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

[Jeff Mahoney <jeffm@suse.com>]

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On 9/10/16 11:58 AM, Sean Fu wrote:
> On Thu, Sep 08, 2016 at 11:25:48PM -0400, Jeff Mahoney wrote:
>> On 9/8/16 11:08 PM, Sean Fu wrote:
>>> On Tue, Sep 06, 2016 at 11:12:20AM -0400, Jeff Mahoney wrote:
>>>> On 9/6/16 5:58 AM, David Sterba wrote:
>>>>> On Mon, Sep 05, 2016 at 11:13:40PM -0400, Jeff Mahoney wrote:
>>>>>>>> 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.
>>>>>
>>>>> Only half of the patchset has been merged so far because it did not pass
>>>>> testing, so I bisected to some point. I was about to let you know once
>>>>> most of 4.9 patches are prepared so there are less merge conflicts.
>>>>
>>>> Ok, thanks.  I was going to start the rebase today but I'll hold off
>>>> until you're set for 4.9.
>>>>
>>> Hi Jeff, Could you please share your patch? Where can i get it?
>>> I wanna have a look at it.
>>
>> Sure, it's the whole series that starts with this commit:
>> commit 160ceedfd40085cfb1e08305917fcc24cefdad93
>> Author: Jeff Mahoney <jeffm@suse.com>
>> Date:   Wed Aug 31 23:55:33 2016 -0400
>>
>>     btrfs: add dynamic debug support
>>
>> ... I still need to do clean up some commits that need merging.
>>
>> https://git.kernel.org/cgit/linux/kernel/git/jeffm/linux-btrfs.git/log/?h=btrfs-testing/kdave/misc-4.9/root-fsinfo-cleanup
>>
> Nice work. Thanks for your explaination.
> I have one more question about it.
> Although the total text size of this function is not changed, using
> fs_info should need one more instruction to get chunk_root field of
> fs_info than using chunk_root directly.
> Does it cause any performance impact?

I doubt it.  The caller had to do the dereference before.

-Jeff

> Sean
>> -Jeff
>>
>>
>>> Thanks
>>>> -Jeff
>>>>
>>>> -- 
>>>> Jeff Mahoney
>>>> SUSE Labs
>>>>
>>>
>>>
>>>
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>>
>>
>> -- 
>> Jeff Mahoney
>> SUSE Labs
>>
> 
> 
> 
> 


-- 
Jeff Mahoney
SUSE Labs


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