linux-ext4 - Re: [PATCH 25/31] e2fsck: Only release clusters when shortening a directory during a rehash

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Date:	Thu, 10 Oct 2013 18:13:15 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
cc:	tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 25/31] e2fsck: Only release clusters when shortening a
 directory during a rehash

On Mon, 30 Sep 2013, Darrick J. Wong wrote:

> Date: Mon, 30 Sep 2013 18:29:21 -0700
> From: Darrick J. Wong <darrick.wong@...cle.com>
> To: tytso@....edu, darrick.wong@...cle.com
> Cc: linux-ext4@...r.kernel.org
> Subject: [PATCH 25/31] e2fsck: Only release clusters when shortening a
>     directory during a rehash
> 
> When the rehash process is running on a bigalloc filesystem, it compresses all
> the directory entries and hash structures into the beginning of the directory
> file and then uses block_iterate3() to free the blocks off the end of the file.
> It seems to call ext2fs_block_alloc_stats2() for every block in a cluster,
> which is unfortunate because this function allocates and frees entire clusters
> (and updates the summary counts accordingly).  In this case e2fsck writes out
> incorrect summary counts.


Looks good.

Reviewed-by: Lukas Czerner <lczerner@...hat.com>

> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
>  e2fsck/rehash.c |   14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> 
> diff --git a/e2fsck/rehash.c b/e2fsck/rehash.c
> index 6ef3568..29da9a1 100644
> --- a/e2fsck/rehash.c
> +++ b/e2fsck/rehash.c
> @@ -719,10 +719,18 @@ static int write_dir_block(ext2_filsys fs,
>  		/* We don't need this block, so release it */
>  		e2fsck_read_bitmaps(wd->ctx);
>  		blk = *block_nr;
> -		ext2fs_unmark_block_bitmap2(wd->ctx->block_found_map, blk);
> -		ext2fs_block_alloc_stats2(fs, blk, -1);
> +		/*
> +		 * In theory, we only release blocks from the end of the
> +		 * directory file, so it's fine to clobber a whole cluster at
> +		 * once.
> +		 */
> +		if (blk % EXT2FS_CLUSTER_RATIO(fs) == 0) {
> +			ext2fs_unmark_block_bitmap2(wd->ctx->block_found_map,
> +						    blk);
> +			ext2fs_block_alloc_stats2(fs, blk, -1);
> +			wd->cleared++;
> +		}
>  		*block_nr = 0;
> -		wd->cleared++;
>  		return BLOCK_CHANGED;
>  	}
>  
> 
> --
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