[PATCH] vfs: simply the code logic

[PATCH] vfs: simply the code logic

[zwu.kernel]

From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/block_dev.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index c2bbe1f..0f268d3 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -396,10 +396,7 @@ static loff_t block_llseek(struct file *file, loff_t offset, int origin)
 			goto out;
 	}
 	if (offset >= 0 && offset <= size) {
-		if (offset != file->f_pos) {
-			file->f_pos = offset;
-		}
-		retval = offset;
+		retval = file->f_pos = offset;
 	}
 out:
 	mutex_unlock(&bd_inode->i_mutex);
-- 
1.7.6

Re: [PATCH] vfs: simply the code logic

[Matthew Wilcox]

On Sat, Jul 21, 2012 at 11:38:19PM +0800, zwu.kernel@gmail.com wrote:
>  	if (offset >= 0 && offset <= size) {
> -		if (offset != file->f_pos) {
> -			file->f_pos = offset;
> -		}
> -		retval = offset;
> +		retval = file->f_pos = offset;
>  	}

But now you're writing to f_pos unconditionally.  That may cause
cacheline bouncing.  NAK.

Plus, you're now using a less-well-known feature of C, so while it's fewer
lines of code, it's not necessarily a simplification.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."