linux-mips
[Top] [All Lists]

Re: [PATCH 03/16] mm: check rb_subtree_gap correctness

To: Michel Lespinasse <walken@google.com>
Subject: Re: [PATCH 03/16] mm: check rb_subtree_gap correctness
From: Andrew Morton <akpm@linux-foundation.org>
Date: Tue, 6 Nov 2012 14:38:15 -0800
Cc: Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org, Russell King <linux@arm.linux.org.uk>, Ralf Baechle <ralf@linux-mips.org>, Paul Mundt <lethal@linux-sh.org>, "David S. Miller" <davem@davemloft.net>, Chris Metcalf <cmetcalf@tilera.com>, x86@kernel.org, William Irwin <wli@holomorphy.com>, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org
In-reply-to: <1352155633-8648-4-git-send-email-walken@google.com>
List-archive: <http://www.linux-mips.org/archives/linux-mips/>
List-help: <mailto:ecartis@linux-mips.org?Subject=help>
List-id: linux-mips <linux-mips.eddie.linux-mips.org>
List-owner: <mailto:ralf@linux-mips.org>
List-post: <mailto:linux-mips@linux-mips.org>
List-software: Ecartis version 1.0.0
List-subscribe: <mailto:ecartis@linux-mips.org?subject=subscribe%20linux-mips>
List-unsubscribe: <mailto:ecartis@linux-mips.org?subject=unsubscribe%20linux-mips>
References: <1352155633-8648-1-git-send-email-walken@google.com> <1352155633-8648-4-git-send-email-walken@google.com>
Sender: linux-mips-bounce@linux-mips.org
On Mon,  5 Nov 2012 14:47:00 -0800
Michel Lespinasse <walken@google.com> wrote:

> 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.
> 
> ...
>
> @@ -365,7 +365,7 @@ static void vma_rb_erase(struct vm_area_struct *vma, 
> struct rb_root *root)
>  #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;
>  
> @@ -373,29 +373,33 @@ 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;

OK, now who did that.  Whoever it was: stop it or you'll have your
kernel license revoked!

--- a/mm/mmap.c~mm-check-rb_subtree_gap-correctness-fix
+++ a/mm/mmap.c
@@ -372,16 +372,25 @@ static int browse_rb(struct rb_root *roo
        for (nd = rb_first(root); nd; nd = rb_next(nd)) {
                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), 
bug = 1;
-               if (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), bug = 1;
-               if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma))
+               if (vma->vm_start < prev) {
+                       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);
+                       bug = 1;
+               }
+               if (vma->vm_start > vma->vm_end) {
+                       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;
+                              vma_compute_subtree_gap(vma));
+                       bug = 1;
+               }
                i++;
                pn = nd;
                prev = vma->vm_start;
@@ -390,8 +399,10 @@ static int browse_rb(struct rb_root *roo
        j = 0;
        for (nd = pn; nd; nd = rb_prev(nd))
                j++;
-       if (i != j)
-               printk("backwards %d, forwards %d\n", j, i), bug = 1;
+       if (i != j) {
+               printk("backwards %d, forwards %d\n", j, i);
+               bug = 1;
+       }
        return bug ? -1 : i;
 }
 
@@ -411,14 +422,20 @@ void validate_mm(struct mm_struct *mm)
                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)
+       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;
+                      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;
+       if (i != mm->map_count) {
+               printk("map_count %d rb %d\n", mm->map_count, i);
+               bug = 1;
+       }
        BUG_ON(bug);
 }
 #else


<Prev in Thread] Current Thread [Next in Thread>