[PATCH v2 03/29] virtio-mem: simplify MAX_ORDER - 1 / pageblock_order handling

David Hildenbrand
2020-11-12T13:41:02Z

Let's use pageblock_nr_pages and MAX_ORDER_NR_PAGES instead where
possible to simplify.

Add a comment why we have that restriction for now.

Reviewed-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/virtio/virtio_mem.c | 35 +++++++++++++++++++----------------
1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index dee46865bae2..0f9d854e8e42 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -753,14 +753,15 @@ static void virtio_mem_clear_fake_offline(unsigned long pfn,
*/
static void virtio_mem_fake_online(unsigned long pfn, unsigned int nr_pages)
{
- const int order = MAX_ORDER - 1;
+ const unsigned long max_nr_pages = MAX_ORDER_NR_PAGES;
int i;

/*
- * We are always called with subblock granularity, which is at least
- * aligned to MAX_ORDER - 1.
+ * We are always called at least with MAX_ORDER_NR_PAGES
+ * granularity/alignment (e.g., the way subblocks work). All pages
+ * inside such a block are alike.
*/
- for (i = 0; i < nr_pages; i += 1 << order) {
+ for (i = 0; i < nr_pages; i += max_nr_pages) {
struct page *page = pfn_to_page(pfn + i);

/*
@@ -770,14 +771,14 @@ static void virtio_mem_fake_online(unsigned long pfn, unsigned int nr_pages)
* alike.
*/
if (PageDirty(page)) {
- virtio_mem_clear_fake_offline(pfn + i, 1 << order,
+ virtio_mem_clear_fake_offline(pfn + i, max_nr_pages,
false);
- generic_online_page(page, order);
+ generic_online_page(page, MAX_ORDER - 1);
} else {
- virtio_mem_clear_fake_offline(pfn + i, 1 << order,
+ virtio_mem_clear_fake_offline(pfn + i, max_nr_pages,
true);
- free_contig_range(pfn + i, 1 << order);
- adjust_managed_page_count(page, 1 << order);
+ free_contig_range(pfn + i, max_nr_pages);
+ adjust_managed_page_count(page, max_nr_pages);
}
}
}
@@ -790,7 +791,7 @@ static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
int sb_id;

/*
- * We exploit here that subblocks have at least MAX_ORDER - 1
+ * We exploit here that subblocks have at least MAX_ORDER_NR_PAGES.
* size/alignment and that this callback is is called with such a
* size/alignment. So we cannot cross subblocks and therefore
* also not memory blocks.
@@ -1673,13 +1674,15 @@ static int virtio_mem_init(struct virtio_mem *vm)
"Some memory is not addressable. This can make some memory unusable.\n");

/*
- * Calculate the subblock size:
- * - At least MAX_ORDER - 1 / pageblock_order.
- * - At least the device block size.
- * In the worst case, a single subblock per memory block.
+ * 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).
+ * - Is required for now for alloc_contig_range() to work reliably -
+ * it doesn't properly handle smaller granularity on ZONE_NORMAL.
*/
- vm->subblock_size = PAGE_SIZE * 1ul << max_t(uint32_t, MAX_ORDER - 1,
- pageblock_order);
+ vm->subblock_size = max_t(uint64_t, MAX_ORDER_NR_PAGES,
+ pageblock_nr_pages) * PAGE_SIZE;
vm->subblock_size = max_t(uint64_t, vm->device_block_size,
vm->subblock_size);
vm->nb_sb_per_mb = memory_block_size_bytes() / vm->subblock_size;
--
2.26.2