сб, 2 февр. 2019 г. в 03:33, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>:
>
> On Wed, Jan 30, 2019 at 04:07:30PM -0800, Pavel Shilovsky wrote:
> > Commit 28eb24ff75c5 ("cifs: Always resolve hostname before reconnecting").
> >
> > In case a hostname resolves to a different IP address (e.g. long
> > running mounts), make sure to resolve it every time prior to calling
> > generic_ip_connect() in reconnect.
> >
> > This patch needs user space changes of cifs.upcall that set a timeout
> > value for the "dns_resolver" key.
>
> Wait, you are requiring userspace to upgrade tools to support this? And
> you think that will happen to all systems running older kernels?
>
> This really feels like a new feature being added, what bug is this
> fixing that requires it to be backported to all of the stable kernel
> trees?
Let's me describe what is going to happen without upgrade of the
userspace tools. The 1st reconnect will cause proper resolving of DNS
name and storing this name into the cache. All subsequent reconnects
will use the value stored in the cache and do not attempt to resolve
this DNS name. That means the fix will help partially but doesn't
break anything.
Once the userspace tools are upgraded, the cached DNS name will expire
in 10 min, so every reconnect routine happening after that will use
new IP. So, Linux distros will fully benefit from the patch once they
upgrade the userspace tools but they do not need to synchronize
updates of the kernel and the tools.
The diff has been generated against the newest kernel but I checked
that it cherry-picks to at least 4.4.y (and probably older ones).
--
Best regards,
Pavel Shilovsky
