[patch 3/4] mmu_notifier: invalidate_page callbacks for subsystems with rmap

[Christoph Lameter <clameter-sJ/iWh9BUns@public.gmane.org>]

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Callbacks to remove individual pages if the subsystem has an
rmap capability. The pagelock is held but no spinlocks are held.
The refcount of the page is elevated so that dropping the refcount
in the subsystem will not directly free the page.

The callbacks occur after the Linux rmaps have been walked.

Robin: We do not hold the page lock in __xip_unmap().
I guess we do not need to increase the refcount there since the
page is static and cannot go away?

Signed-off-by: Christoph Lameter <clameter-sJ/iWh9BUns@public.gmane.org>

Index: linux-2.6/mm/filemap_xip.c
===================================================================
--- linux-2.6.orig/mm/filemap_xip.c	2008-01-24 19:47:28.000000000 -0800
+++ linux-2.6/mm/filemap_xip.c	2008-01-24 20:30:31.000000000 -0800
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/uio.h>
 #include <linux/rmap.h>
+#include <linux/mmu_notifier.h>
 #include <linux/sched.h>
 #include <asm/tlbflush.h>
 
@@ -183,6 +184,9 @@ __xip_unmap (struct address_space * mapp
 	if (!page)
 		return;
 
+	if (PageExternalRmap(page))
+		mmu_rmap_notifier(invalidate_page, page);
+
 	spin_lock(&mapping->i_mmap_lock);
 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 		mm = vma->vm_mm;
Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c	2008-01-24 19:47:28.000000000 -0800
+++ linux-2.6/mm/rmap.c	2008-01-24 20:30:31.000000000 -0800
@@ -49,6 +49,7 @@
 #include <linux/rcupdate.h>
 #include <linux/module.h>
 #include <linux/kallsyms.h>
+#include <linux/mmu_notifier.h>
 
 #include <asm/tlbflush.h>
 
@@ -473,6 +474,8 @@ int page_mkclean(struct page *page)
 		struct address_space *mapping = page_mapping(page);
 		if (mapping) {
 			ret = page_mkclean_file(mapping, page);
+			if (unlikely(PageExternalRmap(page)))
+				mmu_rmap_notifier(invalidate_page, page);
 			if (page_test_dirty(page)) {
 				page_clear_dirty(page);
 				ret = 1;
@@ -971,6 +974,9 @@ int try_to_unmap(struct page *page, int 
 	else
 		ret = try_to_unmap_file(page, migration);
 
+	if (unlikely(PageExternalRmap(page)))
+		mmu_rmap_notifier(invalidate_page, page);
+
 	if (!page_mapped(page))
 		ret = SWAP_SUCCESS;
 	return ret;

-- 

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