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Subject[PATCH 22/29] mm: prepare swap entry methods for use in page methods
Move around the swap entry methods in preparation for use from
page methods.

Also provide a function to obtain the swap_info_struct backing
a swap cache page.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/mm.h | 8 +++++++
include/linux/swap.h | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/swapops.h | 44 -------------------------------------------
mm/swapfile.c | 1
4 files changed, 58 insertions(+), 44 deletions(-)

Index: linux-2.6/include/linux/mm.h
===================================================================
--- linux-2.6.orig/include/linux/mm.h
+++ linux-2.6/include/linux/mm.h
@@ -13,6 +13,7 @@
#include <linux/debug_locks.h>
#include <linux/mm_types.h>
#include <linux/security.h>
+#include <linux/swap.h>

struct mempolicy;
struct anon_vma;
@@ -600,6 +601,13 @@ static inline struct address_space *page
return mapping;
}

+static inline struct swap_info_struct *page_swap_info(struct page *page)
+{
+ swp_entry_t swap = { .val = page_private(page) };
+ BUG_ON(!PageSwapCache(page));
+ return get_swap_info_struct(swp_type(swap));
+}
+
static inline int PageAnon(struct page *page)
{
return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
Index: linux-2.6/include/linux/swap.h
===================================================================
--- linux-2.6.orig/include/linux/swap.h
+++ linux-2.6/include/linux/swap.h
@@ -80,6 +80,50 @@ typedef struct {
} swp_entry_t;

/*
+ * swapcache pages are stored in the swapper_space radix tree. We want to
+ * get good packing density in that tree, so the index should be dense in
+ * the low-order bits.
+ *
+ * We arrange the `type' and `offset' fields so that `type' is at the five
+ * high-order bits of the swp_entry_t and `offset' is right-aligned in the
+ * remaining bits.
+ *
+ * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
+ */
+#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT)
+#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1)
+
+/*
+ * Store a type+offset into a swp_entry_t in an arch-independent format
+ */
+static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
+{
+ swp_entry_t ret;
+
+ ret.val = (type << SWP_TYPE_SHIFT(ret)) |
+ (offset & SWP_OFFSET_MASK(ret));
+ return ret;
+}
+
+/*
+ * Extract the `type' field from a swp_entry_t. The swp_entry_t is in
+ * arch-independent format
+ */
+static inline unsigned swp_type(swp_entry_t entry)
+{
+ return (entry.val >> SWP_TYPE_SHIFT(entry));
+}
+
+/*
+ * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
+ * arch-independent format
+ */
+static inline pgoff_t swp_offset(swp_entry_t entry)
+{
+ return entry.val & SWP_OFFSET_MASK(entry);
+}
+
+/*
* current->reclaim_state points to one of these when a task is running
* memory reclaim
*/
@@ -321,6 +365,11 @@ static inline struct page *lookup_swap_c
return NULL;
}

+static inline struct swap_info_struct *get_swap_info_struct(unsigned type)
+{
+ return NULL;
+}
+
#define can_share_swap_page(p) (page_mapcount(p) == 1)

static inline int move_to_swap_cache(struct page *page, swp_entry_t entry)
Index: linux-2.6/include/linux/swapops.h
===================================================================
--- linux-2.6.orig/include/linux/swapops.h
+++ linux-2.6/include/linux/swapops.h
@@ -1,47 +1,3 @@
-/*
- * swapcache pages are stored in the swapper_space radix tree. We want to
- * get good packing density in that tree, so the index should be dense in
- * the low-order bits.
- *
- * We arrange the `type' and `offset' fields so that `type' is at the five
- * high-order bits of the swp_entry_t and `offset' is right-aligned in the
- * remaining bits.
- *
- * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
- */
-#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT)
-#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1)
-
-/*
- * Store a type+offset into a swp_entry_t in an arch-independent format
- */
-static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
-{
- swp_entry_t ret;
-
- ret.val = (type << SWP_TYPE_SHIFT(ret)) |
- (offset & SWP_OFFSET_MASK(ret));
- return ret;
-}
-
-/*
- * Extract the `type' field from a swp_entry_t. The swp_entry_t is in
- * arch-independent format
- */
-static inline unsigned swp_type(swp_entry_t entry)
-{
- return (entry.val >> SWP_TYPE_SHIFT(entry));
-}
-
-/*
- * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
- * arch-independent format
- */
-static inline pgoff_t swp_offset(swp_entry_t entry)
-{
- return entry.val & SWP_OFFSET_MASK(entry);
-}
-
/* check whether a pte points to a swap entry */
static inline int is_swap_pte(pte_t pte)
{
Index: linux-2.6/mm/swapfile.c
===================================================================
--- linux-2.6.orig/mm/swapfile.c
+++ linux-2.6/mm/swapfile.c
@@ -1795,6 +1795,7 @@ get_swap_info_struct(unsigned type)
{
return &swap_info[type];
}
+EXPORT_SYMBOL_GPL(get_swap_info_struct);

/*
* swap_lock prevents swap_map being freed. Don't grab an extra
--



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