linux-ext4 - Re: [PATCH 2/2] ext4: avoid finding next leaf if newext->ee_block smaller than fex->ee

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Date:	Tue, 12 Jul 2011 09:33:26 +0800
From:	Robin Dong <hao.bigrat@...il.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Yongqiang Yang <xiaoqiangnk@...il.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] ext4: avoid finding next leaf if newext->ee_block
 smaller than fex->ee_block

2011/7/12 Ted Ts'o <tytso@....edu>:
> On Thu, Jun 30, 2011 at 04:42:31PM +0800, Yongqiang Yang wrote:
>> How about:
>>            next = EXT_MAX_BLOCKS;
>>            if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block)
>>                    next = ext4_ext_next_leaf_block(inode, path);
>>            if (next != EXT_MAX_BLOCKS) {
>
> Agreed, that's a better way of doing things.  Also, Robin, please
> compare and contrast your description with mine.  The commit
> description shouldn't just be a textual description of the change.  It
> should give the larger context of the change and why it's important.
>
>                                       - Ted
>
> commit 2a3f7e0e0e55f8817fbe92d111ef2a06e6b8ef18
> Author: Robin Dong <sanbai@...bao.com>
> Date:   Mon Jul 11 15:43:38 2011 -0400
>
>    ext4: avoid unneeded ext4_ext_next_leaf_block() while inserting extents
>
>    Optimize ext4_exT_insert_extent() by avoiding
>    ext4_ext_next_leaf_block() when the result is not used/needed.
>
>    Signed-off-by: Robin Dong <sanbai@...bao.com>
>    Signed-off-by: "Theodore Ts'o" <tytso@....edu>
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 9cbdcb2..f1c538e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1730,9 +1730,10 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
>
>        /* probably next leaf has space for us? */
>        fex = EXT_LAST_EXTENT(eh);
> -       next = ext4_ext_next_leaf_block(inode, path);
> -       if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block)
> -           && next != EXT_MAX_BLOCKS) {
> +       next = EXT_MAX_BLOCKS;
> +       if (le32_to_cpu(newext->ee_block) > le32_to_cpu(fex->ee_block))
> +               next = ext4_ext_next_leaf_block(inode, path);
> +       if (next != EXT_MAX_BLOCKS) {
>                ext_debug("next leaf block - %d\n", next);
>                BUG_ON(npath != NULL);
>                npath = ext4_ext_find_extent(inode, next, NULL);
>

It seems much better than my description. Thanks!

-- 
--
Best Regard
Robin Dong
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