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dadi-kernel-mod

dadi overlay-bd device driver / device-mapper

Usage,

make [KDOOT=linux_kernel_dir] [ovbd-loop|ovbd-dm]

KROOT set as kernel module develop kit path, ignored to use host kernel build environment

ovbd-loop (deprecated)

This is a basic sample for dadi overlay-bd image block-device driver, currently implemented just like loop-device in kernel, reading image file via vfs to feed bio read requests.

Build

make ovbd-loop

Or just

make

Use

The image file should be LSMT-File on ZFile(without Tar file header currently.), image path can be configured by parameter.

insmod ./vbd.ko backfile=<absolute path0>,<absolute path1>,<absolute path2>...

if succeed, a read-only device called /dev/vbd0 should appeared,

mount /dev/vdb0 <mount point>

ovbd-dm

This is another example, driven in device-mapper framework, take a device which is filled by LSMT-File blobs.

Build

To build it, using make ovbd-dm

To use it, currently should know the image block-device size. (Which should be read by LSMT-File tailer, but the cli tools are not ready by now).

Use

First of all, install the module

insmod vbd.ko

It can be simply get ready by loop device:

losetup -f --show -r --direct-io <LSMTFile absolute path>

Say the loop device is /dev/loop0 for example. Now able to create mapped device using dmsetup

dmsetup create --concise "zfile0,,,ro,0 <zfile unzip size> zfile_target /dev/loop0 <lsmt actual size>"

dmsetup create --concise "lsmt0,,,ro,0 2290872 lsmt_target /dev/zfile0 <lsmt actual size>"

Here the vbd0 is device name for mapped-device (as /dev/mapper/vbd0), set ro flag to make sure device is read-only. In table part, there are tow target types zfile_target and lsmt_target, then follows underlay lsmt format block parameter, path and length in bytes. (Currently supports only one layer). then the list of image devices.

After the mapped-device ready, it could able to mount

mount /dev/mapper/vbd0 <mount point>

Test Image

We upload test image to https://dadi-shared.oss-cn-beijing.aliyuncs.com/kernel-test/obd_testimg.tgz.

Start test with the commands:

wget https://dadi-shared.oss-cn-beijing.aliyuncs.com/kernel-test/obd_testimg.tgz
tar -zxvf obd_testimg.tgz
cd obd_testimg/
cp /path/to/vbd.ko ./
insmod ./vbd.ko backfile=`pwd`/0,`pwd`/1,`pwd`/2,`pwd`/3,`pwd`/4,`pwd`/5,`pwd`/6

GOOD LUCK !

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DADI OverlayBD simple implementation as a kernel module.

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