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Date:	Tue, 5 Apr 2011 13:02:24 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4:Fix credits computing for indirect mapped files.

On Tue, Apr 5, 2011 at 3:39 AM, Ted Ts'o <tytso@....edu> wrote:
> On Fri, Mar 25, 2011 at 09:10:05PM +0800, Yongqiang Yang wrote:
>> Either the first block or the last one could be not aligned with
>> block boundary, 1 block is needed to fix it.
>>
>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
>
> Thanks for the patch submission!
>
> I further modified the patch to make the commit description a bit
> clearer, and to fix an additional bug that I noticed while reviewing
> your patch.
Thank you.

Yongqiang.
>
>                                        - Ted
>
> From fa0dfea6882a833a70f04b3089a751f75c0d03f6 Mon Sep 17 00:00:00 2001
> From: Yongqiang Yang <xiaoqiangnk@...il.com>
> Date: Mon, 4 Apr 2011 15:38:38 -0400
> Subject: [PATCH] ext4: fix credits computing for indirect mapped files
>
> When writing a contiguous set of blocks, two indirect blocks could be
> needed depending on how the blocks are aligned, so we need to increase
> the number of credits needed by one.
>
> [ Also fixed a another bug which could further underestimate the
>  number of journal credits needed by 1; the code was using integer
>  division instead of DIV_ROUND_UP() -- tytso]
>
> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  fs/ext4/inode.c |   11 +++++------
>  1 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 1a86282..7d11e02 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5398,13 +5398,12 @@ static int ext4_indirect_trans_blocks(struct inode *inode, int nrblocks,
>        /* if nrblocks are contiguous */
>        if (chunk) {
>                /*
> -                * With N contiguous data blocks, it need at most
> -                * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) indirect blocks
> -                * 2 dindirect blocks
> -                * 1 tindirect block
> +                * With N contiguous data blocks, we need at most
> +                * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
> +                * 2 dindirect blocks, and 1 tindirect block
>                 */
> -               indirects = nrblocks / EXT4_ADDR_PER_BLOCK(inode->i_sb);
> -               return indirects + 3;
> +               return DIV_ROUND_UP(nrblocks,
> +                                   EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
>        }
>        /*
>         * if nrblocks are not contiguous, worse case, each block touch
> --
> 1.7.3.1
>
>



-- 
Best Wishes
Yongqiang Yang
--
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