 		E(mdb_env_set_maxreaders(env, 1));
 		E(mdb_env_set_mapsize(env, 10485760));
+		E(mdb_env_set_pagesize(env, 1024));
 		E(mdb_env_open(env, "./testdb", MDB_FIXEDMAP /*|MDB_NOSYNC*/, 0664));
 
 		E(mdb_txn_begin(env, NULL, 0, &txn));