linux-ext4 - Re: [PATCH 09/12] ext4: simplify journal handling in ext4_setup_new_group

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Date:	Mon, 18 Jul 2011 11:21:04 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Tao Ma <tm@....ma>
Cc:	linux-ext4@...r.kernel.org, aedilger@...il.com
Subject: Re: [PATCH 09/12] ext4: simplify journal handling in ext4_setup_new_group_blocks

On Mon, Jul 18, 2011 at 11:09 AM, Tao Ma <tm@....ma> wrote:
> On 07/18/2011 10:52 AM, Yongqiang Yang wrote:
>> This patch simplifies journal handling in ext4_setup_new_group_blocks().
>>
>>
>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
>> ---
>>  fs/ext4/resize.c |   39 ++++++++++++++++++++-------------------
>>  1 files changed, 20 insertions(+), 19 deletions(-)
>>
>> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
>> index c91653c..ac5b63d 100644
>> --- a/fs/ext4/resize.c
>> +++ b/fs/ext4/resize.c
>> @@ -171,8 +171,7 @@ static struct buffer_head *bclean(handle_t *handle, struct super_block *sb,
>>   * If that fails, restart the transaction & regain write access for the
>>   * buffer head which is used for block_bitmap modifications.
>>   */
>> -static int extend_or_restart_transaction(handle_t *handle, int thresh,
>> -                                      struct buffer_head *bh)
>> +static int extend_or_restart_transaction(handle_t *handle, int thresh)
>>  {
>>       int err;
>>
>> @@ -183,9 +182,8 @@ static int extend_or_restart_transaction(handle_t *handle, int thresh,
>>       if (err < 0)
>>               return err;
>>       if (err) {
>> -             if ((err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA)))
>> -                     return err;
>> -             if ((err = ext4_journal_get_write_access(handle, bh)))
>> +             err = ext4_journal_restart(handle, EXT4_MAX_TRANS_DATA);
>> +             if (err)
>>                       return err;
> you removed an ext4_journal_get_write_access here, and I didn't see you
> add it back anywhere.
This get_write_access() was used to guarantee modification on the
block bitmap is in the new handle in previous code.  In previous code,
bitmap is modified everywhere in setup_group_blocks(),  actually, this
makes things complicated, in this patch, the modifications on block
bitmap are batched and are done by ext4_set_bits() after
extend_or_restart_transaction(), so it is ok.

Thanks,
Yongqiang.
>
> Thanks
> Tao
>>       }
>>
>> @@ -222,29 +220,24 @@ static int setup_new_group_blocks(struct super_block *sb,
>>
>>       BUG_ON(input->group != sbi->s_groups_count);
>>
>> -     if (IS_ERR(bh = bclean(handle, sb, input->block_bitmap))) {
>> -             err = PTR_ERR(bh);
>> -             goto exit_journal;
>> -     }
>> -
>>       /* Copy all of the GDT blocks into the backup in this group */
>>       for (i = 0, bit = 1, block = start + 1;
>>            i < gdblocks; i++, block++, bit++) {
>>               struct buffer_head *gdb;
>>
>>               ext4_debug("update backup group %#04llx (+%d)\n", block, bit);
>> -
>> -             if ((err = extend_or_restart_transaction(handle, 1, bh)))
>> -                     goto exit_bh;
>> +             err = extend_or_restart_transaction(handle, 1);
>> +             if (err)
>> +                     goto exit_journal;
>>
>>               gdb = sb_getblk(sb, block);
>>               if (!gdb) {
>>                       err = -EIO;
>> -                     goto exit_bh;
>> +                     goto exit_journal;
>>               }
>>               if ((err = ext4_journal_get_write_access(handle, gdb))) {
>>                       brelse(gdb);
>> -                     goto exit_bh;
>> +                     goto exit_journal;
>>               }
>>               lock_buffer(gdb);
>>               memcpy(gdb->b_data, sbi->s_group_desc[i]->b_data, gdb->b_size);
>> @@ -253,7 +246,7 @@ static int setup_new_group_blocks(struct super_block *sb,
>>               err = ext4_handle_dirty_metadata(handle, NULL, gdb);
>>               if (unlikely(err)) {
>>                       brelse(gdb);
>> -                     goto exit_bh;
>> +                     goto exit_journal;
>>               }
>>               brelse(gdb);
>>       }
>> @@ -264,7 +257,17 @@ static int setup_new_group_blocks(struct super_block *sb,
>>       err = sb_issue_zeroout(sb, gdblocks + start + 1, reserved_gdb,
>>                              GFP_NOFS);
>>       if (err)
>> -             goto exit_bh;
>> +             goto exit_journal;
>> +
>> +     err = extend_or_restart_transaction(handle, 2);
>> +     if (err)
>> +             goto exit_journal;
>> +
>> +     bh = bclean(handle, sb, input->block_bitmap);
>> +     if (IS_ERR(bh)) {
>> +             err = PTR_ERR(bh);
>> +             goto exit_journal;
>> +     }
>>
>>       if (ext4_bg_has_super(sb, input->group)) {
>>               ext4_debug("mark backup group tables %#04llx (+0)\n", start);
>> @@ -288,8 +291,6 @@ static int setup_new_group_blocks(struct super_block *sb,
>>       ext4_set_bits(bh->b_data, input->inode_table - start,
>>                     sbi->s_itb_per_group);
>>
>> -     if ((err = extend_or_restart_transaction(handle, 2, bh)))
>> -             goto exit_bh;
>>
>>       ext4_mark_bitmap_end(input->blocks_count, sb->s_blocksize * 8,
>>                            bh->b_data);
>
>



-- 
Best Wishes
Yongqiang Yang
--
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