Re: [PATCH] modules: load modules from versioned /var/run dir

[Michael Tokarev]

10.03.2020 12:39, Stefan Hajnoczi wrote:
> On Fri, Mar 06, 2020 at 02:26:48PM +0100, Christian Ehrhardt wrote:
>> On upgrades the old .so files usually are replaced. But on the other
>> hand since a qemu process represents a guest instance it is usually kept
>> around.
>>
>> That makes late addition of dynamic features e.g. 'hot-attach of a ceph
>> disk' fail by trying to load a new version of e.f. block-rbd.so into an
>> old still running qemu binary.
>>
>> This adds a fallback to also load modules from a versioned directory in the
>> temporary /var/run path. That way qemu is providing a way for packaging
>> to store modules of an upgraded qemu package as needed until the next reboot.
>>
>> An example how that can then be used in packaging can be seen in:
>> https://git.launchpad.net/~paelzer/ubuntu/+source/qemu/log/?h=bug-1847361-miss-old-so-on-upgrade-UBUNTU
>>
>> Fixes: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1847361
>> Signed-off-by: Christian Ehrhardt <address@hidden>
>> ---
>>  util/module.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
> 
> CCing Debian, Fedora, and Red Hat package maintainers in case they have
> comments.
> 
> The use of /var/run makes me a little uneasy.  I guess it's related to
> wanting to uninstall the old package so the .so in their original
> location cannot be used (even if they had a versioned path)?

BTW, this is /run nowadays, not /var/run, as far as I can see.

/mjt