[PATCH 3/3] mm: catch memory commitment underflow

[Konstantin Khlebnikov]

This patch prints warning (if CONFIG_DEBUG_VM=y) when
memory commitment becomes too negative.

Signed-off-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
---
 mm/mmap.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index 129b847..d3decd9 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -134,6 +134,12 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 {
 	unsigned long free, allowed, reserve;
 
+#ifdef CONFIG_DEBUG_VM
+	WARN_ONCE(percpu_counter_read(&vm_committed_as) <
+			-(s64)vm_committed_as_batch * num_online_cpus(),
+			"memory commitment underflow");
+#endif
+
 	vm_acct_memory(pages);
 
 	/*

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