Messages in this thread | | | Date | Thu, 9 Dec 2021 19:26:19 +0800 | Subject | Re: [PATCH v1 1/2] virtio-mem: prepare page onlining code for granularity smaller than MAX_ORDER - 1 | From | Eric Ren <> |
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Hi David,
Thanks for working on this!
On 2021/11/26 21:42, David Hildenbrand wrote: > Let's prepare our page onlining code for subblock size smaller than > MAX_ORDER - 1: we'll get called for a MAX_ORDER - 1 page but might have > some subblocks in the range plugged and some unplugged. In that case, > fallback to subblock granularity to properly only expose the plugged > parts to the buddy. > > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > drivers/virtio/virtio_mem.c | 86 ++++++++++++++++++++++++++----------- > 1 file changed, 62 insertions(+), 24 deletions(-) > > diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c > index 96e5a8782769..03e1c5743699 100644 > --- a/drivers/virtio/virtio_mem.c > +++ b/drivers/virtio/virtio_mem.c > @@ -20,6 +20,7 @@ > #include <linux/mutex.h> > #include <linux/bitmap.h> > #include <linux/lockdep.h> > +#include <linux/log2.h> > > #include <acpi/acpi_numa.h> > > @@ -1228,28 +1229,46 @@ static void virtio_mem_fake_offline_cancel_offline(unsigned long pfn, > page_ref_inc(pfn_to_page(pfn + i)); > } > > -static void virtio_mem_online_page_cb(struct page *page, unsigned int order) > +static void virtio_mem_online_page(struct virtio_mem *vm, > + struct page *page, unsigned int order) > { > - const unsigned long addr = page_to_phys(page); > - unsigned long id, sb_id; > - struct virtio_mem *vm; > + const unsigned long start = page_to_phys(page); > + const unsigned long end = start + PFN_PHYS(1 << order); > + unsigned long addr, next, id, sb_id, count; > bool do_online; > > - rcu_read_lock(); > - list_for_each_entry_rcu(vm, &virtio_mem_devices, next) { > - if (!virtio_mem_contains_range(vm, addr, PFN_PHYS(1 << order))) > - continue; > + /* > + * We can get called with any order up to MAX_ORDER - 1. If our > + * subblock size is smaller than that and we have a mixture of plugged > + * and unplugged subblocks within such a page, we have to process in > + * smaller granularity. In that case we'll adjust the order exactly once > + * within the loop. > + */ > + for (addr = start; addr < end; ) { > + next = addr + PFN_PHYS(1 << order); > > if (vm->in_sbm) { > - /* > - * We exploit here that subblocks have at least > - * MAX_ORDER_NR_PAGES size/alignment - so we cannot > - * cross subblocks within one call. > - */ > id = virtio_mem_phys_to_mb_id(addr); > sb_id = virtio_mem_phys_to_sb_id(vm, addr); > - do_online = virtio_mem_sbm_test_sb_plugged(vm, id, > - sb_id, 1); > + count = virtio_mem_phys_to_sb_id(vm, next - 1) - sb_id + 1; > + > + if (virtio_mem_sbm_test_sb_plugged(vm, id, sb_id, count)) { > + /* Fully plugged. */ > + do_online = true; > + } else if (count == 1 || > + virtio_mem_sbm_test_sb_unplugged(vm, id, sb_id, count)) { > + /* Fully unplugged. */ > + do_online = false; > + } else { > + /* > + * Mixture, process sub-blocks instead. This > + * will be at least the size of a pageblock. > + * We'll run into this case exactly once. > + */ > + order = ilog2(vm->sbm.sb_size) - PAGE_SHIFT; > + do_online = virtio_mem_sbm_test_sb_plugged(vm, id, sb_id, 1); > + continue; > + } > } else { > /* > * If the whole block is marked fake offline, keep > @@ -1260,18 +1279,38 @@ static void virtio_mem_online_page_cb(struct page *page, unsigned int order) > VIRTIO_MEM_BBM_BB_FAKE_OFFLINE; > } > > + if (do_online) > + generic_online_page(pfn_to_page(PFN_DOWN(addr)), order); > + else > + virtio_mem_set_fake_offline(PFN_DOWN(addr), 1 << order, > + false); Should we just use PHYS_PFN() here? addr is obviously PFN aligned. Anyway, it doesn't matter.
LGTM. Reviewed-by: Eric Ren <renzhengeek@gmail.com> > + addr = next; > + } > +} > + > +static void virtio_mem_online_page_cb(struct page *page, unsigned int order) > +{ > + const unsigned long addr = page_to_phys(page); > + struct virtio_mem *vm; > + > + rcu_read_lock(); > + list_for_each_entry_rcu(vm, &virtio_mem_devices, next) { > /* > - * virtio_mem_set_fake_offline() might sleep, we don't need > - * the device anymore. See virtio_mem_remove() how races > + * Pages we're onlining will never cross memory blocks and, > + * therefore, not virtio-mem devices. > + */ > + if (!virtio_mem_contains_range(vm, addr, PFN_PHYS(1 << order))) > + continue; > + > + /* > + * virtio_mem_set_fake_offline() might sleep. We can safely > + * drop the RCU lock at this point because the device > + * cannot go away. See virtio_mem_remove() how races > * between memory onlining and device removal are handled. > */ > rcu_read_unlock(); > > - if (do_online) > - generic_online_page(page, order); > - else > - virtio_mem_set_fake_offline(PFN_DOWN(addr), 1 << order, > - false); > + virtio_mem_online_page(vm, page, order); > return; > } > rcu_read_unlock(); > @@ -2438,8 +2477,7 @@ static int virtio_mem_init_hotplug(struct virtio_mem *vm) > /* > * We want subblocks to span at least MAX_ORDER_NR_PAGES and > * pageblock_nr_pages pages. This: > - * - Simplifies our page onlining code (virtio_mem_online_page_cb) > - * and fake page onlining code (virtio_mem_fake_online). > + * - Simplifies our fake page onlining code (virtio_mem_fake_online). > * - Is required for now for alloc_contig_range() to work reliably - > * it doesn't properly handle smaller granularity on ZONE_NORMAL. > */
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