On Sat, Dec 08, 2018 at 10:26:04AM -0800, Christoph Hellwig wrote: > On Sat, Dec 08, 2018 at 12:47:30PM -0500, Jerome Glisse wrote: > > Most of the user of GUP are well behave (everything under driver/gpu and > > so is mellanox driver and many other) ie they abide by mmu notifier > > invalidation call backs. They are a handfull of device driver that thought > > they could just do GUP and ignore the mmu notifier part and those are the > > one being problematic. So to me it feels like bystander are be shot for no > > good reasons. > > get_user_pages is used by every single direct I/O, and while the race > windows in that case are small they very much exists. Yes and my proposal allow to fix that in even a better way than the pin count would ie allowing to provide a callback for write back to wait on direct I/O as you said for direct I/O it is a small window so it would be fine to have write back wait on it. Cheers, Jérôme
