Finding goal in ext4 file system

Question

The file extents.c (fs/ext4/extents.c) in linux kernel 4.7.2 deals with file allocation methods.

ar.goal is calculated by a function ext4_ext_find_goal

ar.goal = ext4_ext_find_goal(inode, path, map->m_lblk);

Can anyone please explain how this function works ?

Answer 1

ext4_ext_find_goal() is called when we need to allocate new block.

In here , this function is called as you said.

ar.goal = ext4_ext_find_goal(inode, path, map->m_lblk);

In this context, path is not NULL. So, ext4_ext_find_goal() will find block number of that path , and return this block number.