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

From: Sean Fu <fxinrong@gmail.com>
To: Jeff Mahoney <jeffm@suse.com>
Cc: dsterba@suse.cz, Qu Wenruo <quwenruo@cn.fujitsu.com>,
	Zhao Lei <zhaolei@cn.fujitsu.com>,
	clm@fb.com, anand.jain@oracle.com,
	Filipe Manana <FdManana@suse.com>,
	linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Btrfs: remove unnecessary code of chunk_root assignment in btrfs_read_chunk_tree.
Date: Sat, 10 Sep 2016 23:58:05 +0800	[thread overview]
Message-ID: <20160910155804.GB5659@linux-zmni.DHCP> (raw)
In-Reply-To: <e1d0adbb-922d-0778-a59d-6e6922c2ab68@suse.com>

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?

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