Re: [PATCH] remove_arg_zero() rewrite

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

On Wed, 2007-03-07 at 14:41 -0800, Andrew Morton wrote:
> On Wed, 07 Mar 2007 23:09:57 +0100
> Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> 
> > On Wed, 2007-02-21 at 15:41 -0800, Andrew Morton wrote:
> > 
> > > I mean.... what the hell?
> > > 
> > > As you appear to have managed to work out what the sorry thing is trying to
> > > do, would you have time to simply rip it out and completely rewrite it,
> > > including a nice comment telling the world what this function's function is?
> > > 
> > > Because what we have there is beyond repairing.
> > 
> > Something like so?
> > Boots uml seemingly without errors.
> > 
> > ---
> > Rewrite remove_arg_zero() to be more parseable by untwisted minds.
> > 
> 
> Sorry, Nick already had a go at this:

Darn, must've fell off of lkml... or I missed it catching up my 4000+
email backlog.

> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc2/2.6.21-rc2-mm2/broken-out/exec-fix-remove_arg_zero.patch
> 
> But your patch has a nice comment and has to be better ;)

Ah, but now I finally see the initial problem.

My patch is bug compatible and doesn't free the head page when that
becomes unused.

This should do on top:

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---

Index: linux-2.6/fs/exec.c
===================================================================
--- linux-2.6.orig/fs/exec.c	2007-03-07 23:51:31.000000000 +0100
+++ linux-2.6/fs/exec.c	2007-03-07 23:50:41.000000000 +0100
@@ -1011,6 +1011,11 @@ void remove_arg_zero(struct linux_binprm
 			;
 
 		kunmap_atomic(kaddr, KM_USER0);
+
+		if (offset == PAGE_SIZE) {
+			__free_page(page);
+			bprm->page[(bprm->p >> PAGE_SHIFT) - 1] = NULL;
+		}
 	} while (offset == PAGE_SIZE);
 
 	bprm->p++;