Re: mdadm: can't removed failed/detached drives when using metadata 1.x

["Rémi Rérolle" <rrerolle@lacie.com>]

Le 14/02/2011 04:27, NeilBrown a écrit :
> On Thu, 10 Feb 2011 16:28:12 +0100 Rémi Rérolle<rrerolle@lacie.com>  wrote:
>
>> Hi Neil,
>>
>> I recently came across what I believe is a regression in mdadm, which
>> has been introduced in version 3.1.3.
>>
>> It seems that, when using metadata 1.x, the handling of failed/detached
>> drives isn't effective anymore.
>>
>> Here's a quick example:
>>
>> [root@GrosCinq ~]# mdadm -C /dev/md4 -l1 -n2 --metadata=1.0 /dev/sdc1
>> /dev/sdd1
>> mdadm: array /dev/md4 started.
>> [root@GrosCinq ~]#
>> [root@GrosCinq ~]# mdadm --wait /dev/md4
>> [root@GrosCinq ~]#
>> [root@GrosCinq ~]# mdadm -D /dev/md4
>> /dev/md4:
>>           Version : 1.0
>>     Creation Time : Thu Feb 10 13:56:31 2011
>>        Raid Level : raid1
>>        Array Size : 1953096 (1907.64 MiB 1999.97 MB)
>>     Used Dev Size : 1953096 (1907.64 MiB 1999.97 MB)
>>      Raid Devices : 2
>>     Total Devices : 2
>>       Persistence : Superblock is persistent
>>
>>       Update Time : Thu Feb 10 13:56:46 2011
>>             State : clean
>>    Active Devices : 2
>> Working Devices : 2
>>    Failed Devices : 0
>>     Spare Devices : 0
>>
>>              Name : GrosCinq:4  (local to host GrosCinq)
>>              UUID : bbfef508:252e7ce1:c95d4a03:8beb3cbd
>>            Events : 17
>>
>>       Number   Major   Minor   RaidDevice State
>>          0       8        1        0      active sync   /dev/sdc1
>>          1       8       49        1      active sync   /dev/sdd1
>>
>> [root@GrosCinq ~]# mdadm --fail /dev/md4 /dev/sdc1
>> mdadm: set /dev/sdc1 faulty in /dev/md4
>> [root@GrosCinq ~]#
>> [root@GrosCinq ~]# mdadm -D /dev/md4 | tail -n 6
>>
>>       Number   Major   Minor   RaidDevice State
>>          0       0        0        0      removed
>>          1       8       49        1      active sync   /dev/sdd1
>>
>>          0       8        1        -      faulty spare   /dev/sdc1
>> [root@GrosCinq ~]#
>> [root@GrosCinq ~]# mdadm --remove /dev/md4 failed
>> [root@GrosCinq ~]#
>> [root@GrosCinq ~]# mdadm -D /dev/md4 | tail -n 6
>>
>>       Number   Major   Minor   RaidDevice State
>>          0       0        0        0      removed
>>          1       8       49        1      active sync   /dev/sdd1
>>
>>          0       8        1        -      faulty spare   /dev/sdc1
>> [root@GrosCinq ~]#
>>
>> This is with mdadm 3.1.4, 3.1.3 or even 3.2, but not 3.1.2. I did a git
>> bisect to try and isolate the regression and it appears the guilty
>> commit is :
>>
>> b3b4e8a : "Avoid skipping devices where removing all faulty/detached
>>              devices."
>>
>> As stated in the commit, this is only true with metadata 1.x. With 0.9,
>> there is no problem. I also tested with detached drives as well as
>> raid5/6 and encountered the same issue. Actually, with detached drives,
>> it's even more annoying, since using --remove detached is the only way
>> to remove the device without restarting the array. For a failed drive,
>> there is still the possibility to use the device name.
>>
>> Do you have any idea of the reason behind that regression ? Shall this
>> patch only apply in the case of 0.9 metadata ?
>>
>> Regards,
>>
>
>
> Thanks for the report - especially for bitsecting it down to the erroneous
> commit!
>
> This patch should fix the regression.  I'll ensure it is in all future
> releases.
>

Hi Neil,

I've tested your patch with the setup that was causing me trouble. It 
did fix the regression.

Thanks!

Rémi

> Thanks,
> NeilBrown
>
>
> diff --git a/Manage.c b/Manage.c
> index 481c165..8c86a53 100644
> --- a/Manage.c
> +++ b/Manage.c
> @@ -421,7 +421,7 @@ int Manage_subdevs(char *devname, int fd,
>   				dnprintable = dvname;
>   				break;
>   			}
> -			if (jnext == 0)
> +			if (next != dv)
>   				continue;
>   		} else if (strcmp(dv->devname, "detached") == 0) {
>   			if (dv->disposition != 'r'&&  dv->disposition != 'f') {
> @@ -461,7 +461,7 @@ int Manage_subdevs(char *devname, int fd,
>   				dnprintable = dvname;
>   				break;
>   			}
> -			if (jnext == 0)
> +			if (next != dv)
>   				continue;
>   		} else if (strcmp(dv->devname, "missing") == 0) {
>   			if (dv->disposition != 'a' || dv->re_add == 0) {
>
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