From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Now that we can detect writers of shared mappings, throttle them.  Avoids OOM
by surprise.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/memory.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff -puN mm/memory.c~throttle-writers-of-shared-mappings mm/memory.c
--- devel/mm/memory.c~throttle-writers-of-shared-mappings	2006-05-17 13:09:45.000000000 -0700
+++ devel-akpm/mm/memory.c	2006-05-17 13:09:45.000000000 -0700
@@ -49,6 +49,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/backing-dev.h>
+#include <linux/writeback.h>
 
 #include <asm/pgalloc.h>
 #include <asm/uaccess.h>
@@ -2163,8 +2164,11 @@ retry:
 unlock:
 	pte_unmap_unlock(page_table, ptl);
 	if (dirty_page) {
+		struct address_space *mapping = page_mapping(dirty_page);
 		set_page_dirty(dirty_page);
 		put_page(dirty_page);
+		if (mapping)
+			balance_dirty_pages_ratelimited_nr(mapping, 1);
 	}
 	return ret;
 oom:
@@ -2284,8 +2288,11 @@ static inline int handle_pte_fault(struc
 unlock:
 	pte_unmap_unlock(pte, ptl);
 	if (dirty_page) {
+		struct address_space *mapping = page_mapping(dirty_page);
 		set_page_dirty(dirty_page);
 		put_page(dirty_page);
+		if (mapping)
+			balance_dirty_pages_ratelimited_nr(mapping, 1);
 	}
 	return VM_FAULT_MINOR;
 }
_