[PATCH 0/1] turn mm->exe_file into mm->exe_path

[Oleg Nesterov <oleg@redhat.com>]

I think the patch is simple and self-explanatory, it simply
does s/mm->exe_file/mm->exe_path/.

Why do we need mm->exe_file? IIUC, there are 2 reasons:

	1. we do not want O(n) proc/pid/exe looking for the 1st
	   VM_EXECUTABLE vma.

	2. we do not want to rely on vma->vm_file->f_path,
	   bprm->file->f_op->mmap can change ->vm_file.

Unless there was another subtle reason, "struct path *exe_path"
can equally work but it looks more clear.



And can't we also remove added_exe_file_vma/removed_exe_file_vma?
Why do we need mm->num_exe_file_vmas? Afaics it is only needed to
"free" mm->exe_file if the application unmaps all these vmas. Say,
to allow to unmount fs.

Can't we simply add PR_CLEAR_MM_EXE_PATH instead? Of course it is
not enough if ->vm_file still has a reference. But c/r people want
PR_SET_MM_EXE_FILE anyway, see http://marc.info/?t=133052865500016
So perhaps we can add PR_SET_MM_EXE_PATH which accepts NULL as well
and kill this counter?

Oleg.