On Tue, 2 Aug 2022 10:30:12 +1000 Alistair Popple <apopple@xxxxxxxxxx> wrote: > When pinning pages with FOLL_LONGTERM check_and_migrate_movable_pages() > is called to migrate pages out of zones which should not contain any > longterm pinned pages. > > When migration succeeds all pages will have been unpinned so pinning > needs to be retried. This is indicated by returning zero. When all pages > are in the correct zone the number of pinned pages is returned. > > However migration can also fail, in which case pages are unpinned and > -ENOMEM is returned. However if the failure was due to not being unable > to isolate a page zero is returned. This leads to indefinite looping in > __gup_longterm_locked(). > > Fix this by simplifying the return codes such that zero indicates all > pages were successfully pinned in the correct zone while errors indicate > either pages were migrated and pinning should be retried or that > migration has failed and therefore the pinning operation should fail. > > This fixes the indefinite looping on page isolation failure by failing > the pin operation instead of retrying indefinitely. > Are we able to identify a Fixes: for this? Presumably something in the series "Add MEMORY_DEVICE_COHERENT for coherent device memory mapping"?
