thp: madvise(MADV_NOHUGEPAGE)

Add madvise MADV_NOHUGEPAGE to mark regions that are not important to be
hugepage backed.  Return -EINVAL if the vma is not of an anonymous type,
or the feature isn't built into the kernel.  Never silently return
success.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/huge_mm.h

@@ -52,10 +52,12 @@ extern pmd_t *page_check_address_pmd(struct page *page,
 #define HPAGE_PMD_SIZE HPAGE_SIZE
 
 #define transparent_hugepage_enabled(__vma)				\
-	(transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_FLAG) ||	\
+	((transparent_hugepage_flags &					\
+	  (1<<TRANSPARENT_HUGEPAGE_FLAG) ||				\
 	  (transparent_hugepage_flags &					\
 	   (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG) &&			\
-	  (__vma)->vm_flags & VM_HUGEPAGE))
+	   ((__vma)->vm_flags & VM_HUGEPAGE))) &&			\
+	 !((__vma)->vm_flags & VM_NOHUGEPAGE))
 #define transparent_hugepage_defrag(__vma)				\
 	((transparent_hugepage_flags &					\
 	  (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)) ||			\
@@ -103,7 +105,7 @@ extern void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd);
 #if HPAGE_PMD_ORDER > MAX_ORDER
 #error "hugepages can't be allocated by the buddy allocator"
 #endif
-extern int hugepage_madvise(unsigned long *vm_flags);
+extern int hugepage_madvise(unsigned long *vm_flags, int advice);
 extern void __vma_adjust_trans_huge(struct vm_area_struct *vma,
 				    unsigned long start,
 				    unsigned long end,
@@ -141,7 +143,7 @@ static inline int split_huge_page(struct page *page)
 	do { } while (0)
 #define wait_split_huge_page(__anon_vma, __pmd)	\
 	do { } while (0)
-static inline int hugepage_madvise(unsigned long *vm_flags)
+static inline int hugepage_madvise(unsigned long *vm_flags, int advice)
 {
 	BUG();
 	return 0;

include/linux/khugepaged.h

@@ -38,9 +38,10 @@ static inline void khugepaged_exit(struct mm_struct *mm)
 static inline int khugepaged_enter(struct vm_area_struct *vma)
 {
 	if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
-		if (khugepaged_always() ||
+		if ((khugepaged_always() ||
 		     (khugepaged_req_madv() &&
-		     vma->vm_flags & VM_HUGEPAGE))
+		      vma->vm_flags & VM_HUGEPAGE)) &&
+		    !(vma->vm_flags & VM_NOHUGEPAGE))
 			if (__khugepaged_enter(vma->vm_mm))
 				return -ENOMEM;
 	return 0;

include/linux/mm.h

@@ -83,6 +83,7 @@ extern unsigned int kobjsize(const void *objp);
 #define VM_GROWSUP	0x00000200
 #else
 #define VM_GROWSUP	0x00000000
+#define VM_NOHUGEPAGE	0x00000200	/* MADV_NOHUGEPAGE marked this vma */
 #endif
 #define VM_PFNMAP	0x00000400	/* Page-ranges managed without "struct page", just pure PFN */
 #define VM_DENYWRITE	0x00000800	/* ETXTBSY on write attempts.. */

mm/huge_memory.c

@@ -16,6 +16,7 @@
 #include <linux/kthread.h>
 #include <linux/khugepaged.h>
 #include <linux/freezer.h>
+#include <linux/mman.h>
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
 #include "internal.h"
@@ -1388,18 +1389,36 @@ int split_huge_page(struct page *page)
 	return ret;
 }
 
-int hugepage_madvise(unsigned long *vm_flags)
+int hugepage_madvise(unsigned long *vm_flags, int advice)
 {
+	switch (advice) {
+	case MADV_HUGEPAGE:
 		/*
 		 * Be somewhat over-protective like KSM for now!
 		 */
-	if (*vm_flags & (VM_HUGEPAGE | VM_SHARED  | VM_MAYSHARE   |
+		if (*vm_flags & (VM_HUGEPAGE |
+				 VM_SHARED   | VM_MAYSHARE   |
 				 VM_PFNMAP   | VM_IO      | VM_DONTEXPAND |
 				 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
 				 VM_MIXEDMAP | VM_SAO))
 			return -EINVAL;
-
+		*vm_flags &= ~VM_NOHUGEPAGE;
 		*vm_flags |= VM_HUGEPAGE;
+		break;
+	case MADV_NOHUGEPAGE:
+		/*
+		 * Be somewhat over-protective like KSM for now!
+		 */
+		if (*vm_flags & (VM_NOHUGEPAGE |
+				 VM_SHARED   | VM_MAYSHARE   |
+				 VM_PFNMAP   | VM_IO      | VM_DONTEXPAND |
+				 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
+				 VM_MIXEDMAP | VM_SAO))
+			return -EINVAL;
+		*vm_flags &= ~VM_HUGEPAGE;
+		*vm_flags |= VM_NOHUGEPAGE;
+		break;
+	}
 
 	return 0;
 }

mm/madvise.c

@@ -72,7 +72,8 @@ static long madvise_behavior(struct vm_area_struct * vma,
 			goto out;
 		break;
 	case MADV_HUGEPAGE:
-		error = hugepage_madvise(&new_flags);
+	case MADV_NOHUGEPAGE:
+		error = hugepage_madvise(&new_flags, behavior);
 		if (error)
 			goto out;
 		break;
@@ -290,6 +291,7 @@ madvise_behavior_valid(int behavior)
 #endif
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	case MADV_HUGEPAGE:
+	case MADV_NOHUGEPAGE:
 #endif
 		return 1;