[PATCH] UBUNTU: SAUCE: Fix revert "mm, memory_hotplug: do not associate hotadded memory to zones until online

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

BugLink: http://bugs.launchpad.net/bugs/1761104

Bug fix #1747069 causes an issue for NVIDIA drivers on ppc64el platforms.
According to Will Davis at NVIDIA:

"- The original patch 3d79a728f9b2e6ddcce4e02c91c4de1076548a4c changed
the call to arch_add_memory in mm/memory_hotplug.c to call with the
boolean argument set to true instead of false, and inverted the
semantics of that argument in the arch layers.

- The revert patch 4fe85d5a7c50f003fe4863a1a87f5d8cc121c75c reverted the
semantic change in the arch layers, but didn't revert the change to the
arch_add_memory call in mm/memory_hotplug.c"

And also:

"It looks like the problem here is that the online_type is _MOVABLE but
can_online_high_movable(nid=255) is returning false:

        if ((zone_idx(zone) > ZONE_NORMAL ||
            online_type == MMOP_ONLINE_MOVABLE) &&
            !can_online_high_movable(pfn_to_nid(pfn)))

This check was removed by upstream commit
57c0a17238e22395428248c53f8e390c051c88b8, and I've verified that if I
apply that commit (partially) to the 4.13.0-37.42 tree along with the
previous arch_add_memory patch to make the probe work, I can fully online
the GPU device memory as expected.

Commit 57c0a172.. implies that the can_online_high_movable() checks
weren't useful anyway, so in addition to the arch_add_memory fix, does
it make sense to revert the pieces of
4fe85d5a7c50f003fe4863a1a87f5d8cc121c75c that added back the
can_online_high_movable() check?"

This patch fixes the partial backport from bug #1747069, by removing
can_online_high_movable and fix the incorrectly set boolean argument
to arch_add_memory().

I've exercised this fix through the ADT tests for i386, amd64 and
ppc64el (in VMs) and observe no regressions.

Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 mm/memory_hotplug.c | 31 +------------------------------
 1 file changed, 1 insertion(+), 30 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a4724e7..c1f9677 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -883,23 +883,6 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 	return 0;
 }
 
-#ifdef CONFIG_MOVABLE_NODE
-/*
- * When CONFIG_MOVABLE_NODE, we permit onlining of a node which doesn't have
- * normal memory.
- */
-static bool can_online_high_movable(int nid)
-{
-	return true;
-}
-#else /* CONFIG_MOVABLE_NODE */
-/* ensure every online node has NORMAL memory */
-static bool can_online_high_movable(int nid)
-{
-	return node_state(nid, N_NORMAL_MEMORY);
-}
-#endif /* CONFIG_MOVABLE_NODE */
-
 /* check which state of node_states will be changed when online memory */
 static void node_states_check_changes_online(unsigned long nr_pages,
 	struct zone *zone, struct memory_notify *arg)
@@ -1021,18 +1004,6 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	struct memory_notify arg;
 	int zone_shift = 0;
 
-	/*
-	 * This doesn't need a lock to do pfn_to_page().
-	 * The section can't be removed here because of the
-	 * memory_block->state_mutex.
-	 */
-	zone = page_zone(pfn_to_page(pfn));
-
-	if ((zone_idx(zone) > ZONE_NORMAL ||
-	    online_type == MMOP_ONLINE_MOVABLE) &&
-	    !can_online_high_movable(pfn_to_nid(pfn)))
-		return -EINVAL;
-
 	if (online_type == MMOP_ONLINE_KERNEL) {
 		if (!zone_can_shift(pfn, nr_pages, ZONE_NORMAL, &zone_shift))
 			return -EINVAL;
@@ -1323,7 +1294,7 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
 	}
 
 	/* call arch's memory hotadd */
-	ret = arch_add_memory(nid, start, size, true);
+	ret = arch_add_memory(nid, start, size, false);
 
 	if (ret < 0)
 		goto error;
-- 
2.7.4