On Thu 29-09-16 21:14:40, Robert Hu wrote:

On Mon, 2016-09-26 at 10:46 +0200, Michal Hocko wrote:

quoted

On Fri 23-09-16 17:53:51, Oleg Nesterov wrote:

quoted

On 09/23, Michal Hocko wrote:

quoted

On Fri 23-09-16 15:56:36, Oleg Nesterov wrote:

quoted

I think we can simplify this patch. And imo make it better. How about

it is certainly less subtle because it doesn't report "sub-vmas".

quoted

	if (last_addr) {
		vma = find_vma(mm, last_addr - 1);
		if (vma && vma->vm_start <= last_addr)
			vma = m_next_vma(priv, vma);
		if (vma)
			return vma;
	}

we would still miss a VMA if the last one got shrunk/split

Not sure I understand what you mean... If the last one was split
we probably should not report the new vma.

Right, VMA split is less of a problem. I meant to say that if the
last_vma->vm_end got lower for whatever reason then we could miss a VMA
right after. We actually might want to display such a VMA because it
could be a completely new one. We just do not know whether it is a
former split with enlarged VMA or a completely new one

[      old VMA     ]   Hole       [   VMA    ]
[ old VMA   ][  New VMa    ]      [   VMA    ]

This is indeed possible. But I see this is like the last_vma enlargement
case. I suggest we accept such missing, as we accept the enlargement
part of last_vma is not printed.

How about we set such target:

0) consistent output can be achieved only in the single read call

1) no duplicate print; 2) no old vma
missing (unless it's unmapped); 3) monotonic printing.
We accept those newly added/changed parts between 2 partial reads is not
printed.

OK
-- 
Michal Hocko
SUSE Labs

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