Feature or enhancement

Proposal:

Currently posixpath.ismount uses realpath(join(path, '..')) to get the parent of the mount. This is absolutely overkill and should only be used when join(path, '..') isn't sufficient.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

• gh-117349: Micro-optimize a few os.path functions #117350

Linked PRs

• gh-117394: Reduce syscalls for posixpath.ismount #117395
• gh-117394: Speed up os.path.ismount() on Posix #117447