MDEV-10508 Mariadb crash on out of disk space during dump import

update info->write_end and info->write_pos together, with no
"return on error" in between, otherwise write_end might end up being
smaller than write_pos

mysql-test/r/slowlog_enospace-10508.result

+call mtr.add_suppression('Error writing file.*errno: 28 ');
+create table t1 (a int, b int) engine=memory;
+insert t1 select seq, seq+1 from seq_1_to_1000;
+set global general_log=0;
+set global log_queries_not_using_indexes=1;
+set debug_dbug='+d,simulate_file_write_error';
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+select * from t1 where a>10;
+set debug_dbug='';
+set global general_log=1;
+set global log_queries_not_using_indexes=default;
+drop table t1;

mysql-test/t/slowlog_enospace-10508.test

+#
+# MDEV-10508 Mariadb crash on out of disk space during dump import
+#
+--source include/have_sequence.inc
+--source include/have_debug.inc
+
+call mtr.add_suppression('Error writing file.*errno: 28 ');
+create table t1 (a int, b int) engine=memory;
+insert t1 select seq, seq+1 from seq_1_to_1000;
+set global general_log=0;
+set global log_queries_not_using_indexes=1;
+set debug_dbug='+d,simulate_file_write_error';
+--disable_result_log
+--let $run= 50
+while ($run)
+{
+    select * from t1 where a>10;
+    dec $run;
+}
+--enable_result_log
+set debug_dbug='';
+set global general_log=1;
+set global log_queries_not_using_indexes=default;
+drop table t1;

mysys/mf_iocache.c

@@ -1825,8 +1825,6 @@ int my_b_flush_io_cache(IO_CACHE *info, int need_append_buffer_lock)
 
     if ((length=(size_t) (info->write_pos - info->write_buffer)))
     {
-      info->write_end= (info->write_buffer + info->buffer_length -
-                        ((info->pos_in_file + length) & (IO_SIZE - 1)));
       if (append_cache)
       {
 
@@ -1848,6 +1846,8 @@ int my_b_flush_io_cache(IO_CACHE *info, int need_append_buffer_lock)
 
         set_if_bigger(info->end_of_file, info->pos_in_file);
       }
+      info->write_end= (info->write_buffer + info->buffer_length -
+                        ((info->pos_in_file + length) & (IO_SIZE - 1)));
       info->write_pos= info->write_buffer;
       ++info->disk_writes;
       UNLOCK_APPEND_BUFFER;