linux-ext4 - Re: [PATCH 2/4] e2fsck: Do not forget to discard last block group

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Date:	Mon, 05 Mar 2012 13:29:19 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH 2/4] e2fsck: Do not forget to discard last block group

On 03/05/2012 01:49 AM, Lukas Czerner wrote:
> Previously when running e2fsck with '-E discard' argument the end of
> the last group has not been discarded. This patch fixes it so we
> always discard the end of the last group if needed.
> 
> This commit also removes unneeded argument from the
> e2fsck_discard_blocks(). Simultaneously the commit causes the block
> groups with BLOCK_UNINIT flag not to be discarded, which makes
> sense because we do not need to reclaim the space since so far
> there has not been written anything.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>

Reviewed-by: Eric Sandeen <sandeen@...hat.com>

As Phillip found, though, the part about any changes to BLOCK_UNINIT
behavior are pretty non-obvious, and could probably have used a more
verbose explanation in the changelog.

> ---
>  e2fsck/pass5.c |   24 ++++++++++++++++--------
>  1 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/e2fsck/pass5.c b/e2fsck/pass5.c
> index ee73dd5..37bbac2 100644
> --- a/e2fsck/pass5.c
> +++ b/e2fsck/pass5.c
> @@ -74,8 +74,8 @@ void e2fsck_pass5(e2fsck_t ctx)
>  	print_resource_track(ctx, _("Pass 5"), &rtrack, ctx->fs->io);
>  }
>  
> -static void e2fsck_discard_blocks(e2fsck_t ctx, io_manager manager,
> -				  blk64_t start, blk64_t count)
> +static void e2fsck_discard_blocks(e2fsck_t ctx, blk64_t start,
> +				  blk64_t count)
>  {
>  	ext2_filsys fs = ctx->fs;
>  
> @@ -85,7 +85,7 @@ static void e2fsck_discard_blocks(e2fsck_t ctx, io_manager manager,
>  	 * not enough to fix the problem, hence it is not safe to run discard
>  	 * in this case.
>  	 */
> -	if (ext2fs_test_changed(ctx->fs))
> +	if (ext2fs_test_changed(fs))
>  		ctx->options &= ~E2F_OPT_DISCARD;
>  
>  	if (!(ctx->options & E2F_OPT_NO) &&
> @@ -137,7 +137,7 @@ static void e2fsck_discard_inodes(e2fsck_t ctx, int group,
>  	num = count / EXT2_INODES_PER_BLOCK(fs->super);
>  
>  	if (num > 0)
> -		e2fsck_discard_blocks(ctx, fs->io->manager, blk, num);
> +		e2fsck_discard_blocks(ctx, blk, num);
>  }
>  
>  #define NO_BLK ((blk64_t) -1)
> @@ -377,16 +377,24 @@ redo_counts:
>  			free_blocks++;
>  			if (first_free > i)
>  				first_free = i;
> -		} else {
> -			if (i > first_free)
> -				e2fsck_discard_blocks(ctx, manager, first_free,
> -						      (i - first_free));
> +		} else if (i > first_free) {
> +			e2fsck_discard_blocks(ctx, first_free,
> +					      (i - first_free));
>  			first_free = ext2fs_blocks_count(fs->super);
>  		}
>  		blocks ++;
>  		if ((blocks == fs->super->s_clusters_per_group) ||
>  		    (EXT2FS_B2C(fs, i) ==
>  		     EXT2FS_B2C(fs, ext2fs_blocks_count(fs->super)-1))) {
> +			/*
> +			 * If the last block of this group is free, then we can
> +			 * discard it as well.
> +			 */
> +			if (i >= first_free)
> +				e2fsck_discard_blocks(ctx, first_free,
> +						      (i - first_free) + 1);
> +			first_free = ext2fs_blocks_count(fs->super);
> +
>  			free_array[group] = group_free;
>  			group ++;
>  			blocks = 0;

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