Re: [PATCH] Btrfs: remove unnecessary code of chunk_root assignment in btrfs_read_chunk_tree.

From: Jeff Mahoney
Date: Mon Sep 05 2016 - 23:33:47 EST


On 9/5/16 11:05 PM, Jeff Mahoney wrote:
> On 9/5/16 3:56 AM, Qu Wenruo wrote:
>>
>>
>> At 09/05/2016 09:19 AM, Zhao Lei wrote:
>>> Hi, Sean Fu
>>>
>>>> From: Sean Fu [mailto:fxinrong@xxxxxxxxx]
>>>> Sent: Sunday, September 04, 2016 7:54 PM
>>>> To: dsterba@xxxxxxxx
>>>> Cc: clm@xxxxxx; anand.jain@xxxxxxxxxx; fdmanana@xxxxxxxx;
>>>> zhaolei@xxxxxxxxxxxxxx; linux-btrfs@xxxxxxxxxxxxxxx;
>>>> linux-kernel@xxxxxxxxxxxxxxx; Sean Fu <fxinrong@xxxxxxxxx>
>>>> Subject: [PATCH] Btrfs: remove unnecessary code of chunk_root
>>>> assignment in
>>>> btrfs_read_chunk_tree.
>>>>
>>>> The input argument root is already set with "fs_info->chunk_root".
>>>> "chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info)" in caller
>>>> "open_ctree".
>>>> âroot->fs_info = fs_infoâ in "btrfs_alloc_root".
>>>>
>>> The root argument of this function means "any root".
>>> And the function is designed getting chunk root from
>>> "any root" in head.
>>>
>>> Since there is only one caller of this function,
>>> and the caller always send chunk_root as root argument in
>>> current code, we can remove above conversion,
>>> and I suggest renaming root to chunk_root to make it clear,
>>> something like:
>>>
>>> - btrfs_read_chunk_tree(struct btrfs_root *root)
>>> + btrfs_read_chunk_tree(struct btrfs_root *chunk_root)
>>
>> Since root is only used to get fs_info->chunk_root, why not use fs_info
>> directly?
>
> Weird. Exactly this was a part of my fs_info patchset. I guess I need
> to go back and check what else is missing.

Actually, most of this didn't land. Pretty much anything that's a root
->fs_info conversion is in there.

-Jeff

> -Jeff
>
>
>> Thanks,
>> Qu
>>
>>>
>>> Thanks
>>> Zhaolei
>>>
>>>> Signed-off-by: Sean Fu <fxinrong@xxxxxxxxx>
>>>> ---
>>>> fs/btrfs/volumes.c | 2 --
>>>> 1 file changed, 2 deletions(-)
>>>>
>>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>>> index 366b335..384a6d2 100644
>>>> --- a/fs/btrfs/volumes.c
>>>> +++ b/fs/btrfs/volumes.c
>>>> @@ -6600,8 +6600,6 @@ int btrfs_read_chunk_tree(struct btrfs_root *root)
>>>> int ret;
>>>> int slot;
>>>>
>>>> - root = root->fs_info->chunk_root;
>>>> -
>>>> path = btrfs_alloc_path();
>>>> if (!path)
>>>> return -ENOMEM;
>>>> --
>>>> 2.6.2
>>>>
>>>
>>>
>>>
>>>
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>>
>>
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>
>


--
Jeff Mahoney
SUSE Labs

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