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>

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>
Konrad Rzeszutek Wilk · Linus Torvalds
1 parent 905cd0e1bf
Showing 4 changed files with 26 additions and 28 deletions Side-by-side Diff
drivers/staging/zcache/zcache-main.c
drivers/xen/tmem.c
include/linux/frontswap.h
mm/frontswap.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)
@@ -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);
@@ -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);
@@ -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));
 	}
...	...	@@ -1707,9 +1707,9 @@
1707	1707	.init = zcache_frontswap_init
1708	1708	};
1709	1709
1710		-struct frontswap_ops zcache_frontswap_register_ops(void)
	1710	+struct frontswap_ops *zcache_frontswap_register_ops(void)
1711	1711	{
1712		- struct frontswap_ops old_ops =
	1712	+ struct frontswap_ops *old_ops =
1713	1713	frontswap_register_ops(&zcache_frontswap_ops);
1714	1714
1715	1715	return old_ops;
...	...	@@ -1874,7 +1874,7 @@
1874	1874	pr_warn("%s: cleancache_ops overridden\n", namestr);
1875	1875	}
1876	1876	if (zcache_enabled && !disable_frontswap) {
1877		- struct frontswap_ops old_ops;
	1877	+ struct frontswap_ops *old_ops;
1878	1878
1879	1879	old_ops = zcache_frontswap_register_ops();
1880	1880	if (frontswap_has_exclusive_gets)
...	...	@@ -1886,7 +1886,7 @@
1886	1886	namestr, frontswap_has_exclusive_gets,
1887	1887	!disable_frontswap_ignore_nonactive);
1888	1888	#endif
1889		- if (old_ops.init != NULL)
	1889	+ if (old_ops != NULL)
1890	1890	pr_warn("%s: frontswap_ops overridden\n", namestr);
1891	1891	}
1892	1892	if (ramster_enabled)
...	...	@@ -362,7 +362,7 @@
362	362	}
363	363	__setup("nofrontswap", no_frontswap);
364	364
365		-static struct frontswap_ops __initdata tmem_frontswap_ops = {
	365	+static struct frontswap_ops tmem_frontswap_ops = {
366	366	.store = tmem_frontswap_store,
367	367	.load = tmem_frontswap_load,
368	368	.invalidate_page = tmem_frontswap_flush_page,
369	369
...	...	@@ -378,11 +378,11 @@
378	378	#ifdef CONFIG_FRONTSWAP
379	379	if (tmem_enabled && use_frontswap) {
380	380	char *s = "";
381		- struct frontswap_ops old_ops =
	381	+ struct frontswap_ops *old_ops =
382	382	frontswap_register_ops(&tmem_frontswap_ops);
383	383
384	384	tmem_frontswap_poolid = -1;
385		- if (old_ops.init != NULL)
	385	+ if (old_ops)
386	386	s = " (WARNING: frontswap_ops overridden)";
387	387	printk(KERN_INFO "frontswap enabled, RAM provided by "
388	388	"Xen Transcendent Memory%s\n", s);
...	...	@@ -14,7 +14,7 @@
14	14	};
15	15
16	16	extern bool frontswap_enabled;
17		-extern struct frontswap_ops
	17	+extern struct frontswap_ops *
18	18	frontswap_register_ops(struct frontswap_ops *ops);
19	19	extern void frontswap_shrink(unsigned long);
20	20	extern unsigned long frontswap_curr_pages(void);
...	...	@@ -24,7 +24,7 @@
24	24	* frontswap_ops is set by frontswap_register_ops to contain the pointers
25	25	* to the frontswap "backend" implementation functions.
26	26	*/
27		-static struct frontswap_ops frontswap_ops __read_mostly;
	27	+static struct frontswap_ops *frontswap_ops __read_mostly;
28	28
29	29	/*
30	30	* This global enablement flag reduces overhead on systems where frontswap_ops
31	31
32	32
33	33
34	34
35	35
36	36
37	37
38	38
...	...	@@ -108,41 +108,39 @@
108	108	*
109	109	* The time between the backend being registered and the swap file system
110	110	* calling the backend (via the frontswap_* functions) is indeterminate as
111		- * backend_registered is not atomic_t (or a value guarded by a spinlock).
	111	+ * frontswap_ops is not atomic_t (or a value guarded by a spinlock).
112	112	* That is OK as we are comfortable missing some of these calls to the newly
113	113	* registered backend.
114	114	*
115	115	* Obviously the opposite (unloading the backend) must be done after all
116	116	* the frontswap_[store\|load\|invalidate_area\|invalidate_page] start
117		- * ignorning or failing the requests - at which point backend_registered
	117	+ * ignorning or failing the requests - at which point frontswap_ops
118	118	* would have to be made in some fashion atomic.
119	119	*/
120	120	static DECLARE_BITMAP(need_init, MAX_SWAPFILES);
121		-static bool backend_registered __read_mostly;
122	121
123	122	/*
124	123	* Register operations for frontswap, returning previous thus allowing
125	124	* detection of multiple backends and possible nesting.
126	125	*/
127		-struct frontswap_ops frontswap_register_ops(struct frontswap_ops *ops)
	126	+struct frontswap_ops frontswap_register_ops(struct frontswap_ops ops)
128	127	{
129		- struct frontswap_ops old = frontswap_ops;
	128	+ struct frontswap_ops *old = frontswap_ops;
130	129	int i;
131	130
132		- frontswap_ops = *ops;
133	131	frontswap_enabled = true;
134	132
135	133	for (i = 0; i < MAX_SWAPFILES; i++) {
136	134	if (test_and_clear_bit(i, need_init))
137		- (*frontswap_ops.init)(i);
	135	+ ops->init(i);
138	136	}
139	137	/*
140		- * We MUST have backend_registered set _after_ the frontswap_init's
	138	+ * We MUST have frontswap_ops set _after_ the frontswap_init's
141	139	* have been called. Otherwise __frontswap_store might fail. Hence
142	140	* the barrier to make sure compiler does not re-order us.
143	141	*/
144	142	barrier();
145		- backend_registered = true;
	143	+ frontswap_ops = ops;
146	144	return old;
147	145	}
148	146	EXPORT_SYMBOL(frontswap_register_ops);
149	147
...	...	@@ -172,11 +170,11 @@
172	170	{
173	171	struct swap_info_struct *sis = swap_info[type];
174	172
175		- if (backend_registered) {
	173	+ if (frontswap_ops) {
176	174	BUG_ON(sis == NULL);
177	175	if (sis->frontswap_map == NULL)
178	176	return;
179		- (*frontswap_ops.init)(type);
	177	+ frontswap_ops->init(type);
180	178	} else {
181	179	BUG_ON(type > MAX_SWAPFILES);
182	180	set_bit(type, need_init);
...	...	@@ -206,7 +204,7 @@
206	204	struct swap_info_struct *sis = swap_info[type];
207	205	pgoff_t offset = swp_offset(entry);
208	206
209		- if (!backend_registered) {
	207	+ if (!frontswap_ops) {
210	208	inc_frontswap_failed_stores();
211	209	return ret;
212	210	}
...	...	@@ -215,7 +213,7 @@
215	213	BUG_ON(sis == NULL);
216	214	if (frontswap_test(sis, offset))
217	215	dup = 1;
218		- ret = frontswap_ops.store(type, offset, page);
	216	+ ret = frontswap_ops->store(type, offset, page);
219	217	if (ret == 0) {
220	218	frontswap_set(sis, offset);
221	219	inc_frontswap_succ_stores();
222	220
...	...	@@ -250,13 +248,13 @@
250	248	struct swap_info_struct *sis = swap_info[type];
251	249	pgoff_t offset = swp_offset(entry);
252	250
253		- if (!backend_registered)
	251	+ if (!frontswap_ops)
254	252	return ret;
255	253
256	254	BUG_ON(!PageLocked(page));
257	255	BUG_ON(sis == NULL);
258	256	if (frontswap_test(sis, offset))
259		- ret = frontswap_ops.load(type, offset, page);
	257	+ ret = frontswap_ops->load(type, offset, page);
260	258	if (ret == 0) {
261	259	inc_frontswap_loads();
262	260	if (frontswap_tmem_exclusive_gets_enabled) {
263	261
...	...	@@ -276,12 +274,12 @@
276	274	{
277	275	struct swap_info_struct *sis = swap_info[type];
278	276
279		- if (!backend_registered)
	277	+ if (!frontswap_ops)
280	278	return;
281	279
282	280	BUG_ON(sis == NULL);
283	281	if (frontswap_test(sis, offset)) {
284		- frontswap_ops.invalidate_page(type, offset);
	282	+ frontswap_ops->invalidate_page(type, offset);
285	283	__frontswap_clear(sis, offset);
286	284	inc_frontswap_invalidates();
287	285	}
288	286
...	...	@@ -296,11 +294,11 @@
296	294	{
297	295	struct swap_info_struct *sis = swap_info[type];
298	296
299		- if (backend_registered) {
	297	+ if (frontswap_ops) {
300	298	BUG_ON(sis == NULL);
301	299	if (sis->frontswap_map == NULL)
302	300	return;
303		- (*frontswap_ops.invalidate_area)(type);
	301	+ frontswap_ops->invalidate_area(type);
304	302	atomic_set(&sis->frontswap_pages, 0);
305	303	memset(sis->frontswap_map, 0, sis->max / sizeof(long));
306	304	}