[RFC][PATCH 3/8] mm: Add vma sequence count

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

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In order to detect VMA range changes, add a sequence count.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 include/linux/mm_types.h |    2 ++
 mm/mmap.c                |   10 ++++++++++
 2 files changed, 12 insertions(+)

Index: linux-2.6/include/linux/mm_types.h
===================================================================
--- linux-2.6.orig/include/linux/mm_types.h
+++ linux-2.6/include/linux/mm_types.h
@@ -12,6 +12,7 @@
 #include <linux/completion.h>
 #include <linux/cpumask.h>
 #include <linux/page-debug-flags.h>
+#include <linux/seqlock.h>
 #include <asm/page.h>
 #include <asm/mmu.h>
 
@@ -186,6 +187,7 @@ struct vm_area_struct {
 #ifdef CONFIG_NUMA
 	struct mempolicy *vm_policy;	/* NUMA policy for the VMA */
 #endif
+	seqcount_t vm_sequence;
 };
 
 struct core_thread {
Index: linux-2.6/mm/mmap.c
===================================================================
--- linux-2.6.orig/mm/mmap.c
+++ linux-2.6/mm/mmap.c
@@ -512,6 +512,10 @@ void vma_adjust(struct vm_area_struct *v
 	long adjust_next = 0;
 	int remove_next = 0;
 
+	write_seqcount_begin(&vma->vm_sequence);
+	if (next)
+		write_seqcount_begin(&next->vm_sequence);
+
 	if (next && !insert) {
 		if (end >= next->vm_end) {
 			/*
@@ -647,11 +651,17 @@ again:			remove_next = 1 + (end > next->
 		 * up the code too much to do both in one go.
 		 */
 		if (remove_next == 2) {
+			write_seqcount_end(&next->vm_sequence);
 			next = vma->vm_next;
+			write_seqcount_begin(&next->vm_sequence);
 			goto again;
 		}
 	}
 
+	if (next)
+		write_seqcount_end(&next->vm_sequence);
+	write_seqcount_end(&vma->vm_sequence);
+
 	validate_mm(mm);
 }
 

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