linux-ext4 - Re: [PATCH 02/13] ext4: add a function which adds a new desc to a fs

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Date:	Wed, 10 Aug 2011 23:49:29 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Yongqiang Yang <xiaoqiangnk@...il.com>
Cc:	linux-ext4 List <linux-ext4@...r.kernel.org>,
	Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 02/13] ext4: add a function which adds a new desc to a fs

On 2011-08-10, at 9:28 PM, Yongqiang Yang wrote:
> This patch adds a function named ext4_add_new_desc() which adds
> a new desc to a fs and whose code is copied from ext4_group_add().
> 
> The function will be used by new resize implementation.

Similarly, this is duplicating a hunk of code from the middle of
ext4_group_add(), and instead of just adding a second copy of that
code, ext4_group_add() should be changed to call this new function
to avoid the code duplication.

> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
> ---
> fs/ext4/resize.c |   42 ++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 42 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index 6ffbdb6..4fcd515 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -735,6 +735,48 @@ exit_err:
> 	}
> }
> 
> +/*
> + * ext4_add_new_desc() adds group descriptor of group @group
> + *
> + * @handle: journal handle
> + * @sb; super block
> + * @group: the group no. of the first group desc to be added
> + * @resize_inode: the resize inode
> + */
> +static int ext4_add_new_desc(handle_t *handle, struct super_block *sb,
> +			     ext4_group_t group, struct inode *resize_inode)
> +{
> +	struct ext4_sb_info *sbi = EXT4_SB(sb);
> +	struct ext4_super_block *es = sbi->s_es;
> +	struct buffer_head *gdb_bh;
> +	int gdb_off, gdb_num, err = 0;
> +	int reserved_gdb = ext4_bg_has_super(sb, group) ?
> +		le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
> +
> +	gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
> +	gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
> +
> +	/*
> +	 * We will only either add reserved group blocks to a backup group
> +	 * or remove reserved blocks for the first group in a new group block.
> +	 * Doing both would be mean more complex code, and sane people don't
> +	 * use non-sparse filesystems anymore.  This is already checked above.
> +	 */
> +	if (gdb_off) {
> +		gdb_bh = sbi->s_group_desc[gdb_num];
> +		err = ext4_journal_get_write_access(handle, gdb_bh);
> +		if (err)
> +			goto out;
> +
> +		if (reserved_gdb && ext4_bg_num_gdb(sb, group))
> +			err = reserve_backup_gdb(handle, resize_inode, group);
> +	} else
> +		err = add_new_gdb(handle, resize_inode, group);
> +
> +out:
> +	return err;
> +}
> +
> /* Add group descriptor data to an existing or new group descriptor block.
>  * Ensure we handle all possible error conditions _before_ we start modifying
>  * the filesystem, because we cannot abort the transaction and not have it
> -- 
> 1.7.5.1
> 


Cheers, Andreas





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