From: Matt Helsley <matthltc@us.ibm.com>
To: Matt Helsley <matthltc@us.ibm.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
xemul@parallels.com, containers@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, dave@linux.vnet.ibm.com,
mingo@elte.hu, torvalds@linux-foundation.org,
linux-fsdevel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 1/9] exec_path 1/9: introduce ->exec_path and switch /proc/*/exe
Date: Thu, 4 Jun 2009 01:10:46 -0700 [thread overview]
Message-ID: <20090604081046.GV9285@us.ibm.com> (raw)
In-Reply-To: <20090604075532.GU9285@us.ibm.com>
On Thu, Jun 04, 2009 at 12:55:32AM -0700, Matt Helsley wrote:
> On Thu, Jun 04, 2009 at 03:04:22AM +0400, Alexey Dobriyan wrote:
> > On Sun, May 31, 2009 at 03:19:53PM -0700, Andrew Morton wrote:
> > > On Mon, 1 Jun 2009 01:54:27 +0400 Alexey Dobriyan <adobriyan@gmail.com> wrote:
> > >
> > > > And BTW, there is something unnatural when executable path is attached
> > > > to mm_struct(!) not task_struct,
> > >
> > > mm_struct is the central object for a heavyweight process. All threads
> > > within that process share the same executable path (don't they?) so
> > > attaching the executable path to the mm seems OK to me.
> >
> > OK, let's try this:
> >
> >
> > [PATCH 1/9] exec_path 1/9: introduce ->exec_path and switch /proc/*/exe
> >
> > ->exec_path marks executable which is associated with running task.
> > Binfmt loader decides which executable is such and can, in theory,
> > assign anything. Unlike current status quo when first VM_EXECUTABLE mapping is
> > sort of marks running executable.
> >
> > If executable unmaps its all VM_EXECUTABLE mappings, /proc/*/exe ceases
> > to exists, ick! And userpsace can't even use MAP_EXECUTABLE.
>
> Suprising but intentional and unavoidable. More below..
>
> >
> > Tasks which aren't created by running clone(2) and execve(2)
> > (read: kernel threads) get empty ->exec_path and
> >
> > ->exec_path is copied on clone(2) and put at do_exit() time.
>
> Doesn't this pin the vfs mount of the executable for the lifetime of
> the task?
>
> That was one of Al Viro's objections to early revisions of the exe_file
> patches. It's the reason the exe_file patches kept track of the number of
> VM_EXECUTABLE mappings with num_exe_file_vmas.
>
> I've cc'd Al so he can confirm/deny my recollection of this. Basically
> some programs need to be able to umount the filesystem that back their
> executables. Being able to unmap these regions was effectively a
> userspace API for unpinning these mounts. I needed to preserve that API,
> hence the VMA ugliness of exe_file that you object to with the exe_file
> patches.
>
> I think patches 2-7 look great and could be adapted to use exe_file instead
> of ->exec_path.
Well, except 5 and 6.
Alternately, I think you could use the same VMA code with ->exec_path to avoid
pinning the vfs mount. However, then it would probably be best to move
it into the mm just like exe_file...
>
> Cheers,
> -Matt Helsley
next prev parent reply other threads:[~2009-06-04 8:10 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20090526113618.GJ28083@us.ibm.com>
[not found] ` <20090526162415.fb9cefef.akpm@linux-foundation.org>
[not found] ` <20090531215427.GA29534@x200.localdomain>
[not found] ` <20090531151953.8f8b14b5.akpm@linux-foundation.org>
[not found] ` <20090531151953.8f8b14b5.akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
2009-06-03 23:04 ` [PATCH 1/9] exec_path 1/9: introduce ->exec_path and switch /proc/*/exe Alexey Dobriyan
2009-06-03 23:05 ` [PATCH 2/9] exec_path 2/9: switch audit to ->exec_path Alexey Dobriyan
[not found] ` <20090603230422.GB853-2ev+ksY9ol182hYKe6nXyg@public.gmane.org>
2009-06-03 23:05 ` [PATCH 3/9] exec_path 3/9: switch TOMOYO " Alexey Dobriyan
2009-06-03 23:06 ` [PATCH 4/9] exec_path 4/9: switch oprofile " Alexey Dobriyan
2009-06-03 23:06 ` [PATCH 6/9] exec_path 6/9: add struct spu::tsk Alexey Dobriyan
2009-06-03 23:06 ` [PATCH 5/9] exec_path 5/9: make struct spu_context::owner task_struct Alexey Dobriyan
2009-06-03 23:07 ` [PATCH 7/9] exec_path 7/9: switch cell SPU thing to ->exec_path Alexey Dobriyan
2009-06-03 23:07 ` [PATCH 8/9] exec_path 8/9: remove ->exe_file et al Alexey Dobriyan
2009-06-03 23:08 ` [PATCH 9/9] exec_path 9/9: remove VM_EXECUTABLE Alexey Dobriyan
2009-06-04 7:24 ` Matt Helsley
2009-06-03 23:36 ` [PATCH 1/9] exec_path 1/9: introduce ->exec_path and switch /proc/*/exe Linus Torvalds
2009-06-04 7:55 ` Matt Helsley
2009-06-04 8:10 ` Matt Helsley [this message]
2009-06-04 15:07 ` Linus Torvalds
2009-06-04 21:30 ` Matt Helsley
2009-06-04 22:42 ` Alexey Dobriyan
2009-06-05 3:49 ` Matt Helsley
2009-06-05 10:45 ` Christoph Hellwig
2009-06-05 15:10 ` Linus Torvalds
2009-06-05 15:41 ` Alexey Dobriyan
2009-06-05 15:49 ` Linus Torvalds
2009-06-05 16:09 ` Alexey Dobriyan
[not found] ` <20090605160943.GA5262-2ev+ksY9ol182hYKe6nXyg@public.gmane.org>
2009-06-05 16:48 ` Linus Torvalds
2009-06-05 17:46 ` Alexey Dobriyan
2009-06-06 7:22 ` Al Viro
2009-06-15 22:10 ` Alexey Dobriyan
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