This is iget without the read_inode portion of get_new_inode_fast.
iget_locked uses ifind_fast to search for the inode specified by ino in the inode cache and if present it is returned with an increased reference count. This is for file systems where the inode number is sufficient for unique identification of an inode.
If the inode is not in cache, get_new_inode_fast is called to allocate a new inode and this is returned locked, hashed, and with the I_NEW flag set. The file system gets to fill it in before unlocking it via unlock_new_inode.