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

On 09/23, Robert Ho wrote:

quoted

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c

@@ -147,7 +147,7 @@ m_next_vma(struct proc_maps_private *priv, struct vm_area_struct *vma)
 static void m_cache_vma(struct seq_file *m, struct vm_area_struct *vma)
 {
 	if (m->count < m->size)	/* vma is copied successfully */
-		m->version = m_next_vma(m->private, vma) ? vma->vm_start : -1UL;
+		m->version = m_next_vma(m->private, vma) ? vma->vm_end : -1UL;
 }

OK.

quoted

 static void *m_start(struct seq_file *m, loff_t *ppos)

@@ -176,14 +176,14 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
 
 	if (last_addr) {
 		vma = find_vma(mm, last_addr);
-		if (vma && (vma = m_next_vma(priv, vma)))
+		if (vma)
 			return vma;
 	}

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".

	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 but at least
it would provide monotonic results. So definitely an improvement but
I guess we really want to document that only full reads provide a
consistent (at some moment in time) output.

-- 
Michal Hocko
SUSE Labs

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