frontswap: make frontswap_init use a pointer for the ops
This simplifies the code in the frontswap - we can get rid of the
'backend_registered' test and instead check against frontswap_ops.
[v1: Rebase on top of 703ba7fe5e0 (ramster->zcache move]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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: 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 cbd2b8a..e44c9cb 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -24,7 +24,7 @@
* frontswap_ops is set by frontswap_register_ops to contain the pointers
* to the frontswap "backend" implementation functions.
*/
-static struct frontswap_ops frontswap_ops __read_mostly;
+static struct frontswap_ops *frontswap_ops __read_mostly;
/*
* This global enablement flag reduces overhead on systems where frontswap_ops
@@ -108,41 +108,39 @@
*
* The time between the backend being registered and the swap file system
* calling the backend (via the frontswap_* functions) is indeterminate as
- * backend_registered is not atomic_t (or a value guarded by a spinlock).
+ * frontswap_ops is not atomic_t (or a value guarded by a spinlock).
* That is OK as we are comfortable missing some of these calls to the newly
* registered backend.
*
* Obviously the opposite (unloading the backend) must be done after all
* the frontswap_[store|load|invalidate_area|invalidate_page] start
- * ignorning or failing the requests - at which point backend_registered
+ * ignorning or failing the requests - at which point frontswap_ops
* would have to be made in some fashion atomic.
*/
static DECLARE_BITMAP(need_init, MAX_SWAPFILES);
-static bool backend_registered __read_mostly;
/*
* Register operations for frontswap, returning previous thus allowing
* detection of multiple backends and possible nesting.
*/
-struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
+struct frontswap_ops *frontswap_register_ops(struct frontswap_ops *ops)
{
- struct frontswap_ops old = frontswap_ops;
+ struct frontswap_ops *old = frontswap_ops;
int i;
- frontswap_ops = *ops;
frontswap_enabled = true;
for (i = 0; i < MAX_SWAPFILES; i++) {
if (test_and_clear_bit(i, need_init))
- (*frontswap_ops.init)(i);
+ ops->init(i);
}
/*
- * We MUST have backend_registered set _after_ the frontswap_init's
+ * We MUST have frontswap_ops set _after_ the frontswap_init's
* have been called. Otherwise __frontswap_store might fail. Hence
* the barrier to make sure compiler does not re-order us.
*/
barrier();
- backend_registered = true;
+ frontswap_ops = ops;
return old;
}
EXPORT_SYMBOL(frontswap_register_ops);
@@ -172,11 +170,11 @@
{
struct swap_info_struct *sis = swap_info[type];
- if (backend_registered) {
+ if (frontswap_ops) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
- (*frontswap_ops.init)(type);
+ frontswap_ops->init(type);
} else {
BUG_ON(type > MAX_SWAPFILES);
set_bit(type, need_init);
@@ -206,7 +204,7 @@
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!backend_registered) {
+ if (!frontswap_ops) {
inc_frontswap_failed_stores();
return ret;
}
@@ -215,7 +213,7 @@
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
dup = 1;
- ret = frontswap_ops.store(type, offset, page);
+ ret = frontswap_ops->store(type, offset, page);
if (ret == 0) {
frontswap_set(sis, offset);
inc_frontswap_succ_stores();
@@ -250,13 +248,13 @@
struct swap_info_struct *sis = swap_info[type];
pgoff_t offset = swp_offset(entry);
- if (!backend_registered)
+ if (!frontswap_ops)
return ret;
BUG_ON(!PageLocked(page));
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset))
- ret = frontswap_ops.load(type, offset, page);
+ ret = frontswap_ops->load(type, offset, page);
if (ret == 0) {
inc_frontswap_loads();
if (frontswap_tmem_exclusive_gets_enabled) {
@@ -276,12 +274,12 @@
{
struct swap_info_struct *sis = swap_info[type];
- if (!backend_registered)
+ if (!frontswap_ops)
return;
BUG_ON(sis == NULL);
if (frontswap_test(sis, offset)) {
- frontswap_ops.invalidate_page(type, offset);
+ frontswap_ops->invalidate_page(type, offset);
__frontswap_clear(sis, offset);
inc_frontswap_invalidates();
}
@@ -296,11 +294,11 @@
{
struct swap_info_struct *sis = swap_info[type];
- if (backend_registered) {
+ if (frontswap_ops) {
BUG_ON(sis == NULL);
if (sis->frontswap_map == NULL)
return;
- (*frontswap_ops.invalidate_area)(type);
+ frontswap_ops->invalidate_area(type);
atomic_set(&sis->frontswap_pages, 0);
memset(sis->frontswap_map, 0, sis->max / sizeof(long));
}