Patch from Dave McCracken <dmccr@us.ibm.com>

Convert page.pte.mapcount to an int, move its manipulation inside
pte_chain_lock().



 25-akpm/include/linux/mm.h |    2 +-
 25-akpm/mm/rmap.c          |   27 +++++++++++++++------------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff -puN include/linux/mm.h~objrmap-atomic_t-fix include/linux/mm.h
--- 25/include/linux/mm.h~objrmap-atomic_t-fix	Tue Mar  4 13:13:48 2003
+++ 25-akpm/include/linux/mm.h	Tue Mar  4 13:13:48 2003
@@ -172,7 +172,7 @@ struct page {
 		struct pte_chain *chain;/* Reverse pte mapping pointer.
 					 * protected by PG_chainlock */
 		pte_addr_t direct;
-		atomic_t mapcount;
+		int mapcount;
 	} pte;
 	unsigned long private;		/* mapping-private opaque data */
 
diff -puN mm/rmap.c~objrmap-atomic_t-fix mm/rmap.c
--- 25/mm/rmap.c~objrmap-atomic_t-fix	Tue Mar  4 13:13:48 2003
+++ 25-akpm/mm/rmap.c	Tue Mar  4 13:13:48 2003
@@ -144,7 +144,7 @@ page_referenced_obj(struct page *page)
 	struct vm_area_struct *vma;
 	int referenced = 0;
 
-	if (atomic_read(&page->pte.mapcount) == 0)
+	if (!page->pte.mapcount)
 		return 0;
 
 	if (!mapping)
@@ -243,19 +243,20 @@ page_add_rmap(struct page *page, pte_t *
 	if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
 		return pte_chain;
 
+	pte_chain_lock(page);
+
 	if (!PageAnon(page)) {
 		if (!page->mapping)
 			BUG();
 		if (PageSwapCache(page))
 			BUG();
-		if (atomic_read(&page->pte.mapcount) == 0)
+		if (!page->pte.mapcount)
 			inc_page_state(nr_mapped);
-		atomic_inc(&page->pte.mapcount);
+		page->pte.mapcount++;
+		pte_chain_unlock(page);
 		return pte_chain;
 	}
 
-	pte_chain_lock(page);
-
 #ifdef DEBUG_RMAP
 	/*
 	 * This stuff needs help to get up to highmem speed.
@@ -342,20 +343,22 @@ void page_remove_rmap(struct page * page
 	if (!page_mapped(page))
 		return;		/* remap_page_range() from a driver? */
 
+	pte_chain_lock(page);
+
 	if (!PageAnon(page)) {
 		if (!page->mapping)
 			BUG();
 		if (PageSwapCache(page))
 			BUG();
-		if (atomic_read(&page->pte.mapcount) == 0)
+		if (!page->pte.mapcount)
 			BUG();
-		if (atomic_dec_and_test(&page->pte.mapcount))
+		page->pte.mapcount--;
+		if (!page->pte.mapcount)
 			dec_page_state(nr_mapped);
+		pte_chain_unlock(page);
 		return;
 	}
 
-	pte_chain_lock(page);
-
 	if (PageDirect(page)) {
 		if (page->pte.direct == pte_paddr) {
 			page->pte.direct = 0;
@@ -471,11 +474,11 @@ try_to_unmap_obj_one(struct vm_area_stru
 	if (pte_dirty(pteval))
 		set_page_dirty(page);
 
-	if (atomic_read(&page->pte.mapcount) == 0)
+	if (!page->pte.mapcount)
 		BUG();
 
 	mm->rss--;
-	atomic_dec(&page->pte.mapcount);
+	page->pte.mapcount--;
 	page_cache_release(page);
 
 out_unmap:
@@ -516,7 +519,7 @@ try_to_unmap_obj(struct page *page)
 			goto out;
 	}
 
-	if (atomic_read(&page->pte.mapcount) != 0)
+	if (page->pte.mapcount)
 		BUG();
 
 out:

_