On Fri, Dec 11, 2020 at 10:53:00PM +0100, David Hildenbrand wrote: > > When check_and_migrate_movable_pages() is called, the pages are > > already pinned. If some of those pages are in movable zone, and we > > fail to migrate or isolate them what should we do: proceed, and > > keep it as exception of when movable zone can actually have pinned > > pages or unpin all pages in the array, and return an error, or > > unpin only pages in movable zone, and return an error? > > I guess revert what we did (unpin) and return an error. The > interesting question is what can make migration/isolation fail > > a) out of memory: smells like a zone setup issue. Failures are acceptable I guess. Out of memory is reasonable.. > b) short term pinnings: process dying - not relevant I guess. Other cases? (Fork?) Concurrent with non-longterm GUP users are less reasonable, fork is not reasonable, etc.. Racing with another GUP in another thread is also not reasonable, so failing to isolate can't be a failure Jasnon
