From mboxrd@z Thu Jan 1 00:00:00 1970 From: Romu Hu Subject: Re: RHEL6.6 dm-cache and dm-era Date: Thu, 25 Sep 2014 14:10:40 +0800 Message-ID: <5423B1E0.4000400@gmail.com> References: <54164DC0.3020907@gmail.com> <541A977D.7010108@gmail.com> <6FC8490A-55CA-454E-83FE-061A33FDE8DE@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1167603575195438170==" Return-path: In-Reply-To: <6FC8490A-55CA-454E-83FE-061A33FDE8DE@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: dm-devel@redhat.com List-Id: dm-devel.ids This is a multi-part message in MIME format. --===============1167603575195438170== Content-Type: multipart/alternative; boundary="------------030801090504030707030707" This is a multi-part message in MIME format. --------------030801090504030707030707 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit On 2014/9/24 12:10, Brassow Jonathan wrote: > On Sep 22, 2014, at 7:35 AM, Romu wrote: > >> I tried the following command to set up my era target but the command >> immediately panics the system and the system reboots. >> >> # dmsetup create MyEra --table "0 41941903 era >> /dev/mapper/VG-CacheDataLV_cmeta /dev/mapper/VG-OriginLV 4096" >> >> The metadata dev and the origin dev are all part of a LVM cache LV. >> VG-CacheDataLV_cmeta is the cache metadata LV on the smaller and >> faster device, VG-OriginLV is the origin LV on the faster and slower >> device, 41941903 is the total sector number of the device of OriginLV >> (the LV takes 100% space of the device), 4096 is the block size of >> OriginLV, I have run 'mkfs.ext4 /dev/mapper/VG-OriginLV' before >> running the dmsetup command. >> >> Below is the message in /var/log/messages after running the dmsetup >> comnmand: >> >> kernel: device-mapper: era: sb_check failed: magic 1623043: wanted >> 2126579579 >> kernel: device-mapper: block manager: superblock validator check >> failed for block 0 >> kernel: device-mapper: era: couldn't read_lock superblock >> >> >> Any idea? >> > > Sorry, I haven't used dm-era yet. However, it does appear that you > are perhaps specifying the wrong devices when creating the era device? > Looks like you might be allowing the era target and the cache target > to use the same metadata area at the same time - causing them to > corrupt each other's metadata area? > > brassow I think the dmsetup command to set up an era target should be something like this: # dmsetup create MyEra --table "0 sector_number era metadeta_dev origin_dev block_size" My questions: 1) How to calculate sector_number? According to https://www.kernel.org/doc/Documentation/device-mapper/era.txt, I guess it should be (4 * nr_blocks) bytes + buffers, but what is nr_blocks and what is buffers? 2) Any documentation for dmsetup tables? 3) Both my metadata_dev and origin_dev are 10G partitions, is this all right? 4) My origin_dev is a ext4 filesystem with a block size of 4096, so the block_size in the command line should also be 4096? I tried the following command: # dmsetup create MyEra --table "0 160000 era /dev/mapper/mpathap1 /dev/mapper/mpathbp1 4096" It immediately panics the kernel (2.6.32-494.el6.i686) with the following info in /var/log/messages: Sep 24 22:44:22 localhost kernel: device-mapper: era: sb_check failed: magic 0: wanted 2126579579 Sep 24 22:44:22 localhost kernel: device-mapper: block manager: superblock validator check failed for block 0 Sep 24 22:44:22 localhost kernel: device-mapper: era: couldn't read_lock superblock Sep 24 22:44:22 localhost kernel: BUG: unable to handle kernel NULL pointer dereference at 00000008 Sep 24 22:44:22 localhost kernel: IP: [] era_destroy+0x7/0x60 [dm_era] Sep 24 22:44:22 localhost kernel: *pdpt = 0000000001945001 *pde = 00000003ff97f067 Sep 24 22:44:22 localhost kernel: Oops: 0000 [#1] SMP Sep 24 22:44:22 localhost kernel: last sysfs file: /sys/module/dm_mod/initstate Thanks Romu --------------030801090504030707030707 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by mx4-phx2.redhat.com id s8P6B3Q0028558 On 2014/9/24 12:10, Brassow Jonathan wrote:
On Sep 22, 2014, at 7:35 AM, Romu wrote:

I tried the following command to set up my era target but the command immediately panics the system and the system reboots.

# dmsetup create MyEra --table "0 41941903=A0era /dev/mapper/VG-CacheDataLV_cmeta /dev/mapper/VG-OriginLV 4096"

The metadata dev and the origin dev are all part of a LVM cache LV.=A0 VG-CacheDataLV_cmeta is the=A0cache metada= ta LV on the smaller and faster device, VG-OriginLV is the origin LV on the faster and slower device, 41941903 is the total sector number of the device of OriginLV (the LV takes 100% space of the device), 4096 is the block size of OriginLV, I have run 'mkfs.ext4 /dev/mapper/VG-OriginLV' before running the dmsetup command.

Below is the message in /var/log/messages after running the dmsetup comnmand:

kernel: device-mapper: era: sb_check failed: magic 1623043: wanted 2126579579
kernel: device-mapper: block manager: superblock validator check failed for block 0
kernel: device-mapper: era: couldn't read_lock superblock


Any idea?


Sorry, I haven't used dm-era yet. =A0However, it does appear that you are perhaps specifying the wrong devices when creating the era device? =A0Looks like you might be allowing the era targe= t and the cache target to use the same metadata area at the same time - causing them to corrupt each other's metadata area?

=A0brassow

I think the dmsetup command to set up an era target should be something like this:

# dmsetup create MyEra --table "0 sector_number era metadeta_dev origin_dev block_size"

My questions:

1) How to calculate sector_number?=A0 According to https://www.kernel.org/doc/Document= ation/device-mapper/era.txt, I guess it should be (4 * nr_blocks) bytes + buffers, but what is nr_blocks and what is buffers?
2) Any documentation for dmsetup tables?
3) Both my metadata_dev and origin_dev are 10G partitions, is this all right?
4) My origin_dev is a ext4 filesystem with a block size of 4096, so the block_size in the command line should also be 4096?

I tried the following command:

# dmsetup create MyEra --table "0 160000 era /dev/mapper/mpathap1 /dev/mapper/mpathbp1 4096"

It immediately panics the kernel (2.6.32-494.el6.i686) with the following info in /var/log/messages:

Sep 24 22:44:22 localhost kernel: device-mapper: era: sb_check failed: magic 0: wanted 2126579579
Sep 24 22:44:22 localhost kernel: device-mapper: block manager: superblock validator check failed for block 0
Sep 24 22:44:22 localhost kernel: device-mapper: era: couldn't read_lock superblock
Sep 24 22:44:22 localhost kernel: BUG: unable to handle kernel NULL pointer dereference at 00000008
Sep 24 22:44:22 localhost kernel: IP: [<f7e9a3c7>] era_destroy+0x7/0x60 [dm_era]
Sep 24 22:44:22 localhost kernel: *pdpt =3D 0000000001945001 *pde =3D 00000003ff97f067
Sep 24 22:44:22 localhost kernel: Oops: 0000 [#1] SMP
Sep 24 22:44:22 localhost kernel: last sysfs file: /sys/module/dm_mod/initstate

Thanks
Romu
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