On Mon, Jun 19, 2023 at 02:51:21PM +0800, Wupeng Ma wrote: > From: David Hildenbrand <david@xxxxxxxxxx> > > commit 8dc4bb58a146655eb057247d7c9d19e73928715b upstream. > > virtio-mem soon wants to use offline_and_remove_memory() memory that > exceeds a single Linux memory block (memory_block_size_bytes()). Let's > remove that restriction. > > Let's remember the old state and try to restore that if anything goes > wrong. While re-onlining can, in general, fail, it's highly unlikely to > happen (usually only when a notifier fails to allocate memory, and these > are rather rare). > > This will be used by virtio-mem to offline+remove memory ranges that are > bigger than a single memory block - for example, with a device block > size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory > block size of 128MB. > > While we could compress the state into 2 bit, using 8 bit is much > easier. > > This handling is similar, but different to acpi_scan_try_to_offline(): > > a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG > optimization is still relevant - it should only apply to ZONE_NORMAL > (where we have no guarantees). If relevant, we can always add it. > > b) acpi_scan_try_to_offline() simply onlines all memory in case > something goes wrong. It doesn't restore previous online type. Let's do > that, so we won't overwrite what e.g., user space configured. > > Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> > Cc: Jason Wang <jasowang@xxxxxxxxxx> > Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Oscar Salvador <osalvador@xxxxxxx> > Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > Link: https://lore.kernel.org/r/20201112133815.13332-28-david@xxxxxxxxxx > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> > --- > mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++------- > 1 file changed, 89 insertions(+), 16 deletions(-) > Why is this needed in 5.10.y? Looks like a new feature to me, what problem does it solve there? thanks, greg k-h
