[PATCH buf-fix] kernel, range: fix broken mtrr_cleanup

[PATCH buf-fix] kernel, range: fix broken mtrr_cleanup

[Shan Wei]

From: Samuel Liao <samuelliao@tencent.com>


commit fbe06b7bae7c9cf6ab05168fce5ee93b2f4bae7c broken the mtrr_cleanup
due to return incorrect merged range. this patch remove the empty range
by swapping with the last.

Error messages:
Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 64K         num_reg: 4      lose cover RAM: -0G
Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 128K        num_reg: 4      lose cover RAM: -0G
Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 256K        num_reg: 4      lose cover RAM: -0G
Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 512K        num_reg: 4      lose cover RAM: -0G


Signed-off-by: Samuel Liao <samuelliao@tencent.com>
---
 kernel/range.c | 15 ++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/kernel/range.c b/kernel/range.c
index eb911db..b723697 100644
--- a/kernel/range.c
+++ b/kernel/range.c
@@ -48,11 +48,18 @@ int add_range_with_merge(struct range *range, int az, int nr_range,
 		final_start = min(range[i].start, start);
 		final_end = max(range[i].end, end);
 
+		if (final_start == range[i].start && final_end == range[i].end)
+			return nr_range;
+
 		/* clear it and add it back for further merge */
-		range[i].start = 0;
-		range[i].end =  0;
-		return add_range_with_merge(range, az, nr_range,
-			final_start, final_end);
+		nr_range -= 1;
+		if (i != nr_range) {
+			range[i].start = range[nr_range].start;
+			range[i].end = range[nr_range].end;
+		}
+		range[nr_range].start = 0;
+		range[nr_range].end =  0;
+		i = -1;
 	}
 
 	/* Need to add it: */
-- 
1.8.2.1

Re: [PATCH buf-fix] kernel, range: fix broken mtrr_cleanup

[Yinghai Lu]

On Sun, Jun 9, 2013 at 2:42 AM, Shan Wei <shanwei88@gmail.com> wrote:
> From: Samuel Liao <samuelliao@tencent.com>
>
>
> commit fbe06b7bae7c9cf6ab05168fce5ee93b2f4bae7c broken the mtrr_cleanup
> due to return incorrect merged range. this patch remove the empty range
> by swapping with the last.
>
> Error messages:
> Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 64K         num_reg: 4      lose cover RAM: -0G
> Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 128K        num_reg: 4      lose cover RAM: -0G
> Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 256K        num_reg: 4      lose cover RAM: -0G
> Jun  9 14:06:18 kernel: [    0.000000] *BAD*gran_size: 64K   chunk_size: 512K        num_reg: 4      lose cover RAM: -0G
>
>
> Signed-off-by: Samuel Liao <samuelliao@tencent.com>
> ---
>  kernel/range.c | 15 ++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/range.c b/kernel/range.c
> index eb911db..b723697 100644
> --- a/kernel/range.c
> +++ b/kernel/range.c
> @@ -48,11 +48,18 @@ int add_range_with_merge(struct range *range, int az, int nr_range,
>                 final_start = min(range[i].start, start);
>                 final_end = max(range[i].end, end);
>
> +               if (final_start == range[i].start && final_end == range[i].end)
> +                       return nr_range;
> +
>                 /* clear it and add it back for further merge */
> -               range[i].start = 0;
> -               range[i].end =  0;
> -               return add_range_with_merge(range, az, nr_range,
> -                       final_start, final_end);
> +               nr_range -= 1;
> +               if (i != nr_range) {
> +                       range[i].start = range[nr_range].start;
> +                       range[i].end = range[nr_range].end;
> +               }
> +               range[nr_range].start = 0;
> +               range[nr_range].end =  0;
> +               i = -1;
>         }
>
>         /* Need to add it: */

this patch is totally wrong.

if the ranges already have [0,1g), [2g, 3g). and want to add [1g, 2g) to it.

what is the result after this patch?
only [1g, 2g)

Thanks

Yinghai

Re: [PATCH buf-fix] kernel, range: fix broken mtrr_cleanup(Internet mail)

[samuelliao(廖生苗)]

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I forget change final_start/final_end to start/end.  The old code add empty range in following case:

Before mtrr cleanup:
1. got initial MTRR range: 0-3G.
2. MTRR code try to merge 0-1M
3. result is 0-0, 0-3G,  total 2 range count

After cleanup:
1. got final MTRR range: 0-3G, total 1 range count

the cleanup code failed, because range count mismatch.
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