Defining PATH_MAX for a filesystem?

Question

I\'m presently writing a filesystem. The statvfs (and even the statfs) structs contain a field specifying the maximum length of a name in that path. As PATH_M

Answer 1

On Linux, glibc's implementation of pathconf returns a compile-time constant value of PATH_MAX so there is no runtime magic FUSE or anyone else can perform to adjust it. (See sysdeps/unix/sysv/linux/pathconf.c which falls through to sysdeps/posix/pathconf.c.) The answer to your question "How do I specify my filesystem's PATH_MAX?" is "You can't. glibc doesn't let you and FUSE is just the messenger."

The end result is a sticky situation. Here's a blog post that discusses the code that does and does not care about PATH_MAX. Software that relies on paths no longer than PATH_MAX was broken long ago by other filesystems so it's safe for you to ignore PATH_MAX.

On MacOS X (and probably other BSDs): The implementation of pathconf is entirely in the kernel and can be swapped out per filesystem. OSXFUSE includes a NOOP version of pathconf which should return the usual compile-time constants. However, in my tests it seems to be catching another NOOP function along the way which returns an ENXIO and I can't get pathconf to work.

Bonus: for NAME_MAX, implement statfs and set f_namemax.