[PATCH RFC] mm: Avoid triggering oom-killer during memory hot-remove operations

[Li Zhijian <lizhijian@fujitsu.com>]

When a process is bound to a node that is being hot-removed, any memory
allocation attempts from that node should fail gracefully without
triggering the OOM-killer. However, the current behavior can cause the
oom-killer to be invoked, leading to the termination of processes on other
nodes, even when there is sufficient memory available in the system.

Prevent the oom-killer from being triggered by processes bound to a
node undergoing hot-remove operations. Instead, the allocation attempts
from the offlining node will simply fail, allowing the process to handle
the failure appropriately without causing disruption to the system.

Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
---
 include/linux/memory_hotplug.h |  6 ++++++
 mm/memory_hotplug.c            | 21 +++++++++++++++++++++
 mm/page_alloc.c                |  6 ++++++
 3 files changed, 33 insertions(+)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 7a9ff464608d..0ca804215e11 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -332,6 +332,7 @@ extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 extern int remove_memory(u64 start, u64 size);
 extern void __remove_memory(u64 start, u64 size);
 extern int offline_and_remove_memory(u64 start, u64 size);
+bool is_offlining_node(nodemask_t nodes);
 
 #else
 static inline void try_offline_node(int nid) {}
@@ -348,6 +349,11 @@ static inline int remove_memory(u64 start, u64 size)
 }
 
 static inline void __remove_memory(u64 start, u64 size) {}
+
+static inline bool is_offlining_node(nodemask_t nodes)
+{
+	return false;
+}
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
 #ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 431b1f6753c0..da3982751ba9 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1938,6 +1938,22 @@ static int count_system_ram_pages_cb(unsigned long start_pfn,
 	return 0;
 }
 
+static nodemask_t offlining_node = NODE_MASK_NONE;
+
+bool is_offlining_node(nodemask_t nodes)
+{
+	return nodes_equal(offlining_node, nodes);
+}
+
+static void offline_pages_start(int node)
+{
+	node_set(node, offlining_node);
+}
+
+static void offline_pages_end(void)
+{
+	offlining_node = NODE_MASK_NONE;
+}
 /*
  * Must be called with mem_hotplug_lock in write mode.
  */
@@ -1991,6 +2007,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 		goto failed_removal;
 	}
 
+	offline_pages_start(node);
 	/*
 	 * Disable pcplists so that page isolation cannot race with freeing
 	 * in a way that pages from isolated pageblock are left on pcplists.
@@ -2107,6 +2124,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 
 	memory_notify(MEM_OFFLINE, &arg);
 	remove_pfn_range_from_zone(zone, start_pfn, nr_pages);
+	offline_pages_end();
+
 	return 0;
 
 failed_removal_isolated:
@@ -2121,6 +2140,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
 		 (unsigned long long) start_pfn << PAGE_SHIFT,
 		 ((unsigned long long) end_pfn << PAGE_SHIFT) - 1,
 		 reason);
+
+	offline_pages_end();
 	return ret;
 }
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1780df31d5f5..acdab6b114a5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3563,6 +3563,12 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 	if (page)
 		goto out;
 
+	/* hot-remove is on-going, it generally fails to allocate memory from
+	 * the being removed memory node. Leave it alone.
+	 */
+	if (is_offlining_node(*ac->nodemask))
+		goto out;
+
 	/* Coredumps can quickly deplete all memory reserves */
 	if (current->flags & PF_DUMPCORE)
 		goto out;
-- 
2.29.2