[RFC PATCH 4/10] debug page_file_cache

Rik van Riel
2007-11-03T22:55:37Z

Debug whether we end up classifying the wrong pages as
filesystem backed. This has not triggered in stress
tests on my system, but who knows...

Signed-off-by: Rik van Riel <riel@redhat.com>

Index: linux-2.6.23-mm1/include/linux/mm_inline.h
===================================================================
--- linux-2.6.23-mm1.orig/include/linux/mm_inline.h
+++ linux-2.6.23-mm1/include/linux/mm_inline.h
@@ -1,6 +1,8 @@
#ifndef LINUX_MM_INLINE_H
#define LINUX_MM_INLINE_H

+#include <linux/fs.h> /* for struct address_space */
+
/**
* page_file_cache(@page)
* Returns !0 if @page is page cache page backed by a regular file,
@@ -9,11 +11,19 @@
* We would like to get this info without a page flag, but the state
* needs to propagate to whereever the page is last deleted from the LRU.
*/
+extern const struct address_space_operations shmem_aops;
static inline int page_file_cache(struct page *page)
{
+ struct address_space * mapping = page_mapping(page);
+
if (PageSwapBacked(page))
return 0;

+ /* These pages should all be marked PG_swapbacked */
+ WARN_ON(PageAnon(page));
+ WARN_ON(PageSwapCache(page));
+ WARN_ON(mapping && mapping->a_ops && mapping->a_ops == &shmem_aops);
+
/* The page is page cache backed by a normal filesystem. */
return 2;
}
Index: linux-2.6.23-mm1/mm/shmem.c
===================================================================
--- linux-2.6.23-mm1.orig/mm/shmem.c
+++ linux-2.6.23-mm1/mm/shmem.c
@@ -180,7 +180,7 @@ static inline void shmem_unacct_blocks(u
}

static const struct super_operations shmem_ops;
-static const struct address_space_operations shmem_aops;
+const struct address_space_operations shmem_aops;
static const struct file_operations shmem_file_operations;
static const struct inode_operations shmem_inode_operations;
static const struct inode_operations shmem_dir_inode_operations;
@@ -2344,7 +2344,7 @@ static void destroy_inodecache(void)
kmem_cache_destroy(shmem_inode_cachep);
}

-static const struct address_space_operations shmem_aops = {
+const struct address_space_operations shmem_aops = {
.writepage = shmem_writepage,
.set_page_dirty = __set_page_dirty_no_writeback,
#ifdef CONFIG_TMPFS