On Mon, Aug 01, 2022 at 12:18:53PM +1000, Alistair Popple wrote: > > AFAICT there is no reason to 'continue' in most of these paths since > > we intend to return to userspace with an error anyhow? Why try to > > isolate more pages? > > The main reason would be if callers want to retry the operation. AFAIK > isolate_folio_lru() can have transient failures, so if callers want to > retry it makes sense to isolate and migrate as many pages as possible > rather than one page at a time as subsequent retries may find different > pages that can't be isolated. Except we don't try to do the migrate, we just isolate and then unisolate and return failure. > Actually I should have called this out more clearly - the previous > behaviour on isolation failure was to retry indefinitely which is what > lead to looping in the kernel. This patch turns isolation failure into > an error and doesn't retry. I wonder though if we need to maintain a > retry count similar to what migrate_pages() does if there are unexpected > page refs? This makes more sense, exporting this mess to the caller and hoping they retry (they won't) doesn't make sense.. Jason
