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-rw-r--r--include/linux/ksm.h31
1 files changed, 27 insertions, 4 deletions
diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index a485c14ecd5d..2d64ff30c0de 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -12,11 +12,14 @@
#include <linux/sched.h>
#include <linux/vmstat.h>
+struct mmu_gather;
+
#ifdef CONFIG_KSM
int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
unsigned long end, int advice, unsigned long *vm_flags);
int __ksm_enter(struct mm_struct *mm);
-void __ksm_exit(struct mm_struct *mm);
+void __ksm_exit(struct mm_struct *mm,
+ struct mmu_gather **tlbp, unsigned long end);
static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
{
@@ -25,10 +28,24 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
return 0;
}
-static inline void ksm_exit(struct mm_struct *mm)
+/*
+ * For KSM to handle OOM without deadlock when it's breaking COW in a
+ * likely victim of the OOM killer, exit_mmap() has to serialize with
+ * ksm_exit() after freeing mm's pages but before freeing its page tables.
+ * That leaves a window in which KSM might refault pages which have just
+ * been finally unmapped: guard against that with ksm_test_exit(), and
+ * use it after getting mmap_sem in ksm.c, to check if mm is exiting.
+ */
+static inline bool ksm_test_exit(struct mm_struct *mm)
+{
+ return atomic_read(&mm->mm_users) == 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm,
+ struct mmu_gather **tlbp, unsigned long end)
{
if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
- __ksm_exit(mm);
+ __ksm_exit(mm, tlbp, end);
}
/*
@@ -64,7 +81,13 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
return 0;
}
-static inline void ksm_exit(struct mm_struct *mm)
+static inline bool ksm_test_exit(struct mm_struct *mm)
+{
+ return 0;
+}
+
+static inline void ksm_exit(struct mm_struct *mm,
+ struct mmu_gather **tlbp, unsigned long end)
{
}