linux-ext4 - Re: [PATCH 01/13] ext4: add a function which extends a group without checking parameters

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Date:	Thu, 11 Aug 2011 14:27:41 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Andreas Dilger <adilger@...ger.ca>
Cc:	linux-ext4 List <linux-ext4@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH 01/13] ext4: add a function which extends a group without
 checking parameters

On Thu, Aug 11, 2011 at 1:47 PM, Andreas Dilger <adilger@...ger.ca> wrote:
> 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.
YES!  This needs some feedbacks, I thought the old resize interface
will be removed after the new resize interface goes into upstream.  So
I did not touch
old interface.  If we will remain the old interface, I can make some
patches which let old resize use common code instead.

Thank you for your review.
Yongqiang.
>
>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.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
>
>
>
>
>
>



-- 
Best Wishes
Yongqiang Yang
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