From: Andreas Dilger <adilger@dilger.ca>
Subject: Re: [PATCH 01/13] ext4: add a function which extends a group without checking parameters
Date: Wed, 10 Aug 2011 23:47:05 -0600
Message-ID: <4B3266BE-B083-41DE-BD85-BA1497D9EF51@dilger.ca>
References: <1313033308-882-1-git-send-email-xiaoqiangnk@gmail.com> <1313033308-882-2-git-send-email-xiaoqiangnk@gmail.com>
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Cc: linux-ext4 List <linux-ext4@vger.kernel.org>,
	Theodore Ts'o <tytso@mit.edu>
To: Yongqiang Yang <xiaoqiangnk@gmail.com>
In-Reply-To: <1313033308-882-2-git-send-email-xiaoqiangnk@gmail.com>
Sender: linux-ext4-owner@vger.kernel.org

On 2011-08-10, at 9:28 PM, Yongqiang Yang wrote:
> This patch added a function named __ext4_group_extend() whose code
> is copied from ext4_group_extend().  __ext4_group_extend() assumes
> the parameter is valid and has been checked by caller.
> 
> __ext4_group_extend() will be used by new resize implementation. It
> can also be used by ext4_group_extend(), but this patch series does
> not do this.

Since this is duplicating a lot of code from ext4_group_extend(), this
patch should be written in such a way that this new function is added,
and the duplicate code is removed from ext4_group_extend() and calls
the new function instead.

It looks like all of these patches are adding a completely duplicate set
of functions for doing the resizing, even though they are largely the
same as the existing code, and it will mean duplicate efforts to maintain
both copies of the code.

> Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
> ---
> fs/ext4/resize.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 53 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index 707d3f1..6ffbdb6 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -969,6 +969,59 @@ exit_put:
> } /* ext4_group_add */
> 
> /*
> + * extend a group without checking assuming that checking has been done.
> + */
> +static int __ext4_group_extend(struct super_block *sb,
> +			       ext4_fsblk_t o_blocks_count, ext4_grpblk_t add)
> +{
> +	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
> +	handle_t *handle;
> +	int err = 0, err2;
> +
> +	/* We will update the superblock, one block bitmap, and
> +	 * one group descriptor via ext4_ext4_group_add_blocks().

Typo here: "ext4_ext4"

> +	 */
> +	handle = ext4_journal_start_sb(sb, 3);
> +	if (IS_ERR(handle)) {
> +		err = PTR_ERR(handle);
> +		ext4_warning(sb, "error %d on journal start", err);
> +		goto out;
> +	}
> +
> +	err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
> +	if (err) {
> +		ext4_warning(sb, "error %d on journal write access", err);
> +		ext4_journal_stop(handle);
> +		goto out;
> +	}
> +
> +	ext4_blocks_count_set(es, o_blocks_count + add);
> +	ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,
> +		   o_blocks_count + add);
> +	/* We add the blocks to the bitmap and set the group need init bit */
> +	err = ext4_group_add_blocks(handle, sb, o_blocks_count, add);
> +	if (err)
> +		goto exit_journal;
> +	ext4_handle_dirty_super(handle, sb);
> +	ext4_debug("freed blocks %llu through %llu\n", o_blocks_count,
> +		   o_blocks_count + add);
> +exit_journal:
> +	err2 = ext4_journal_stop(handle);
> +	if (err2 && !err)
> +		err = err2;
> +
> +	if (!err) {
> +		if (test_opt(sb, DEBUG))
> +			printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
> +			       "blocks\n", ext4_blocks_count(es));
> +		update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr, (char *)es,
> +			       sizeof(struct ext4_super_block));
> +	}
> +out:
> +	return err;
> +}
> +
> +/*
>  * Extend the filesystem to the new number of blocks specified.  This entry
>  * point is only used to extend the current filesystem to the end of the last
>  * existing group.  It can be accessed via ioctl, or by "remount,resize=<size>"
> -- 
> 1.7.5.1
> 


Cheers, Andreas