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/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index e23d814..09c69c8 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1707,9 +1707,9 @@
.init = zcache_frontswap_init
};
-struct frontswap_ops zcache_frontswap_register_ops(void)
+struct frontswap_ops *zcache_frontswap_register_ops(void)
{
- struct frontswap_ops old_ops =
+ struct frontswap_ops *old_ops =
frontswap_register_ops(&zcache_frontswap_ops);
return old_ops;
@@ -1874,7 +1874,7 @@
pr_warn("%s: cleancache_ops overridden\n", namestr);
}
if (zcache_enabled && !disable_frontswap) {
- struct frontswap_ops old_ops;
+ struct frontswap_ops *old_ops;
old_ops = zcache_frontswap_register_ops();
if (frontswap_has_exclusive_gets)
@@ -1886,7 +1886,7 @@
namestr, frontswap_has_exclusive_gets,
!disable_frontswap_ignore_nonactive);
#endif
- if (old_ops.init != NULL)
+ if (old_ops != NULL)
pr_warn("%s: frontswap_ops overridden\n", namestr);
}
if (ramster_enabled)
diff --git a/drivers/xen/tmem.c b/drivers/xen/tmem.c
index 3ee836d..7a01a5f 100644
--- a/drivers/xen/tmem.c
+++ b/drivers/xen/tmem.c
@@ -362,7 +362,7 @@
}
__setup("nofrontswap", no_frontswap);
-static struct frontswap_ops __initdata tmem_frontswap_ops = {
+static struct frontswap_ops tmem_frontswap_ops = {
.store = tmem_frontswap_store,
.load = tmem_frontswap_load,
.invalidate_page = tmem_frontswap_flush_page,
@@ -378,11 +378,11 @@
#ifdef CONFIG_FRONTSWAP
if (tmem_enabled && use_frontswap) {
char *s = "";
- struct frontswap_ops old_ops =
+ struct frontswap_ops *old_ops =
frontswap_register_ops(&tmem_frontswap_ops);
tmem_frontswap_poolid = -1;
- if (old_ops.init != NULL)
+ if (old_ops)
s = " (WARNING: frontswap_ops overridden)";
printk(KERN_INFO "frontswap enabled, RAM provided by "
"Xen Transcendent Memory%s\n", s);
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
index 3044254..d4f2987 100644
--- a/include/linux/frontswap.h
+++ b/include/linux/frontswap.h
@@ -14,7 +14,7 @@
};
extern bool frontswap_enabled;
-extern struct frontswap_ops
+extern struct frontswap_ops *
frontswap_register_ops(struct frontswap_ops *ops);
extern void frontswap_shrink(unsigned long);
extern unsigned long frontswap_curr_pages(void);
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));
}