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Re: [dm-devel] Not able to create a device mapper target node



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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