Prev: [PATCH -mmotm 02/30] Swap over network documentation
Next: [PATCH -mmotm 27/30] nfs: fix various memory recursions possible with swap over NFS
From: Xiaotian Feng on 13 Jul 2010 06:30
From 50e813068c51de733bbbdd04eb4af9c43919cd57 Mon Sep 17 00:00:00 2001
From: Xiaotian Feng <dfeng(a)redhat.com>
Date: Tue, 13 Jul 2010 13:09:50 +0800
Subject: [PATCH 23/30] mm: methods for teaching filesystems about PG_swapcache pages

In order to teach filesystems to handle swap cache pages, three new page
functions are introduced:

pgoff_t page_file_index(struct page *);
loff_t page_file_offset(struct page *);
struct address_space *page_file_mapping(struct page *);

page_file_index() - gives the offset of this page in the file in
PAGE_CACHE_SIZE blocks. Like page->index is for mapped pages, this function
also gives the correct index for PG_swapcache pages.

page_file_offset() - uses page_file_index(), so that it will give the expected
result, even for PG_swapcache pages.

page_file_mapping() - gives the mapping backing the actual page; that is for
swap cache pages it will give swap_file->f_mapping.

Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
Signed-off-by: Suresh Jayaraman <sjayaraman(a)suse.de>
Signed-off-by: Xiaotian Feng <dfeng(a)redhat.com>
---
include/linux/mm.h | 25 +++++++++++++++++++++++++
include/linux/pagemap.h | 5 +++++
mm/swapfile.c | 19 +++++++++++++++++++
3 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 32033ba..0cf97fc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -663,6 +663,17 @@ static inline void *page_rmapping(struct page *page)
return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
}

+extern struct address_space *__page_file_mapping(struct page *);
+
+static inline
+struct address_space *page_file_mapping(struct page *page)
+{
+ if (unlikely(PageSwapCache(page)))
+ return __page_file_mapping(page);
+
+ return page->mapping;
+}
+
static inline int PageAnon(struct page *page)
{
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
@@ -679,6 +690,20 @@ static inline pgoff_t page_index(struct page *page)
return page->index;
}

+extern pgoff_t __page_file_index(struct page *page);
+
+/*
+ * Return the file index of the page. Regular pagecache pages use ->index
+ * whereas swapcache pages use swp_offset(->private)
+ */
+static inline pgoff_t page_file_index(struct page *page)
+{
+ if (unlikely(PageSwapCache(page)))
+ return __page_file_index(page);
+
+ return page->index;
+}
+
/*
* The atomic page->_mapcount, like _count, starts from -1:
* so that transitions both from it and to it can be tracked,
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index e12cdc6..64eda5b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -285,6 +285,11 @@ static inline loff_t page_offset(struct page *page)
extern pgoff_t linear_hugepage_index(struct vm_area_struct *vma,
unsigned long address);

+static inline loff_t page_file_offset(struct page *page)
+{
+ return ((loff_t)page_file_index(page)) << PAGE_CACHE_SHIFT;
+}
+
static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
unsigned long address)
{
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a7baef1..d8a05e4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2261,6 +2261,25 @@ struct swap_info_struct *page_swap_info(struct page *page)
}

/*
+ * out-of-line __page_file_ methods to avoid include hell.
+ */
+
+struct address_space *__page_file_mapping(struct page *page)
+{
+ VM_BUG_ON(!PageSwapCache(page));
+ return page_swap_info(page)->swap_file->f_mapping;
+}
+EXPORT_SYMBOL_GPL(__page_file_mapping);
+
+pgoff_t __page_file_index(struct page *page)
+{
+ swp_entry_t swap = { .val = page_private(page) };
+ VM_BUG_ON(!PageSwapCache(page));
+ return swp_offset(swap);
+}
+EXPORT_SYMBOL_GPL(__page_file_index);
+
+/*
* swap_lock prevents swap_map being freed. Don't grab an extra
* reference on the swaphandle, it doesn't matter if it becomes unused.
*/
--
1.7.1.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
 | 
Pages: 1
Prev: [PATCH -mmotm 02/30] Swap over network documentation
Next: [PATCH -mmotm 27/30] nfs: fix various memory recursions possible with swap over NFS