Excessive stat syscalls on linux

[the8472]

The directory traversal performs a .metadata() on each entry to check whether it is a directory, which results in a syscall. This is extremely wasteful since DirEntry::file_type can grab the file type directly from the readdir results which are obtained in batches via getdents syscall, i.e. only 1 syscall every N directory entries.

An additional problem is that there are multiple metadata() calls. They are not cached on the file descriptor, so each call results in an additional syscall.

[NilsIrl]

Maybe this could also be fixed by improving the standard library? As it stands, I don't think there's anyway to access the results of readdir in rust (using the standard library). So I think this is more of a problem to do with the standard library.

[the8472]

I don't think there's anyway to access the results of readdir in rust (using the standard library).

There is, I explicitly mentioned it in my initial comment

This is extremely wasteful since DirEntry::file_type can grab the file type directly from the readdir results