From: Michel Lespinasse <walken@google.com>
Date: Thu, 29 Nov 2012 03:17:14 +0000 (+1100)
Subject: mm: check rb_subtree_gap correctness
X-Git-Tag: next-20121205~1^2~339
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=68bc521f08d5a2baeacb85318e393ac84afc7861;p=karo-tx-linux.git

mm: check rb_subtree_gap correctness

When CONFIG_DEBUG_VM_RB is enabled, check that rb_subtree_gap is correctly
set for every vma and that mm->highest_vm_end is also correct.

Also add an explicit 'bug' variable to track if browse_rb() detected any
invalid condition.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/mmap.c b/mm/mmap.c
index e8cd2b7deb66..bd56e8ee41a2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -336,7 +336,7 @@ static long vma_compute_subtree_gap(struct vm_area_struct *vma)
 #ifdef CONFIG_DEBUG_VM_RB
 static int browse_rb(struct rb_root *root)
 {
-	int i = 0, j;
+	int i = 0, j, bug = 0;
 	struct rb_node *nd, *pn = NULL;
 	unsigned long prev = 0, pend = 0;
 
@@ -344,23 +344,26 @@ static int browse_rb(struct rb_root *root)
 		struct vm_area_struct *vma;
 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
 		if (vma->vm_start < prev)
-			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1;
+			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), bug = 1;
 		if (vma->vm_start < pend)
-			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
+			printk("vm_start %lx pend %lx\n", vma->vm_start, pend), bug = 1;
 		if (vma->vm_start > vma->vm_end)
-			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
+			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start), bug = 1;
+		if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma))
+			printk("free gap %lx, correct %lx\n",
+			       vma->rb_subtree_gap,
+			       vma_compute_subtree_gap(vma)), bug = 1;
 		i++;
 		pn = nd;
 		prev = vma->vm_start;
 		pend = vma->vm_end;
 	}
 	j = 0;
-	for (nd = pn; nd; nd = rb_prev(nd)) {
+	for (nd = pn; nd; nd = rb_prev(nd))
 		j++;
-	}
 	if (i != j)
-		printk("backwards %d, forwards %d\n", j, i), i = 0;
-	return i;
+		printk("backwards %d, forwards %d\n", j, i), bug = 1;
+	return bug ? -1 : i;
 }
 
 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
@@ -379,6 +382,7 @@ void validate_mm(struct mm_struct *mm)
 {
 	int bug = 0;
 	int i = 0;
+	unsigned long highest_address = 0;
 	struct vm_area_struct *vma = mm->mmap;
 	while (vma) {
 		struct anon_vma_chain *avc;
@@ -386,11 +390,15 @@ void validate_mm(struct mm_struct *mm)
 		list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
 			anon_vma_interval_tree_verify(avc);
 		vma_unlock_anon_vma(vma);
+		highest_address = vma->vm_end;
 		vma = vma->vm_next;
 		i++;
 	}
 	if (i != mm->map_count)
 		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
+	if (highest_address != mm->highest_vm_end)
+		printk("mm->highest_vm_end %lx, found %lx\n",
+		       mm->highest_vm_end, highest_address), bug = 1;
 	i = browse_rb(&mm->mm_rb);
 	if (i != mm->map_count)
 		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;