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

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