From c5d41d116208522809ea391c3d89203d4470bc4c Mon Sep 17 00:00:00 2001
From: Liam Mark <lmark@codeaurora.org>
Date: Wed, 23 May 2018 10:56:12 -0700
Subject: [PATCH] mm, oom: Try to online memory block before killing

Before killing a process first try to see if there are any offlined
memory blocks, if there are try to online one of them.

Change-Id: Ie97c8b69f0ba173c202a891a38a5c914869ddaae
Signed-off-by: Liam Mark <lmark@codeaurora.org>
[isaacm@codeaurora.org: Update walk_memory_range to walk_memory_blocks]
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
---
 include/linux/memory_hotplug.h |  6 ++++++
 mm/memory_hotplug.c            | 34 ++++++++++++++++++++++++++++++++++
 mm/oom_kill.c                  |  7 +++++++
 3 files changed, 47 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index f46ea71b4ffd..fc1819b467b3 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -110,6 +110,7 @@ extern void __online_page_increment_counters(struct page *page);
 extern void __online_page_free(struct page *page);
 
 extern int try_online_node(int nid);
+extern bool try_online_one_block(int nid);
 
 extern int arch_add_memory(int nid, u64 start, u64 size,
 			struct mhp_restrictions *restrictions);
@@ -269,6 +270,11 @@ static inline int try_online_node(int nid)
 	return 0;
 }
 
+static inline bool try_online_one_block(int nid)
+{
+	return false;
+}
+
 static inline void get_online_mems(void) {}
 static inline void put_online_mems(void) {}
 
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 3b287f3ba11c..fadddfdc6f9c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -999,6 +999,40 @@ int try_online_node(int nid)
 	return ret;
 }
 
+static int online_memory_one_block(struct memory_block *mem, void *arg)
+{
+	bool *onlined_block = (bool *)arg;
+	int ret;
+
+	if (*onlined_block || !is_memblock_offlined(mem))
+		return 0;
+
+	ret = device_online(&mem->dev);
+	if (!ret)
+		*onlined_block = true;
+
+	return 0;
+}
+
+bool try_online_one_block(int nid)
+{
+	struct zone *zone = &NODE_DATA(nid)->node_zones[ZONE_MOVABLE];
+	unsigned long zone_start, zone_size;
+	bool onlined_block = false;
+	int ret = lock_device_hotplug_sysfs();
+
+	if (ret)
+		return false;
+
+	zone_start = PFN_PHYS(zone->zone_start_pfn);
+	zone_size = zone->spanned_pages << PAGE_SHIFT;
+	walk_memory_blocks(zone_start, zone_size, &onlined_block,
+			   online_memory_one_block);
+
+	unlock_device_hotplug();
+	return onlined_block;
+}
+
 static int check_hotplug_memory_range(u64 start, u64 size)
 {
 	/* memory range must be block size aligned */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 6993791a517b..087e0c1b2fdf 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -43,6 +43,7 @@
 #include <linux/init.h>
 #include <linux/mmu_notifier.h>
 #include <linux/show_mem_notifier.h>
+#include <linux/memory_hotplug.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -1066,6 +1067,12 @@ bool out_of_memory(struct oom_control *oc)
 	if (oom_killer_disabled)
 		return false;
 
+	if (try_online_one_block(numa_node_id())) {
+		/* Got some memory back */
+		WARN(1, "OOM killer had to online a memory block\n");
+		return true;
+	}
+
 	if (!is_memcg_oom(oc)) {
 		blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
 		if (freed > 0)