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
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.
make ovbd-loop
Or just
make
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>
This is another example, driven in device-mapper framework, take a device which is filled by LSMT-File blobs.
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).
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>
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`/6GOOD LUCK !