[PATCH] mm: catch memory commitment underflow

[Konstantin Khlebnikov]

This adds debug for vm_committed_as under CONFIG_DEBUG_VM=y

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

diff --git a/mm/mmap.c b/mm/mmap.c
index 9d54851..2c7e6aa 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -131,6 +131,12 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 
 	vm_acct_memory(pages);
 
+#ifdef CONFIG_DEBUG_VM
+	WARN_ONCE(percpu_counter_read(&vm_committed_as) <
+			-(s64)vm_committed_as_batch * num_online_cpus(),
+			"memory commitment underflow");
+#endif
+
 	/*
 	 * Sometimes we want to use more memory than we have
 	 */

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