Re: allowed pages in the block later, was Re: [Ext2-devel] [PATCH] ext3: avoid sending down non-refcounted pages

[Pekka Enberg <penberg@cs.helsinki.fi>]

Hi,

On 12/8/05, Mike Christie <michaelc@cs.wisc.edu> wrote:
> Or there is not a way to do kmalloc(GFP_BLK) that gives us the right
> type of memory is there?

The slab allocator uses page->lru for special purposes. See
page_{set|get}_{cache|slab} in mm/slab.c. They are used by kfree(),
ksize() and slab debugging code to lookup the cache and slab an void
pointer belongs to.

But, if you just need put_page and get_page, couldn't you do something
like the following?

                                       Pekka

Index: 2.6/mm/swap.c
===================================================================
--- 2.6.orig/mm/swap.c
+++ 2.6/mm/swap.c
@@ -36,6 +36,9 @@ int page_cluster;

 void put_page(struct page *page)
 {
+	if (unlikely(PageSlab(page)))
+		return;
+
 	if (unlikely(PageCompound(page))) {
 		page = (struct page *)page_private(page);
 		if (put_page_testzero(page)) {
Index: 2.6/include/linux/mm.h
===================================================================
--- 2.6.orig/include/linux/mm.h
+++ 2.6/include/linux/mm.h
@@ -322,6 +322,9 @@ static inline int page_count(struct page

 static inline void get_page(struct page *page)
 {
+	if (unlikely(PageSlab(page)))
+		return;
+
 	if (unlikely(PageCompound(page)))
 		page = (struct page *)page_private(page);
 	atomic_inc(&page->_count);