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Commit 1e01c968 authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk Committed by Linus Torvalds
Browse files

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 703ba7fe (ramster->zcache move]
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: default avatarBob 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 905cd0e1

drivers/staging/zcache/zcache-main.c

+4 −4
Original line number Diff line number Diff line
@@ -1707,9 +1707,9 @@ static struct frontswap_ops zcache_frontswap_ops = { 
	.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 @@ static int __init zcache_init(void) 
			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 @@ static int __init zcache_init(void) 
			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)

drivers/xen/tmem.c

+3 −3
Original line number Diff line number Diff line
@@ -362,7 +362,7 @@ static int __init no_frontswap(char *s) 
}

__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 @@ static int __init xen_tmem_init(void) 
#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);

include/linux/frontswap.h

+1 −1
Original line number Diff line number Diff line
@@ -14,7 +14,7 @@ struct frontswap_ops { 
};



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);

mm/frontswap.c

+18 −20
Original line number Diff line number Diff line
@@ -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 @@ static inline void inc_frontswap_invalidates(void) { } 
 *

 * 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 @@ void __frontswap_init(unsigned type) 
{

	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 @@ int __frontswap_store(struct page *page) 
	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 @@ int __frontswap_store(struct page *page) 
	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 @@ int __frontswap_load(struct page *page) 
	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 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset) 
{

	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 @@ void __frontswap_invalidate_area(unsigned type) 
{

	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));

	}