[PATCH] ext2/ext3:useless code for return value

[PATCH] ext2/ext3:useless code for return value

["潘卫平(Peter Pan)"]

When rsv is the right hand side of goal, we should return NULL,
because now rsv's prev is NULL, or we return rsv.

Signed-off-by: Peter Pan(潘卫平) <wppan@redflag-linux.com>

---
 fs/ext2/balloc.c |    6 +-----
 fs/ext3/balloc.c |    6 +-----
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 3cf038c..023990f 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,
ext2_fsblk_t goal)
 	 * side of the interval containing the goal.  If it's the RHS,
 	 * we need to back up one.
 	 */
-	if (rsv->rsv_start > goal) {
-		n = rb_prev(&rsv->rsv_node);
-		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
-	}
-	return rsv;
+    return (rsv->rsv_start < goal) ? rsv : NULL;
 }

 /*
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index a177122..bfa62e9 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -310,11 +310,7 @@ search_reserve_window(struct rb_root *root,
ext3_fsblk_t goal)
 	 * side of the interval containing the goal.  If it's the RHS,
 	 * we need to back up one.
 	 */
-	if (rsv->rsv_start > goal) {
-		n = rb_prev(&rsv->rsv_node);
-		rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
-	}
-	return rsv;
+    return (rsv->rsv_start < goal) ? rsv : NULL;
 }

 /**
-- 
1.6.6


-- 
Peter Pan(潘卫平)
Red Flag Software Co.,Ltd
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Re: [PATCH] ext2/ext3:useless code for return value

[Jan Kara]

> When rsv is the right hand side of goal, we should return NULL,
> because now rsv's prev is NULL, or we return rsv.
> 
> Signed-off-by: Peter Pan(潘卫平) <wppan@redflag-linux.com>
> 
> ---
>  fs/ext2/balloc.c |    6 +-----
>  fs/ext3/balloc.c |    6 +-----
>  2 files changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 3cf038c..023990f 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,
> ext2_fsblk_t goal)
>  	 * side of the interval containing the goal.  If it's the RHS,
>  	 * we need to back up one.
>  	 */
> -	if (rsv->rsv_start > goal) {
> -		n = rb_prev(&rsv->rsv_node);
> -		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
> -	}
> -	return rsv;
> +    return (rsv->rsv_start < goal) ? rsv : NULL;
  Hmm, I'm not sure I understand your reasoning. Suppose we have an RB-tree
with two intervals 0-10, 20-30. Interval 0-10 is in the root. Now we search
for goal 15. In the root we go to right because 10<15, in the next node we go
to left because 15 < 20. Then the loop terminates. Now your code would return
NULL but previous code would return rb_prev of interval 20-30 which is 0-10.
And that is what we want as far as I understand what we expect from the
function...

								Honza
-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs
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Re: [PATCH] ext2/ext3:useless code for return value

["潘卫平(Peter Pan)"]

On 05/08/2010 12:23 AM, Jan Kara wrote:
>> When rsv is the right hand side of goal, we should return NULL,
>> because now rsv's prev is NULL, or we return rsv.
>>
>> Signed-off-by: Peter Pan(潘卫平)<wppan@redflag-linux.com>
>>
>> ---
>>   fs/ext2/balloc.c |    6 +-----
>>   fs/ext3/balloc.c |    6 +-----
>>   2 files changed, 2 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
>> index 3cf038c..023990f 100644
>> --- a/fs/ext2/balloc.c
>> +++ b/fs/ext2/balloc.c
>> @@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root,
>> ext2_fsblk_t goal)
>>   	 * side of the interval containing the goal.  If it's the RHS,
>>   	 * we need to back up one.
>>   	 */
>> -	if (rsv->rsv_start>  goal) {
>> -		n = rb_prev(&rsv->rsv_node);
>> -		rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node);
>> -	}
>> -	return rsv;
>> +    return (rsv->rsv_start<  goal) ? rsv : NULL;
>    Hmm, I'm not sure I understand your reasoning. Suppose we have an RB-tree
> with two intervals 0-10, 20-30. Interval 0-10 is in the root. Now we search
> for goal 15. In the root we go to right because 10<15, in the next node we go
> to left because 15<  20. Then the loop terminates. Now your code would return
> NULL but previous code would return rb_prev of interval 20-30 which is 0-10.
> And that is what we want as far as I understand what we expect from the
> function...
>
> 								Honza
You got the point!
Many thanks.

Regards
-- 
Peter Pan
Red Flag Software Co.,Ltd
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