Re: Not able to create a device mapper target node

[Zdenek Kabelac <zkabelac@redhat.com>]

Dne 24.6.2013 09:19, monica g napsal(a):
> Hi,
>
> I wrote a basic device mapper driver which caches reads.
>
> I gave dm msg prefix as below
>   #define DM_MSG_PREFIX "cacheread".
>
> When i try to create a device mapper node using the below command
> echo "0 `blockdev --getsize /dev/sda2` cacheread /dev/sda2 0" | dmsetup create
> cacheread
>
> the system hangs.I am not getting any error messages.

Why not looking into a basic linear driver -

linux/drivers/md/dm-stripe.c

and start updating this driver for your needs.
Kernel device driver development is not easily debugable from userspace.

Also you might be interested to look at  dm-cache driver available from 3.9
kernel and which does much more advanced caching of reads as well as writes....

Regards

Zdenek


>
> When i try to create a device mapper node for linear target(this target is
> already present with the device mapper code) using below command
>
> echo "0 `blockdev --getsize /dev/sda2` linear /dev/sda2 0" | dmsetup create linear
> it succeeds and creates device node linear in /dev/mapper directory.
>
> I am stuck with this issue and not able to proceed furthur.
>
> Please let me know if you have any suggestions.
>
> Any help is truely appreciated.
>
> Thanks in advance.
>
> Regards,
> Monica
>
>
>
>
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