sharpe at example
Jul 6, 2000, 9:01 AM
Post #1 of 1
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Modifying drbd.c and drbdsetup.c to allow retrieving device config
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Hi,
I am starting to use drbd, and noticed that there was no command to
retrieve the current config of a device.
I had in mind doing something like:
drbdsetup /dev/nb0
and getting the following listed:
Device Lower-device My Addr Remote Addr Other info
/dev/nb0 /dev/hda3 some.node.com node2.node.com xxx xxx xxx
The first thing I tried was adding an IOCTL that allowed me to GET_CONFIG,
and this all works. It was such a small piece of code, and I managed to not
crash my kernel.
However, I found that the lower-device that gets returned is the file
descriptor that drbdsetup got when opening the lower device to check that
it exists before doing the SET_CONFIG IOCTL. This is not very useful.
So, I figured that I need to change drbd.c some more, and then decided that
I better make suggestions here and ask question.
What I think I want to get back is the device number, i_dev which is
available in the inode for the device special file and which drdb stashes
away.
At first, I though of overwriting lower_device in drbd_conf[minor].conf
with inode->i_dev, but this seems wrong, as the info passed in changes when
the config is retrieved.
So, it seems to me that we need to change the meaning of lower_device in
the config that is passed in via the SET_CONFIG IOCTL. It should be a dev_t.
However, this means changes in drbd.c and drbdsetup.c ...
My next problem is, even if I retrieve the device id, and split it into a
major and minor device number, how do I translate that back into
/dev/[hs]d[a-z][0-9] etc?
I think I can open /proc/devices and rummage through it looking for the
name of the major device, and then look in /dev for the device with that
minor number.
Is there a better way to translate back from major, minor to a device
special file?
Regards
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Richard Sharpe, sharpe [at] example
Samba (Team member, www.samba.org), Ethereal (Team member, www.zing.org)
Co-author, SAMS Teach Yourself Samba in 24 Hours
Author: First Australian 5-day, intensive, hands-on Linux SysAdmin course
Author: First Australian 2-day, intensive, hands-on Samba course
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