[PATCH 3/3] powerpc/oprofile: reduce mmap_sem hold for exe_file

In the future mm->exe_file will be done without mmap_sem serialization, thus isolate and reorganize the related code to make the transition easier. Good users will, make use of the more standard get_mm_exe_file(), requiring only holding the mmap_sem to read the value, and relying on reference

[PATCH 3/3] powerpc/oprofile: reduce mmap_sem hold for exe_file

In the future mm-exe_file will be done without mmap_sem serialization, thus isolate and reorganize the related code to make the transition easier. Good users will, make use of the more standard get_mm_exe_file(), requiring only holding the mmap_sem to read the value, and relying on reference