Theoretically, I don't see much problem by changing the checks way you have done in patch, but it becomes different than what we have in destroy_tablespace_directories() and it is slightly changing the way check was originally done in create_tablespace_directories(), basically original check will try unlink if lstat returns non-zero return code. If you want to proceed with the changed checks as in v3, then may be we can modify comments on top of function remove_tablespace_symlink() which indicates that it works like destroy_tablespace_directories().
The difference is that here we're getting the list from a base backup and it seems to me the risk of having a file we don't really want to unlink is significantly greater.
Okay, I think I can understand why you want to be cautious for
having a different check for this path, but in that case there is a
chance that recovery might fail when it will try to create a symlink
for that file. Shouldn't we then try to call this new function only
when we are trying to restore from tablespace_map file and also
is there a need of ifdef S_ISLINK in remove_tablespace_link?
