[PATCH v6 20/21] PCI/P2PDMA: Introduce pci_mmap_p2pmem()

[Jason Gunthorpe]

On Thu, Jun 02, 2022 at 10:16:10AM -0600, Logan Gunthorpe wrote:

> > Just stuff the pages into the mmap, and your driver unprobe will
> > automatically block until all the mmaps are closed - no different than
> > having an open file descriptor or something.
> 
> Oh is that what we want?

Yes, it is the typical case - eg if you have a sysfs file open unbind
hangs indefinitely. Many drivers can't unbind while they have open file
descriptors/etc.

A couple drivers go out of their way to allow unbinding while a live
userspace exists but this can get complicated. Usually there should be
a good reason.

The module will already be refcounted anyhow because the mmap points
to a char file which holds a module reference - meaning a simple rmmod
of the driver shouldn't work already..

Jason