On 24/04/18 18:17, Sinan Kaya wrote: > On 4/24/2018 5:33 AM, Jean-Philippe Brucker wrote: >>> Please return pasid when you find an io_mm that is already bound. Something like >>> *pasid = io_mm->pasid should do the work here when bond is true. >> Right. I think we should also keep returning 0, not switch to -EEXIST or >> similar. So in next version a driver can call bind(devX, mmY) multiple >> times, but the first unbind() removes the bond. > > If we are going to allow multiple binds, then the last unbind should > remove the bond rather than the first one via reference counting. Yeah that's probably better. Since a bond belongs to a device driver it doesn't need multiple bind/unbind, so earlier in this thread (1/37) I talked about removing the bond->refs. But thinking about it, there still is a need for it. When mm exits, we now need to call the device driver's mm_exit handler outside of the spinlock, so we have to take a ref in order to prevent a concurrent unbind() from freeing the bond. Thanks, Jean
