From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heinz Mauelshagen Subject: Re: RHEL6.6 dm-cache and dm-era Date: Thu, 25 Sep 2014 12:19:55 +0200 Message-ID: <5423EC4B.5070904@redhat.com> References: <54164DC0.3020907@gmail.com> <541A977D.7010108@gmail.com> <6FC8490A-55CA-454E-83FE-061A33FDE8DE@redhat.com> <5423B1E0.4000400@gmail.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1311280840224902943==" Return-path: In-Reply-To: <5423B1E0.4000400@gmail.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: device-mapper development List-Id: dm-devel.ids This is a multi-part message in MIME format. --===============1311280840224902943== Content-Type: multipart/alternative; boundary="------------080403030002090902040704" This is a multi-part message in MIME format. --------------080403030002090902040704 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit On 09/25/2014 08:10 AM, Romu Hu wrote: > 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? No calculation: it's the size of your era target in sectors. Typically "blockdev --getsz origin_dev" > 2) Any documentation for dmsetup tables? Look for examples in the kernel source trees Documentaion/device.mapper. table line syntax is: "start_sector length_in_sectors " > 3) Both my metadata_dev and origin_dev are 10G partitions, is this all > right? Metadata device size is plenty but that depends on how many eras with how many updates you want to have. > 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? You may use 4096 = _8_ sectors, you used 4096 sectors = 2MB below. It's the granularity the era target housekeeps blocks for. > > I tried the following command: > > # dmsetup create MyEra --table "0 160000 era /dev/mapper/mpathap1 > /dev/mapper/mpathbp1 4096" May not be same physical device for data and metadata! If it is, thta'd explain your oops. # dmsetup create MyEra --table "0 $(blockdev --getsz /dev/mapper/mpathbp) era whatever_disctinct_metadata_device /dev/mapper/mpathbp1 8" Would use 8 sector block size (which is tiny!) with disctinct metadata and data devices (presumabyl your ext4 sits on /dev/mapper/mpathbp1) Heinz > > 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 > > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel --------------080403030002090902040704 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable X-MIME-Autoconverted: from 8bit to quoted-printable by mx5-phx2.redhat.com id s8PAJxUT020454 On 09/25/2014 08:10 AM, Romu Hu wrote:
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 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. =A0However, it does appear that you are perhaps specifying the wrong devices when creating the era device? =A0Looks like you might be allowing th= e 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?

=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/Documentation/device-mapper/era.txt= , I guess it should be (4 * nr_blocks) bytes + buffers, but what is nr_blocks and what is buffers?

No calculation: it's the size of your era target in sectors. Typically "blockdev --getsz origin_dev"

2) Any documentation for dmsetup tables?

Look for examples in the kernel source trees Documentaion/device.mapper.

table line syntax is: "start_sector length_in_sectors <target> <target_arguments{0,N}>"

3) Both my metadata_dev and origin_dev are 10G partitions, is this all right?

Metadata device size is plenty but that depends on how many eras with how many updates you want to have.

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?

You may use 4096 =3D _8_ sectors, you used 4096 sectors =3D 2MB below= .
It's the granularity the era target housekeeps blocks for.

I tried the following command:

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

May not be=A0 same physical device for data and metadata!
If it is, thta'd explain your oops.

# dmsetup create MyEra --table "0 $(blockdev --getsz /dev/mapper/mpathbp) era whatever_disctinct_metadata_device /dev/mapper/mpathbp1 8"=

Would use 8 sector block size (which is tiny!) with disctinct metadata and data devices (presumabyl your ext4 sits on /dev/mapp= er/mpathbp1)

Heinz


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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