linux-kernel - Re: + mm-remove-struct-mm_struct-exe_file-et-al.patch added to -mm tree

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Message-ID: <20090331144051.GA3951@redhat.com>
Date:	Tue, 31 Mar 2009 16:40:51 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, adobriyan@...il.com,
	dhowells@...hat.com, ebiederm@...ssion.com, hch@....de,
	matthltc@...ibm.com
Subject: Re: + mm-remove-struct-mm_struct-exe_file-et-al.patch added to -mm
	tree

s/mm-commits/lkml/

On 03/30, Andrew Morton wrote:
>
> From: Alexey Dobriyan <adobriyan@...il.com>
>
> Commit 925d1c401fa6cfd0df5d2e37da8981494ccdec07 ("procfs task exe
> symlink").  introduced struct mm_struct::exe_file and struct
> mm_struct::num_exe_file_vmas.
>
> The rationale is weak: unifying MMU and no-MMU version of /proc/*/exe
> code.  For this a) struct mm_struct becomes bigger, b) mmap/munmap/exit
> become slower, c) patch adds more code than removes in fact.
>
> ->exe_file maybe well defined, but doesn't make sense always.  After
> original executable is unmapped, /proc/*/exe will still report it and,
> more importantly, pin corresponding struct file.

I never liked the change which introduced mm->exe_file, so I vote for
this patch.

But, as a advocatus diaboli... There was anotrher reason for ->exe_file,
iirc.

bprm->file->f_op->mmap() can change vma->vm_file, this means proc_exe_link()
can report the "wrong" path. The original file is not pinned in this case.

Matt?

Oleg.

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