linux-ext4 - Re: [PATCH] ext4: start seraching for the right extent from the goal group.

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Message-ID: <48186CFB.8050206@redhat.com>
Date:	Wed, 30 Apr 2008 07:58:35 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	adilger@....com, linux-ext4@...r.kernel.org, cmm@...ibm.com,
	tytso@....edu
Subject: Re: [PATCH] ext4: start seraching for the right extent from the goal
 group.

Aneesh Kumar K.V wrote:
> With mballoc we search for the best extent using different
> criteria. We should always use the goal group when we are
> starting with a new criteria.

Aneesh, is there any testcase etc that will demonstrate the resulting
difference in layout?

It's not clear to me from this changelog (without looking at a lot more
context) exactly what you're changing and why...

thanks,
-eric

> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  fs/ext4/mballoc.c |   10 ++++++----
>  1 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 2a6c814..9b4cde7 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -1730,10 +1730,6 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>  		ac->ac_g_ex.fe_start = sbi->s_mb_last_start;
>  		spin_unlock(&sbi->s_md_lock);
>  	}
> -
> -	/* searching for the right group start from the goal value specified */
> -	group = ac->ac_g_ex.fe_group;
> -
>  	/* Let's just scan groups to find more-less suitable blocks */
>  	cr = ac->ac_2order ? 0 : 1;
>  	/*
> @@ -1743,6 +1739,12 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>  repeat:
>  	for (; cr < 4 && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
>  		ac->ac_criteria = cr;
> +		/*
> +		 * searching for the right group start
> +		 * from the goal value specified
> +		 */
> +		group = ac->ac_g_ex.fe_group;
> +
>  		for (i = 0; i < EXT4_SB(sb)->s_groups_count; group++, i++) {
>  			struct ext4_group_info *grp;
>  			struct ext4_group_desc *desc;

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