* [PATCH] ext4: use swap macro in mext_page_double_lock
@ 2018-07-09 13:16 Gustavo A. R. Silva
2018-07-22 22:19 ` Theodore Y. Ts'o
0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2018-07-09 13:16 UTC (permalink / raw)
To: Theodore Ts'o, Andreas Dilger
Cc: linux-ext4, linux-kernel, Gustavo A. R. Silva
Make use of the swap macro and remove unnecessary variable *tmp*.
This makes the code easier to read and maintain. Also, reduces the
stack usage.
This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
fs/ext4/move_extent.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 8e17efd..a409ff7 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -134,9 +134,7 @@ mext_page_double_lock(struct inode *inode1, struct inode *inode2,
mapping[0] = inode1->i_mapping;
mapping[1] = inode2->i_mapping;
} else {
- pgoff_t tmp = index1;
- index1 = index2;
- index2 = tmp;
+ swap(index1, index2);
mapping[0] = inode2->i_mapping;
mapping[1] = inode1->i_mapping;
}
--
2.7.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] ext4: use swap macro in mext_page_double_lock
2018-07-09 13:16 [PATCH] ext4: use swap macro in mext_page_double_lock Gustavo A. R. Silva
@ 2018-07-22 22:19 ` Theodore Y. Ts'o
2018-07-22 23:30 ` Gustavo A. R. Silva
0 siblings, 1 reply; 3+ messages in thread
From: Theodore Y. Ts'o @ 2018-07-22 22:19 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: Andreas Dilger, linux-ext4, linux-kernel
On Mon, Jul 09, 2018 at 08:16:00AM -0500, Gustavo A. R. Silva wrote:
> Make use of the swap macro and remove unnecessary variable *tmp*.
> This makes the code easier to read and maintain. Also, reduces the
> stack usage.
>
> This code was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
It doesn't actually reduce stack usage. Look at the definition of
swap() in include/linux/kernel.h:
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
It removes the variable "tmp", and replace it with "__tmp".
It slightly reduces the number of lines of code, so it slightly makes
the code easier to maintainer. But I think you are really
over-promising how much this commit helps.
Regards,
- Ted
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] ext4: use swap macro in mext_page_double_lock
2018-07-22 22:19 ` Theodore Y. Ts'o
@ 2018-07-22 23:30 ` Gustavo A. R. Silva
0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2018-07-22 23:30 UTC (permalink / raw)
To: Theodore Y. Ts'o, Andreas Dilger, linux-ext4, linux-kernel
Hi Theodore,
On 07/22/2018 05:19 PM, Theodore Y. Ts'o wrote:
> On Mon, Jul 09, 2018 at 08:16:00AM -0500, Gustavo A. R. Silva wrote:
>> Make use of the swap macro and remove unnecessary variable *tmp*.
>> This makes the code easier to read and maintain. Also, reduces the
>> stack usage.
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>
> It doesn't actually reduce stack usage. Look at the definition of
> swap() in include/linux/kernel.h:
>
> #define swap(a, b) \
> do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
>
> It removes the variable "tmp", and replace it with "__tmp".
>
> It slightly reduces the number of lines of code, so it slightly makes
> the code easier to maintainer. But I think you are really
> over-promising how much this commit helps.
>
I'll remove that part from the changelog and send it again.
Thanks
--
Gustavo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-07-09 13:16 [PATCH] ext4: use swap macro in mext_page_double_lock Gustavo A. R. Silva
2018-07-22 22:19 ` Theodore Y. Ts'o
2018-07-22 23:30 ` Gustavo A. R. Silva
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