[PATCH] btrfs: remove the useless value assignment in block_rsv_release_bytes

[PATCH] btrfs: remove the useless value assignment in block_rsv_release_bytes

[xiakaixu1987]

From: Kaixu Xia <kaixuxia@tencent.com>

The variable qgroup_to_release is overwritten by the following if/else
statement before it is used, so this assignment is useless. Remove it.

Reported-by: Tosk Robot <tencent_os_robot@tencent.com>
Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
---
 fs/btrfs/block-rsv.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index bc920afe23bf..8638327069b7 100644
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -109,10 +109,8 @@ static u64 block_rsv_release_bytes(struct btrfs_fs_info *fs_info,
 	u64 ret;
 
 	spin_lock(&block_rsv->lock);
-	if (num_bytes == (u64)-1) {
+	if (num_bytes == (u64)-1)
 		num_bytes = block_rsv->size;
-		qgroup_to_release = block_rsv->qgroup_rsv_size;
-	}
 	block_rsv->size -= num_bytes;
 	if (block_rsv->reserved >= block_rsv->size) {
 		num_bytes = block_rsv->reserved - block_rsv->size;
-- 
2.20.0

Re: [PATCH] btrfs: remove the useless value assignment in block_rsv_release_bytes

[David Sterba]

On Sun, Nov 15, 2020 at 02:39:23PM +0800, xiakaixu1987@gmail.com wrote:
> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> The variable qgroup_to_release is overwritten by the following if/else
> statement before it is used, so this assignment is useless. Remove it.

Again this lacks explanation why removing it is correct.

Re: [PATCH] btrfs: remove the useless value assignment in block_rsv_release_bytes

[kaixuxia]

On 2020/11/16 23:15, David Sterba wrote:
> On Sun, Nov 15, 2020 at 02:39:23PM +0800, xiakaixu1987@gmail.com wrote:
>> From: Kaixu Xia <kaixuxia@tencent.com>
>>
>> The variable qgroup_to_release is overwritten by the following if/else
>> statement before it is used, so this assignment is useless. Remove it.
> 
> Again this lacks explanation why removing it is correct.
> 
Actually this assignment is redundant because the variable qgroup_to_release
has been overwritten before it is used. The logic like this,

 static u64 block_rsv_release_bytes(...)
 {
 ...
        if (num_bytes == (u64)-1) {
                num_bytes = block_rsv->size;
                qgroup_to_release = block_rsv->qgroup_rsv_size;
        }   
        
	//qgroup_to_release isn't used

        if (block_rsv->qgroup_rsv_reserved >= block_rsv->qgroup_rsv_size) {
                qgroup_to_release = block_rsv->qgroup_rsv_reserved -
                                    block_rsv->qgroup_rsv_size;
                block_rsv->qgroup_rsv_reserved = block_rsv->qgroup_rsv_size;
        } else {
                qgroup_to_release = 0;
        }//qgroup_to_release is overwritten    
 ...
 }

Thanks,
Kaixu

-- 
kaixuxia

Re: [PATCH] btrfs: remove the useless value assignment in block_rsv_release_bytes

[David Sterba]

On Tue, Nov 17, 2020 at 11:17:17AM +0800, kaixuxia wrote:
> 
> 
> On 2020/11/16 23:15, David Sterba wrote:
> > On Sun, Nov 15, 2020 at 02:39:23PM +0800, xiakaixu1987@gmail.com wrote:
> >> From: Kaixu Xia <kaixuxia@tencent.com>
> >>
> >> The variable qgroup_to_release is overwritten by the following if/else
> >> statement before it is used, so this assignment is useless. Remove it.
> > 
> > Again this lacks explanation why removing it is correct.
> > 
> Actually this assignment is redundant because the variable qgroup_to_release
> has been overwritten before it is used. The logic like this,

That's obvious and I did not mean that. Have you checked in which commit
the variable became unused and why? It's possible that it was indeed
just an oversight, but if not it could point to a bug.