linux-ext4 - Re: [PATCH 4/6] Use sb_issue_zeroout in setup_new_group

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Date:	Wed, 29 Sep 2010 16:12:16 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
cc:	linux-ext4@...r.kernel.org, tytso@....edu, rwheeler@...hat.com,
	sandeen@...hat.com, adilger@...ger.ca, snitzer@...il.com
Subject: Re: [PATCH 4/6] Use sb_issue_zeroout in setup_new_group_blocks

On Thu, 16 Sep 2010, Lukas Czerner wrote:

> Use sb_issue_zeroout to zero out inode table and descriptor table
> blocks instead of old approach which involves journaling.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> ---
>  fs/ext4/resize.c |   46 +++++++++++++---------------------------------
>  1 files changed, 13 insertions(+), 33 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index ca5c8aa..afba286 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -226,23 +226,13 @@ static int setup_new_group_blocks(struct super_block *sb,
>  	}
>  
>  	/* Zero out all of the reserved backup group descriptor table blocks */
> -	for (i = 0, bit = gdblocks + 1, block = start + bit;
> -	     i < reserved_gdb; i++, block++, bit++) {
> -		struct buffer_head *gdb;
> -
> -		ext4_debug("clear reserved block %#04llx (+%d)\n", block, bit);
> -
> -		if ((err = extend_or_restart_transaction(handle, 1, bh)))
> -			goto exit_bh;
> +	ext4_debug("clear inode table blocks %#04llx -> %#04llx\n",
> +			block, sbi->s_itb_per_group);
> +	err = sb_issue_zeroout(sb, gdblocks + start + 1, reserved_gdb,
> +			       GFP_NOFS, BLKDEV_IFL_WAIT);
> +	if (err)
> +		goto exit_journal;

When I look at this now, it seems it is bad, because when
sb_issue_discard() returns error for some reason we end up with not
released buffer_head. Since I am still not able to reproduce Ted's
errors I can't say whether it will help or not, but is doubt it will.

>  
> -		if (IS_ERR(gdb = bclean(handle, sb, block))) {
> -			err = PTR_ERR(gdb);
> -			goto exit_bh;
> -		}
> -		ext4_handle_dirty_metadata(handle, NULL, gdb);
> -		ext4_set_bit(bit, bh->b_data);
> -		brelse(gdb);
> -	}
>  	ext4_debug("mark block bitmap %#04llx (+%llu)\n", input->block_bitmap,
>  		   input->block_bitmap - start);
>  	ext4_set_bit(input->block_bitmap - start, bh->b_data);
> @@ -251,23 +241,13 @@ static int setup_new_group_blocks(struct super_block *sb,
>  	ext4_set_bit(input->inode_bitmap - start, bh->b_data);
>  
>  	/* Zero out all of the inode table blocks */
> -	for (i = 0, block = input->inode_table, bit = block - start;
> -	     i < sbi->s_itb_per_group; i++, bit++, block++) {
> -		struct buffer_head *it;
> -
> -		ext4_debug("clear inode block %#04llx (+%d)\n", block, bit);
> -
> -		if ((err = extend_or_restart_transaction(handle, 1, bh)))
> -			goto exit_bh;
> -
> -		if (IS_ERR(it = bclean(handle, sb, block))) {
> -			err = PTR_ERR(it);
> -			goto exit_bh;
> -		}
> -		ext4_handle_dirty_metadata(handle, NULL, it);
> -		brelse(it);
> -		ext4_set_bit(bit, bh->b_data);
> -	}
> +	block = input->inode_table;
> +	ext4_debug("clear inode table blocks %#04llx -> %#04llx\n",
> +			block, sbi->s_itb_per_group);
> +	err = sb_issue_zeroout(sb, block, sbi->s_itb_per_group,
> +			       GFP_NOFS, BLKDEV_IFL_WAIT);
> +	if (err)
> +		goto exit_journal;

here as well.

>  
>  	if ((err = extend_or_restart_transaction(handle, 2, bh)))
>  		goto exit_bh;
> 

I'll resend the patch shortly.

Thanks!
-Lukas
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