block mapping

block mapping

[Kasatkin, Dmitry]

Hello All,

I would like to implement such block device, which can store
additional information along with the block data.
For example. so if file system has 4k block, I would like to store
4k+256b of additional information...

Can such block device be implemented with device mapper?

Thank you,

Dmitry

Re: block mapping

[Zdenek Kabelac]

Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a):
> Hello All,
> 
> I would like to implement such block device, which can store
> additional information along with the block data.
> For example. so if file system has 4k block, I would like to store
> 4k+256b of additional information...
> 
> Can such block device be implemented with device mapper?
> 

Yes - i.e.the old snapshot target stores the block and it's remapping info
(thought the size info is much smaller then 256b)

Zdenek

Re: block mapping

[Christoph Hellwig]

On Thu, Sep 29, 2011 at 04:35:44PM +0300, Kasatkin, Dmitry wrote:
> Hello All,
> 
> I would like to implement such block device, which can store
> additional information along with the block data.
> For example. so if file system has 4k block, I would like to store
> 4k+256b of additional information...
> 
> Can such block device be implemented with device mapper?

Given your other recent posts you probably want to take a look at
dm-verity:

	http://selinuxproject.org/~jmorris/lss2011_slides/LSS_11_Integrity_checked_block_devices.pdf

(even if that's not strictly what you are asking for here)

Re: block mapping

[Kasatkin, Dmitry]

On Thu, Sep 29, 2011 at 4:55 PM, Christoph Hellwig <hch@infradead.org> wrote:
> On Thu, Sep 29, 2011 at 04:35:44PM +0300, Kasatkin, Dmitry wrote:
>> Hello All,
>>
>> I would like to implement such block device, which can store
>> additional information along with the block data.
>> For example. so if file system has 4k block, I would like to store
>> 4k+256b of additional information...
>>
>> Can such block device be implemented with device mapper?
>
> Given your other recent posts you probably want to take a look at
> dm-verity:
>
>        http://selinuxproject.org/~jmorris/lss2011_slides/LSS_11_Integrity_checked_block_devices.pdf
>

Yes... I know this..
That target stores integrity data on a separate block device.
I am looking to possibility to store data with the block...

Thanks
> (even if that's not strictly what you are asking for here)
>
> --
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> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>

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Re: block mapping

[Kasatkin, Dmitry]

Hello,


On Thu, Sep 29, 2011 at 4:42 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
> Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a):
>> Hello All,
>>
>> I would like to implement such block device, which can store
>> additional information along with the block data.
>> For example. so if file system has 4k block, I would like to store
>> 4k+256b of additional information...
>>
>> Can such block device be implemented with device mapper?
>>
>
> Yes - i.e.the old snapshot target stores the block and it's remapping info
> (thought the size info is much smaller then 256b)
>

1. Old snapshot target? Where is it...

2. Isn't it stores some data at the beginning of the block device - in
the header..
Like LUKS does with dm-crypt?

Thanks

> Zdenek
>
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> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
>

Re: block mapping

[Zdenek Kabelac]

Dne 29.9.2011 16:10, Kasatkin, Dmitry napsal(a):
> Hello,
> 
> 
> On Thu, Sep 29, 2011 at 4:42 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
>> Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a):
>>> Hello All,
>>>
>>> I would like to implement such block device, which can store
>>> additional information along with the block data.
>>> For example. so if file system has 4k block, I would like to store
>>> 4k+256b of additional information...
>>>
>>> Can such block device be implemented with device mapper?
>>>
>>
>> Yes - i.e.the old snapshot target stores the block and it's remapping info
>> (thought the size info is much smaller then 256b)
>>
> 
> 1. Old snapshot target? Where is it...
> 

kernel/drivers/md/dm-snap-persistent.c


> 2. Isn't it stores some data at the beginning of the block device - in
> the header..

A bit more complicated that this - but yes, quite straightforward target.


Zdenek

Re: block mapping

[Kasatkin, Dmitry]

On Thu, Sep 29, 2011 at 5:19 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
> Dne 29.9.2011 16:10, Kasatkin, Dmitry napsal(a):
>> Hello,
>>
>>
>> On Thu, Sep 29, 2011 at 4:42 PM, Zdenek Kabelac <zkabelac@redhat.com> wrote:
>>> Dne 29.9.2011 15:35, Kasatkin, Dmitry napsal(a):
>>>> Hello All,
>>>>
>>>> I would like to implement such block device, which can store
>>>> additional information along with the block data.
>>>> For example. so if file system has 4k block, I would like to store
>>>> 4k+256b of additional information...
>>>>
>>>> Can such block device be implemented with device mapper?
>>>>
>>>
>>> Yes - i.e.the old snapshot target stores the block and it's remapping info
>>> (thought the size info is much smaller then 256b)
>>>
>>
>> 1. Old snapshot target? Where is it...
>>
>
> kernel/drivers/md/dm-snap-persistent.c
>
>
>> 2. Isn't it stores some data at the beginning of the block device - in
>> the header..
>
> A bit more complicated that this - but yes, quite straightforward target.
>

Thanks

>
> Zdenek
>
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>