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

[Sean Fu <fxinrong@gmail.com>]

On Mon, Sep 05, 2016 at 03:56:41PM +0800, Qu Wenruo wrote:
> 
> 
> At 09/05/2016 09:19 AM, Zhao Lei wrote:
> >Hi, Sean Fu
> >
> >>From: Sean Fu [mailto:fxinrong@gmail.com]
> >>Sent: Sunday, September 04, 2016 7:54 PM
> >>To: dsterba@suse.com
> >>Cc: clm@fb.com; anand.jain@oracle.com; fdmanana@suse.com;
> >>zhaolei@cn.fujitsu.com; linux-btrfs@vger.kernel.org;
> >>linux-kernel@vger.kernel.org; Sean Fu <fxinrong@gmail.com>
> >>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".
> >>“root->fs_info = fs_info” 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?
Sorry for late reply.
chunk_root is processed in btrfs_read_chunk_tree.
Why should we pass fs_info directly to btrfs_read_chunk_tree?
Could you give me more detail?

Many thanks
> 
> Thanks,
> Qu
> 
> >
> >Thanks
> >Zhaolei
> >
> >>Signed-off-by: Sean Fu <fxinrong@gmail.com>
> >>---
> >> 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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> >
> 
>