Patchwork [25/31] e2fsck: Only release clusters when shortening a directory during a rehash

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Submitter Darrick J. Wong
Date Oct. 1, 2013, 1:29 a.m.
Message ID <20131001012921.28415.90047.stgit@birch.djwong.org>
Download mbox | patch
Permalink /patch/279304/
State Superseded
Headers show

Comments

Darrick J. Wong - Oct. 1, 2013, 1:29 a.m.
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.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 e2fsck/rehash.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)



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Lukas Czerner - Oct. 10, 2013, 4:13 p.m.
On Mon, 30 Sep 2013, Darrick J. Wong wrote:

> Date: Mon, 30 Sep 2013 18:29:21 -0700
> From: Darrick J. Wong <darrick.wong@oracle.com>
> To: tytso@mit.edu, darrick.wong@oracle.com
> Cc: linux-ext4@vger.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@redhat.com>

> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.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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Patch

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;
 	}