Michael S. Tsirkin wrote:

vhost net module wants to do copy to/from user from a kernel thread,
which needs use_mm (like what fs/aio has).  Move that into mm/ and
export to modules.

Michael, Andrew,

I am just curious: Is there any technical reason why a kthread cannot
have a long-term use_mm() in effect? (Assuming this makes sense for the
design, of course).  For the cases there we know the kthread will always
service the same context (such as with venettap/vhost, it may make sense
to do a use_mm() at init time and just leave it until the thread exits.
 Will this break anything?

Kind Regards,
-Greg