linux-kernel - [RFC][PATCH] don't show pgoff of vma if vma is pure ANON (was Re: mmotm 2009-01-12-16-53 uploaded)

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Message-Id: <20090114162245.923c4caf.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Wed, 14 Jan 2009 16:22:45 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Mike Waychison <mikew@...gle.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, yinghan@...gle.com,
	hugh@...itas.com
Subject: [RFC][PATCH] don't show pgoff of vma if vma is pure ANON (was Re:
 mmotm 2009-01-12-16-53 uploaded)

On Tue, 13 Jan 2009 09:05:28 -0800
Mike Waychison <mikew@...gle.com> wrote:


> > ===================================================================
> > --- mmotm-2.6.29-Jan12.orig/fs/exec.c
> > +++ mmotm-2.6.29-Jan12/fs/exec.c
> > @@ -509,7 +509,7 @@ static int shift_arg_pages(struct vm_are
> >  	unsigned long length = old_end - old_start;
> >  	unsigned long new_start = old_start - shift;
> >  	unsigned long new_end = old_end - shift;
> > -	unsigned long new_pgoff = new_start >> PAGE_SHIFT;
> > +	unsigned long new_pgoff = vma->vm_pgoff;
> >  	struct mmu_gather *tlb;
> >  
> >  	BUG_ON(new_start > new_end);
> > 
> 
> This patch is just reverting the behaviour back to having a 64bit pgoff. 
>   Best just reverting the patch for the time being.
> 
Hmm, is this brutal ?

==
Recently, it's argued that what proc/pid/maps shows is ugly when a
32bit binary runs on 64bit host.

/proc/pid/maps outputs vma's pgoff member but vma->pgoff is of no use
information is the vma is for ANON.
By this patch, /proc/pid/maps shows just 0 if no file backing store.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
Index: mmotm-2.6.29-Jan13/fs/proc/task_mmu.c
===================================================================
--- mmotm-2.6.29-Jan13.orig/fs/proc/task_mmu.c
+++ mmotm-2.6.29-Jan13/fs/proc/task_mmu.c
@@ -220,7 +220,8 @@ static void show_map_vma(struct seq_file
 			flags & VM_WRITE ? 'w' : '-',
 			flags & VM_EXEC ? 'x' : '-',
 			flags & VM_MAYSHARE ? 's' : 'p',
-			((loff_t)vma->vm_pgoff) << PAGE_SHIFT,
+			(!vma->vm_file)? 0 :
+				((loff_t)vma->vm_pgoff) << PAGE_SHIFT,
 			MAJOR(dev), MINOR(dev), ino, &len);
 
 	/*
Index: mmotm-2.6.29-Jan13/fs/proc/task_nommu.c
===================================================================
--- mmotm-2.6.29-Jan13.orig/fs/proc/task_nommu.c
+++ mmotm-2.6.29-Jan13/fs/proc/task_nommu.c
@@ -143,7 +143,8 @@ static int nommu_vma_show(struct seq_fil
 		   flags & VM_WRITE ? 'w' : '-',
 		   flags & VM_EXEC ? 'x' : '-',
 		   flags & VM_MAYSHARE ? flags & VM_SHARED ? 'S' : 's' : 'p',
-		   (unsigned long long) vma->vm_pgoff << PAGE_SHIFT,
+		   (!vma->vm_file) ? 0 :
+			(unsigned long long) vma->vm_pgoff << PAGE_SHIFT,
 		   MAJOR(dev), MINOR(dev), ino, &len);
 
 	if (file) {

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