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<div class="moz-cite-prefix">On 09/29/2014 04:31 AM, Romu Hu wrote:<br>
</div>
<blockquote cite="mid:5428C46C.9050908@gmail.com" type="cite">
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On 2014/9/26 18:33, Heinz Mauelshagen wrote:<br>
<blockquote cite="mid:54254116.5090908@redhat.com" type="cite">
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<br>
Romu,<br>
<br>
did you initialize the metadata device before trying to create
the era target?<br>
Zeroes in the first KBs will do.<br>
</blockquote>
<br>
Thanks Heinz, it solved the problem. Is it the proper way to
initialize the metadata device of an era target or just a
workaround?<br>
</blockquote>
<br>
It is the proper way to address it when using dmsetup.<br>
<br>
MInd you dmsetup is a low-level tool which is very handy for
testing/evatuation<br>
like in your use case.<br>
<br>
Ultimately dm-era will be supported by lvm and eventually other
higher level tools,<br>
which will be in charge of doing metadata device initialization.<br>
<br>
Heinz<br>
<br>
<blockquote cite="mid:5428C46C.9050908@gmail.com" type="cite"> <br>
Thanks<br>
Romu<br>
<br>
<blockquote cite="mid:54254116.5090908@redhat.com" type="cite">
Yes, check for NULL in era_destroy is needed to handle the
error path you hit properly.<br>
<br>
Heinz<br>
<br>
<div class="moz-cite-prefix">On 09/26/2014 05:16 AM, Romu Hu
wrote:<br>
</div>
<blockquote cite="mid:5424DA99.2070308@gmail.com" type="cite">
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On 2014/9/25 22:57, Heinz Mauelshagen wrote:<br>
<blockquote cite="mid:54242D6D.4090004@redhat.com" type="cite">
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Romu,<br>
<br>
"dmsetup create MyEra --table "0 20971520
/dev/mapper/mpathbp1 /dev/mapper/mpathap1 8"<br>
<br>
should read<br>
<br>
dmsetup create MyEra --table "0 20971520 era
/dev/mapper/mpathbp1 /dev/mapper/mpathap1 8"<br>
</blockquote>
<br>
Sorry my bad.<br>
<br>
I ran 'dmsetup create MyEra --table "0 20971520 era
/dev/mapper/mpathbp1 /dev/mapper/mpathap1 8"' but kernel
(2.6.32-494.el6.i686) oopsed:<br>
<br>
<tt>Sep 25 18:34:11 localhost kernel: device-mapper: era:
sb_check failed: magic 0: wanted 2126579579</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: device-mapper:
block manager: superblock validator check failed for block 0</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: device-mapper: era:
couldn't read_lock superblock</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: BUG: unable to
handle kernel NULL pointer dereference at 00000008</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: IP:
[<f7e2b3c7>] era_destroy+0x7/0x60 [dm_era]Sep 25
18:34:11 localhost kernel: *pdpt = 0000000032457001 *pde =
00000003fb5fa067</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: Oops: 0000 [#1] SMP</tt><tt><br>
</tt><tt>Sep 25 18:34:11 localhost kernel: last sysfs file:
/sys/module/dm_persistent_data/initstate</tt><br>
<br>
Perhaps this should be cherry-picked?<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=989f26f5ad308f40a95f280bf9cd75e558d4f18d">https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=989f26f5ad308f40a95f280bf9cd75e558d4f18d</a><br>
<br>
The log says sb_check failed, anything wrong with the dmsetup
command parameters?<br>
<br>
Thanks<br>
Romu<br>
<br>
<blockquote cite="mid:54242D6D.4090004@redhat.com" type="cite">
<div class="moz-cite-prefix">On 09/25/2014 04:02 PM, Romu
wrote:<br>
</div>
<blockquote
cite="mid:CANoG8sWXjR5LmZvY2K1ebOr=kS+A=-EPveqh=XsqD0v6bWcc2g@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">2014-09-25 18:19 GMT+08:00
Heinz Mauelshagen <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:heinzm@redhat.com" target="_blank">heinzm@redhat.com</a>></span>:<br>
<blockquote class="gmail_quote" style="margin:0px
0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"><span
class=""> On 09/25/2014 08:10 AM, Romu Hu
wrote:<br>
<blockquote type="cite"> On 2014/9/24 12:10,
Brassow Jonathan wrote:<br>
<blockquote type="cite">On Sep 22, 2014, at
7:35 AM, Romu wrote:
<div><br>
<blockquote type="cite"><span
style="border-collapse:separate;font-family:Helvetica;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:-webkit-auto;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;font-size:medium">I
tried the following command to set
up my era target but the command
immediately panics the system and
the system reboots.
<div><br>
</div>
<div># dmsetup create MyEra --table
"0 41941903 era
/dev/mapper/VG-CacheDataLV_cmeta
/dev/mapper/VG-OriginLV 4096"<br>
</div>
<div><br>
</div>
<div>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.<br>
</div>
<div><br>
</div>
<div>Below is the message in
/var/log/messages after running
the dmsetup comnmand:</div>
<div><br>
</div>
<div>kernel: device-mapper: era:
sb_check failed: magic 1623043:
wanted <a moz-do-not-send="true"
href="tel:2126579579"
value="+12126579579"
target="_blank">2126579579</a><br>
</div>
<div>
<div>kernel: device-mapper: block
manager: superblock validator
check failed for block 0</div>
<div>kernel: device-mapper: era:
couldn't read_lock superblock</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Any idea?</div>
</span><br>
</blockquote>
</div>
<br>
<div>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?</div>
<div><br>
</div>
<div> brassow</div>
</blockquote>
<br>
I think the dmsetup command to set up an era
target should be something like this:<br>
<br>
<tt><span
style="border-collapse:separate;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;font-size:medium">#
dmsetup create MyEra --table "0
sector_number era metadeta_dev
origin_dev block_size"</span></tt><br>
<br>
My questions:<br>
<br>
1) How to calculate sector_number?
According to <a moz-do-not-send="true"
href="https://www.kernel.org/doc/Documentation/device-mapper/era.txt"
target="_blank">https://www.kernel.org/doc/Documentation/device-mapper/era.txt</a>,
I guess it should be (4 * nr_blocks) bytes +
buffers, but what is nr_blocks and what is
buffers?<br>
</blockquote>
<br>
</span> No calculation: it's the size of your
era target in sectors. Typically "blockdev
--getsz origin_dev"<span class=""><br>
<br>
<blockquote type="cite"> 2) Any documentation
for dmsetup tables?<br>
</blockquote>
<br>
</span> Look for examples in the kernel source
trees Documentaion/device.mapper.<br>
<br>
table line syntax is: "start_sector
length_in_sectors <target>
<target_arguments{0,N}>"<span class=""><br>
<br>
<blockquote type="cite"> 3) Both my
metadata_dev and origin_dev are 10G
partitions, is this all right?<br>
</blockquote>
<br>
</span> Metadata device size is plenty but that
depends on how many eras with how many updates
you want to have.<span class=""><br>
<br>
<blockquote type="cite"> 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?<br>
</blockquote>
<br>
</span> You may use 4096 = _8_ sectors, you used
4096 sectors = 2MB below.<br>
It's the granularity the era target housekeeps
blocks for.<span class=""><br>
<br>
<blockquote type="cite"> <br>
I tried the following command:<br>
<br>
<tt># dmsetup create MyEra --table "0 160000
era /dev/mapper/mpathap1
/dev/mapper/mpathbp1 4096"</tt><br>
</blockquote>
<br>
</span> May not be same physical device for
data and metadata!<br>
If it is, thta'd explain your oops.<br>
<br>
<tt># dmsetup create MyEra --table "0 $(blockdev
--getsz </tt><tt><tt>/dev/mapper/mpathbp)</tt>
era whatever_disctinct_metadata_device
/dev/mapper/mpathbp1 8"</tt><br>
<br>
Would use 8 sector block size (which is tiny!)
with disctinct metadata and data devices
(presumabyl your ext4 sits on <tt>/dev/mapper/mpathbp1)</tt><span
class=""><font color="#888888"><br>
<br>
Heinz<br>
</font></span></div>
</blockquote>
<div><br>
</div>
<div>Heinz, thank you for your help!</div>
<div><br>
</div>
<div>My origin dev is 10G so total sector number
is 20971520. /dev/mapper/mpathbp1 (/dev/dm-6) is
the metadata dev, /dev/mapper/mpathap1 (/dev/dm-7)
is the origin dev, they are on different LUNs.</div>
<div><br>
</div>
<div>I tried the following commands:</div>
<div><br>
</div>
<div># dmsetup create MyEra --table "0 20971520
/dev/mapper/mpathbp1 /dev/mapper/mpathap1 8"<br>
</div>
<div># Target type name /dev/mapper/mpathbp1 is too
long.</div>
<div>
<div># Command failed</div>
</div>
<div><br>
</div>
<div># dmsetup create MyEra --table "0 20971520
/dev/dm-6 /dev/dm-7 8"<br>
</div>
<div># device-mapper: reload ioctl on MyEra failed:
Invalid argument</div>
<div>
<div># Command failed</div>
</div>
<div><br>
</div>
<div>And when executing the second command I see the
following in /var/log/messages:</div>
<div><br>
</div>
<div>
<div>Sep 25 06:37:48 localhost kernel:
device-mapper: table: 253:8: /dev/dm-6: unknown
target type</div>
<div>Sep 25 06:37:48 localhost kernel:
device-mapper: ioctl: error adding target to
table</div>
<div>Sep 25 06:37:48 localhost multipathd: dm-8:
remove map (uevent)</div>
<div>Sep 25 06:37:48 localhost multipathd: dm-8:
devmap not registered, can't remove</div>
<div>Sep 25 06:37:48 localhost multipathd: dm-8:
remove map (uevent)</div>
<div>Sep 25 06:37:48 localhost multipathd: dm-8:
devmap not registered, can't remove</div>
</div>
<div><br>
</div>
<div>Then I run 'mkfs.ext4 /dev/dm-6' and tried the
second command again but got the same result.</div>
<div><br>
</div>
<div>Any idea?</div>
<div><br>
</div>
<div>Thanks</div>
<div>Romu</div>
</div>
</div>
</div>
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===============================================================
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