Determine a file's path(s) relative to a directory, including symlinks

I have a directory with thousands of descendants. Given a file path (which is guaranteed to exist), I want to know where that file can be found inside that directory -- including via symlinks. (The motivation is that a file has changed and I need to know what parts of the directory tree are affected.)

For example, given:

• The directory path is /base.
• The real file path is /elsewhere/myfile.
• /base is a symlink to /realbase
• /realbase/foo is a symlink to /elsewhere.
• /realbase/bar/baz is a symlink to /elsewhere/myfile.

I want to find the paths /base/foo/myfile and /base/bar/baz.

I could do this by recursively checking every symlink in /base, but this would be very slow. I'm hoping that there's a more graceful solution.

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