mm: frontswap: cleanup code

After allowing tmem backends to build/run as modules, frontswap_enabled
always true if defined CONFIG_FRONTSWAP.  But frontswap_test() depends on
whether backend is registered, mv it into frontswap.c using fronstswap_ops
to make the decision.

frontswap_set/clear are not used outside frontswap, so don't export them.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andor Daam <andor.daam@googlemail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index d4f29875c7cc407281f57e60d6fcf5d3b8790038..6c49e1eba5525a28a4bbec9392297d30dda8ae67 100644 (file)
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -22,6 +22,7 @@ extern void frontswap_writethrough(bool);
 #define FRONTSWAP_HAS_EXCLUSIVE_GETS
 extern void frontswap_tmem_exclusive_gets(bool);
 
+extern bool __frontswap_test(struct swap_info_struct *, pgoff_t);
 extern void __frontswap_init(unsigned type);
 extern int __frontswap_store(struct page *page);
 extern int __frontswap_load(struct page *page);
@@ -29,26 +30,11 @@ extern void __frontswap_invalidate_page(unsigned, pgoff_t);
 extern void __frontswap_invalidate_area(unsigned);
 
 #ifdef CONFIG_FRONTSWAP
+#define frontswap_enabled (1)
 
 static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
 {
-       bool ret = false;
-
-       if (frontswap_enabled && sis->frontswap_map)
-               ret = test_bit(offset, sis->frontswap_map);
-       return ret;
-}
-
-static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset)
-{
-       if (frontswap_enabled && sis->frontswap_map)
-               set_bit(offset, sis->frontswap_map);
-}
-
-static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
-{
-       if (frontswap_enabled && sis->frontswap_map)
-               clear_bit(offset, sis->frontswap_map);
+       return __frontswap_test(sis, offset);
 }
 
 static inline void frontswap_map_set(struct swap_info_struct *p,
@@ -71,14 +57,6 @@ static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
        return false;
 }
 
-static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset)
-{
-}
-
-static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
-{
-}
-
 static inline void frontswap_map_set(struct swap_info_struct *p,
                                     unsigned long *map)
 {

diff --git a/mm/frontswap.c b/mm/frontswap.c
index e44c9cbd1443b836b395ccad6f72078b3bcaeb0e..2760b0f98822af7f734e7beb9398ac4e023cb1fb 100644 (file)
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -26,14 +26,6 @@
  */
 static struct frontswap_ops *frontswap_ops __read_mostly;
 
-/*
- * This global enablement flag reduces overhead on systems where frontswap_ops
- * has not been registered, so is preferred to the slower alternative: a
- * function call that checks a non-global.
- */
-bool frontswap_enabled __read_mostly;
-EXPORT_SYMBOL(frontswap_enabled);
-
 /*
  * If enabled, frontswap_store will return failure even on success.  As
  * a result, the swap subsystem will always write the page to swap, in
@@ -128,8 +120,6 @@ struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
        struct frontswap_ops *old = frontswap_ops;
        int i;
 
-       frontswap_enabled = true;
-
        for (i = 0; i < MAX_SWAPFILES; i++) {
                if (test_and_clear_bit(i, need_init))
                        ops->init(i);
@@ -183,9 +173,21 @@ void __frontswap_init(unsigned type)
 }
 EXPORT_SYMBOL(__frontswap_init);
 
-static inline void __frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
+bool __frontswap_test(struct swap_info_struct *sis,
+                               pgoff_t offset)
+{
+       bool ret = false;
+
+       if (frontswap_ops && sis->frontswap_map)
+               ret = test_bit(offset, sis->frontswap_map);
+       return ret;
+}
+EXPORT_SYMBOL(__frontswap_test);
+
+static inline void __frontswap_clear(struct swap_info_struct *sis,
+                               pgoff_t offset)
 {
-       frontswap_clear(sis, offset);
+       clear_bit(offset, sis->frontswap_map);
        atomic_dec(&sis->frontswap_pages);
 }
 
@@ -204,18 +206,20 @@ int __frontswap_store(struct page *page)
        struct swap_info_struct *sis = swap_info[type];
        pgoff_t offset = swp_offset(entry);
 
-       if (!frontswap_ops) {
-               inc_frontswap_failed_stores();
+       /*
+        * Return if no backend registed.
+        * Don't need to inc frontswap_failed_stores here.
+        */
+       if (!frontswap_ops)
                return ret;
-       }
 
        BUG_ON(!PageLocked(page));
        BUG_ON(sis == NULL);
-       if (frontswap_test(sis, offset))
+       if (__frontswap_test(sis, offset))
                dup = 1;
        ret = frontswap_ops->store(type, offset, page);
        if (ret == 0) {
-               frontswap_set(sis, offset);
+               set_bit(offset, sis->frontswap_map);
                inc_frontswap_succ_stores();
                if (!dup)
                        atomic_inc(&sis->frontswap_pages);
@@ -248,18 +252,18 @@ int __frontswap_load(struct page *page)
        struct swap_info_struct *sis = swap_info[type];
        pgoff_t offset = swp_offset(entry);
 
-       if (!frontswap_ops)
-               return ret;
-
        BUG_ON(!PageLocked(page));
        BUG_ON(sis == NULL);
-       if (frontswap_test(sis, offset))
+       /*
+        * __frontswap_test() will check whether there is backend registered
+        */
+       if (__frontswap_test(sis, offset))
                ret = frontswap_ops->load(type, offset, page);
        if (ret == 0) {
                inc_frontswap_loads();
                if (frontswap_tmem_exclusive_gets_enabled) {
                        SetPageDirty(page);
-                       frontswap_clear(sis, offset);
+                       __frontswap_clear(sis, offset);
                }
        }
        return ret;
@@ -274,11 +278,11 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
 {
        struct swap_info_struct *sis = swap_info[type];
 
-       if (!frontswap_ops)
-               return;
-
        BUG_ON(sis == NULL);
-       if (frontswap_test(sis, offset)) {
+       /*
+        * __frontswap_test() will check whether there is backend registered
+        */
+       if (__frontswap_test(sis, offset)) {
                frontswap_ops->invalidate_page(type, offset);
                __frontswap_clear(sis, offset);
                inc_frontswap_invalidates();
@@ -435,7 +439,6 @@ static int __init init_frontswap(void)
        debugfs_create_u64("invalidates", S_IRUGO,
                                root, &frontswap_invalidates);
 #endif
-       frontswap_enabled = 1;
        return 0;
 }