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/mm/frontswap.c b/mm/frontswap.c
index e44c9cb..2760b0f 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -27,14 +27,6 @@
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
* effect converting frontswap into a writethrough cache. In this mode,
@@ -128,8 +120,6 @@
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 @@
}
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)
{
- frontswap_clear(sis, 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)
+{
+ clear_bit(offset, sis->frontswap_map);
atomic_dec(&sis->frontswap_pages);
}
@@ -204,18 +206,20 @@
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 @@
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 @@
{
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 @@
debugfs_create_u64("invalidates", S_IRUGO,
root, &frontswap_invalidates);
#endif
- frontswap_enabled = 1;
return 0;
}