| |
|
 |
|
 |
|
|
|
| |
|
|
xen-devel
[Xen-devel] Re: xl create should refuse to share block devices RW betwee
On 07/27/2010 08:17 AM, Ian Jackson wrote:
Jeremy Fitzhardinge writes ("xl create should refuse to share block devices RW
between domains"):
When creating a domain, "xl create" should fail if a block device is
shared RW between domains, like xm create does.
I'm not sure how this would be implemented. Search xenstore for
references to the device when setting up a domain?
Does this safety catch have to be 100% reliable ? If not then there
are some useful heuristics: for example, you could see whether the
device is a devmapper device and if so check its open count. That
would catch simultaneously mounting the fs in dom0.
Well, my specific use case is that I have pairs of domain configs, one
PV, one HVM, referring to the same set of resources. I want xl create
to catch when I try and create the PV version of a domain while the HVM
is still running.
A more comprehensive check would be nice, but just this would be
useful. But whatever it does check should be 100% reliable.
Doesn't the kernel already have some features to try to stop multiple
conflicting uses of the same block device ? Perhaps blktap[2] should
do the same ?
Not in general. The only interlock the kernel has is that you can't
change the partition mapping on a device while it is in use. The
e2fsprogs do generally try to stop mistakes like fscking a mounted
filesystem, but it fails to detect if the block device is being used by
blktap (and that does make quite a bit of a mess, it turns out...).
J
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
| |
|
Home