On Fri, Nov 08, 2024 at 01:42:15PM -0800, Joanne Koong wrote: > On Fri, Nov 8, 2024 at 1:27 PM Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote: > > > > On Fri, Nov 08, 2024 at 08:00:25PM +0100, David Hildenbrand wrote: > > > On 08.11.24 19:56, David Hildenbrand wrote: > > > > On 08.11.24 18:33, SeongJae Park wrote: > > > > > + David Hildenbrand > > > > > > > > > > On Thu, 7 Nov 2024 15:56:12 -0800 Joanne Koong <joannelkoong@xxxxxxxxx> wrote: > > > > > > > > > > > In offline_pages(), do_migrate_range() may potentially retry forever if > > > > > > the migration fails. Add a return value for do_migrate_range(), and > > > > > > allow offline_page() to try migrating pages 5 times before erroring > > > > > > out, similar to how migration failures in __alloc_contig_migrate_range() > > > > > > is handled. > > > > > > > > > > I'm curious if this could cause unexpected behavioral differences to memory > > > > > hotplugging users, and how '5' is chosen. Could you please enlighten me? > > > > > > > > > > > > > I'm wondering how much more often I'll have to nack such a patch. :) > > > > > > A more recent discussion: https://lore.kernel.org/linux-mm/52161997-15aa-4093-a573-3bfd8da14ff1@xxxxxxxxxxx/T/#mdda39b2956a11c46f8da8796f9612ac007edbdab > > > > > > Long story short: this is expected and documented > > > > Thanks David for the background. > > > > Joanne, simply drop this patch. It is not required for your series. > > Awesome, I'm happy to drop this patch. > > Just curious though - don't we need this in order to mitigate the > scenario where if an unprivileged fuse server never completes > writeback, we don't run into this infinite loop? Or is it that memory > hotplugging is always initiated from userspace so if it does run into > an infinite loop (like also in that thread David linked), userspace is > responsible for sending a signal to terminate it? I think irrespective of the source of the hotplug, the current behavior of infinite retries in some cases is documented and kind of expected, so no need to fix it. (Though I don't know all the source of hotplug.)
