linux-kernel - Re: [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: <20090115114312.e42a0dba.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 15 Jan 2009 11:43:12 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Mike Waychison <mikew@...gle.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, yinghan@...gle.com
Subject: Re: [RFC][PATCH] don't show pgoff of vma if vma is pure ANON (was
 Re: mmotm 2009-01-12-16-53 uploaded)

On Wed, 14 Jan 2009 14:08:35 +0000 (GMT)
Hugh Dickins <hugh@...itas.com> wrote:

> On Wed, 14 Jan 2009, KAMEZAWA Hiroyuki wrote:
> > 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>
> > ---
> 
> Brutal, but sensible enough: revert to how things looked before
> we ever starting putting vm_pgoff to work on anonymous areas.
> 
> I slightly regret losing that visible clue to whether an anonymous
> vma has ever been mremap moved.  But have I ever actually used that
> info?  No, never.
> 
> I presume you test !vma->vm_file so the lines fit in, fair enough.
> But I think you'll find checkpatch.pl protests at "(!vma->vm_file)?"
> 
> I dislike its decisions on the punctuation of the ternary operator
> - perhaps even more than Andrew dislikes the operator itself!
> Do we write a space before a question mark? no: nor before a colon;
> but I also dislike getting into checkpatch.pl arguments!
> 
> While you're there, I'd also be inclined to make task_nommu.c
> use the same loff_t cast as task_mmu.c is using.
> 
Ok, I'll try to update to reasonable style.

Thanks,
-Kame


> Hugh
> 
> > 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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