KSM broken in the CONFIG_MMU=n case

KSM broken in the CONFIG_MMU=n case

[David Howells]

Hi Hugh,

The KSM code is broken in the CONFIG_MMU=n case as enum ttu_flags is required,
but not defined.  Simply predeclaring it doesn't help as the argument isn't a
pointer to a value of that type.

I've attached a patch below to deal with it; it's a bit messy, though, as the
fallback ksm_exit() is required in both the NOMMU and no-KSM cases.

David
---
From: David Howells <dhowells@redhat.com>
Subject: [PATCH] NOMMU: Fix KSM in the CONFIG_MMU=n case

Fix KSM in the CONFIG_MMU=n case:

In file included from kernel/fork.c:52:
include/linux/ksm.h:129: warning: 'enum ttu_flags' declared inside parameter list
include/linux/ksm.h:129: warning: its scope is only this definition or declaration, which is probably not what you want
include/linux/ksm.h:129: error: parameter 2 ('flags') has incomplete type

by making most of linux/ksm.h contingent on CONFIG_MMU=y.  The fallback
version of ksm_exit() requires special handling as that is also used in the
MMU=y, KSM=n case.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 include/linux/ksm.h |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)


diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index bed5f16..7f1e1f0 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -16,6 +16,7 @@
 struct stable_node;
 struct mem_cgroup;
 
+#ifdef CONFIG_MMU
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags);
@@ -105,10 +106,6 @@ 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 int PageKsm(struct page *page)
 {
 	return 0;
@@ -141,5 +138,12 @@ static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 {
 }
 #endif /* !CONFIG_KSM */
+#endif /* CONFIG_MMU */
+
+#if !defined(CONFIG_MMU) || !defined(CONFIG_KSM)
+static inline void ksm_exit(struct mm_struct *mm)
+{
+}
+#endif
 
 #endif /* __LINUX_KSM_H */

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