Re: Re: [PATCH 1/4] md/raid5: Reduce one write-operation when handle badsector

[majianpeng <majianpeng@gmail.com>]

>On Thu, 28 Feb 2013 15:51:01 +0800 majianpeng <majianpeng@gmail.com> wrote:
>
>> For badsector,it took two steps:rewrite and reread.So for
>> write-operation,it make no sense to rewrite after write-operation.
>
>Please please please please please try to explain yourself better.
>
Sorry for that. 
>This patch doesn't make any sense.  The write succeeded.  We set the MadeGood
>flag so that later code will remove the block from the bad-block list.
>There will be no re-read or re-write.
>
For a striep which contain badsector is doing write-operation.
In analyse_stripe, it check badsector and set R5_ReadError.
 write--->MadeGood->clear badblock log. But it can't clear R5_ReadError flag.
So it will exec those code in func handle_stripe:
>        /* If the failed drives are just a ReadError, then we might need
>         * to progress the repair/check process
>         */
>        if (s.failed <= conf->max_degraded && !conf->mddev->ro)
>                for (i = 0; i < s.failed; i++) {
>                        struct r5dev *dev = &sh->dev[s.failed_num[i]];
>                        if (test_bit(R5_ReadError, &dev->flags)
>                            && !test_bit(R5_LOCKED, &dev->flags)
>                            && test_bit(R5_UPTODATE, &dev->flags)
>                                ) {  
>                                if (!test_bit(R5_ReWrite, &dev->flags)) {
>                                        set_bit(R5_Wantwrite, &dev->flags);
>                                        set_bit(R5_ReWrite, &dev->flags);
>                                        set_bit(R5_LOCKED, &dev->flags);
>                                        s.locked++;
>                                } else {
>                                        /* let's read it back */
>                                        set_bit(R5_Wantread, &dev->flags);
>                                       set_bit(R5_LOCKED, &dev->flags);
>                                       s.locked++;
>                                }    
>                        }    
>                }    

But the flag ReWrite can't set. So it do write-operatoin again.Then do read-operation.

Thanks!
Jianpeng Ma
>NeilBrown
>
>
>> 
>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
>> ---
>>  drivers/md/raid5.c |    4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
>> index 19d77a0..59c0569 100644
>> --- a/drivers/md/raid5.c
>> +++ b/drivers/md/raid5.c
>> @@ -1921,8 +1921,10 @@ static void raid5_end_write_request(struct bio *bi, int error)
>>  					&rdev->mddev->recovery);
>>  		} else if (is_badblock(rdev, sh->sector,
>>  				       STRIPE_SECTORS,
>> -				       &first_bad, &bad_sectors))
>> +				       &first_bad, &bad_sectors)) {
>>  			set_bit(R5_MadeGood, &sh->dev[i].flags);
>> +			set_bit(R5_ReWrite, &sh->dev[i].flags);
>> +		}
>>  	}
>>  	rdev_dec_pending(rdev, conf->mddev);
>>  
>
>