[PATCH] mm/memblock.c: fix index adjustment error in __next_mem_range_rev()

[<zijun_hu@htc.com>]

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Hi Tejun,

I am sorry, I don't take any test for the patch attached in previous mail, and it can't fix the bug completely, please ignore it
I provide a new patch attached in this mail which pass test and can fix the issue described below

__next_mem_range_rev() defined in mm/memblock.c doesn't Achieve desired purpose if parameter type_b ==NULL
This new patch can fix the issue and get the last reversed region contained in type_a rightly

The new patch is descripted as follows

From 0e242eda7696f176a9a2e585a1db01f0575b39c9 Mon Sep 17 00:00:00 2001
From: zijun_hu <zijun_hu@htc.com>
Date: Mon, 25 Jul 2016 15:06:57 +0800
Subject: [PATCH] mm/memblock.c: fix index adjustment error in
 __next_mem_range_rev()

fix region index adjustment error when parameter type_b of
__next_mem_range_rev() == NULL

Signed-off-by: zijun_hu <zijun_hu@htc.com>
---
 mm/memblock.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index ac12489..cc5aeab 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -991,7 +991,11 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 
 	if (*idx == (u64)ULLONG_MAX) {
 		idx_a = type_a->cnt - 1;
-		idx_b = type_b->cnt;
+		/* in order to get the last reversed region rightly */
+		if (type_b != NULL)
+			idx_b = type_b->cnt;
+		else
+			idx_b = 0;
 	}
 
 	for (; idx_a >= 0; idx_a--) {
@@ -1024,7 +1028,7 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 				*out_end = m_end;
 			if (out_nid)
 				*out_nid = m_nid;
-			idx_a++;
+			idx_a--;
 			*idx = (u32)idx_a | (u64)idx_b << 32;
 			return;
 		}
-- 
1.9.1

Zijun Hu
Tel: +86 021 3813 0008 Ext: 8556

F1 Building, 299 Kang Wei Road, Pudong New Area,
Shanghai 201315, China
htc.com



-----ÓʼþÔ­¼þ-----
·¢¼þÈË: Tejun Heo [mailto:htejun@gmail.com] ´ú±í Tejun Heo
·¢ËÍʱ¼ä: 2016Äê7ÔÂ26ÈÕ 2:52
ÊÕ¼þÈË: Zijun Hu(ºú×ÔÜŠ)
³­ËÍ: akpm@linux-foundation.org; kuleshovmail@gmail.com; ard.biesheuvel@linaro.org; tangchen@cn.fujitsu.com; weiyang@linux.vnet.ibm.com; dev@g0hl1n.net; david@gibson.dropbear.id.au; linux-mm@kvack.org; linux-kernel@vger.kernel.org
Ö÷Ìâ: Re: [PATCH] mm/memblock.c: fix index adjustment error in __next_mem_range_rev()

On Mon, Jul 25, 2016 at 07:34:12AM +0000, zijun_hu@htc.com wrote:
> Hi All,
>          There is a bug in mm/memblock.c
>          Could you review and phase-in this patch?
>          Thanks a lot
> 
> From 3abf1822d30f77f126bd7a3c09bb243d9c17a029 Mon Sep 17 00:00:00 2001
> From: zijun_hu <zijun_hu@htc.com>
> Date: Mon, 25 Jul 2016 15:06:57 +0800
> Subject: [PATCH] mm/memblock.c: fix index adjustment error in
> __next_mem_range_rev()
> 
> fix region index adjustment error when parameter type_b of
> __next_mem_range_rev() == NULL
> 
> Signed-off-by: zijun_hu <zijun_hu@htc.com>
> ---
> mm/memblock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c index ac12489..b14973e 
> 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1024,7 +1024,7 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
>                                  *out_end = m_end;
>                         if (out_nid)
>                                  *out_nid = m_nid;
> -                         idx_a++;
> +                        idx_a--;

Looks good to me.  Do you happen to have a test case for this bug?

Thanks.

--
tejun


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From 0e242eda7696f176a9a2e585a1db01f0575b39c9 Mon Sep 17 00:00:00 2001
From: zijun_hu <zijun_hu@htc.com>
Date: Mon, 25 Jul 2016 15:06:57 +0800
Subject: [PATCH] mm/memblock.c: fix index adjustment error in
 __next_mem_range_rev()

fix region index adjustment error when parameter type_b of
__next_mem_range_rev() == NULL

Signed-off-by: zijun_hu <zijun_hu@htc.com>
---
 mm/memblock.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index ac12489..cc5aeab 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -991,7 +991,11 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 
 	if (*idx == (u64)ULLONG_MAX) {
 		idx_a = type_a->cnt - 1;
-		idx_b = type_b->cnt;
+		/* in order to get the last reversed region rightly */
+		if (type_b != NULL)
+			idx_b = type_b->cnt;
+		else
+			idx_b = 0;
 	}
 
 	for (; idx_a >= 0; idx_a--) {
@@ -1024,7 +1028,7 @@ void __init_memblock __next_mem_range_rev(u64 *idx, int nid, ulong flags,
 				*out_end = m_end;
 			if (out_nid)
 				*out_nid = m_nid;
-			idx_a++;
+			idx_a--;
 			*idx = (u32)idx_a | (u64)idx_b << 32;
 			return;
 		}
-- 
1.9.1