mm: frontswap: split frontswap_shrink further to simplify locking

Split frontswap_shrink to simplify the locking in the original code. Also, assert that the function that was split still runs under the swap spinlock. Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

mm: frontswap: split frontswap_shrink further to simplify locking
Split frontswap_shrink to simplify the locking in the original code. Also, assert that the function that was split still runs under the swap spinlock. Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Sasha Levin · Konrad Rzeszutek Wilk
1 parent f116695a50
Showing 1 changed file with 21 additions and 15 deletions Side-by-side Diff
mm/frontswap.c
@@ -265,6 +265,24 @@
 	return ret;
 }
  
+static int __frontswap_shrink(unsigned long target_pages,
+				unsigned long *pages_to_unuse,
+				int *type)
+{
+	unsigned long total_pages = 0, total_pages_to_unuse;
+
+	assert_spin_locked(&swap_lock);
+
+	total_pages = __frontswap_curr_pages();
+	if (total_pages <= target_pages) {
+		/* Nothing to do */
+		*pages_to_unuse = 0;
+		return 0;
+	}
+	total_pages_to_unuse = total_pages - target_pages;
+	return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
+}
+
 /*
  * Frontswap, like a true swap device, may unnecessarily retain pages
  * under certain circumstances; "shrink" frontswap is essentially a
  
@@ -275,10 +293,8 @@
  */
 void frontswap_shrink(unsigned long target_pages)
 {
-	unsigned long total_pages = 0, total_pages_to_unuse;
 	unsigned long pages_to_unuse = 0;
 	int type, ret;
-	bool locked = false;
  
 	/*
 	 * we don't want to hold swap_lock while doing a very
  
@@ -286,20 +302,10 @@
 	 * so restart scan from swap_list.head each time
 	 */
 	spin_lock(&swap_lock);
-	locked = true;
-	total_pages = __frontswap_curr_pages();
-	if (total_pages <= target_pages)
-		goto out;
-	total_pages_to_unuse = total_pages - target_pages;
-	ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
-	if (ret < 0)
-		goto out;
-	locked = false;
+	ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
 	spin_unlock(&swap_lock);
-	try_to_unuse(type, true, pages_to_unuse);
-out:
-	if (locked)
-		spin_unlock(&swap_lock);
+	if (ret == 0 && pages_to_unuse)
+		try_to_unuse(type, true, pages_to_unuse);
 	return;
 }
 EXPORT_SYMBOL(frontswap_shrink);
...	...	@@ -265,6 +265,24 @@
265	265	return ret;
266	266	}
267	267
	268	+static int __frontswap_shrink(unsigned long target_pages,
	269	+ unsigned long *pages_to_unuse,
	270	+ int *type)
	271	+{
	272	+ unsigned long total_pages = 0, total_pages_to_unuse;
	273	+
	274	+ assert_spin_locked(&swap_lock);
	275	+
	276	+ total_pages = __frontswap_curr_pages();
	277	+ if (total_pages <= target_pages) {
	278	+ /* Nothing to do */
	279	+ *pages_to_unuse = 0;
	280	+ return 0;
	281	+ }
	282	+ total_pages_to_unuse = total_pages - target_pages;
	283	+ return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
	284	+}
	285	+
268	286	/*
269	287	* Frontswap, like a true swap device, may unnecessarily retain pages
270	288	* under certain circumstances; "shrink" frontswap is essentially a
271	289
...	...	@@ -275,10 +293,8 @@
275	293	*/
276	294	void frontswap_shrink(unsigned long target_pages)
277	295	{
278		- unsigned long total_pages = 0, total_pages_to_unuse;
279	296	unsigned long pages_to_unuse = 0;
280	297	int type, ret;
281		- bool locked = false;
282	298
283	299	/*
284	300	* we don't want to hold swap_lock while doing a very
285	301
...	...	@@ -286,20 +302,10 @@
286	302	* so restart scan from swap_list.head each time
287	303	*/
288	304	spin_lock(&swap_lock);
289		- locked = true;
290		- total_pages = __frontswap_curr_pages();
291		- if (total_pages <= target_pages)
292		- goto out;
293		- total_pages_to_unuse = total_pages - target_pages;
294		- ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
295		- if (ret < 0)
296		- goto out;
297		- locked = false;
	305	+ ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
298	306	spin_unlock(&swap_lock);
299		- try_to_unuse(type, true, pages_to_unuse);
300		-out:
301		- if (locked)
302		- spin_unlock(&swap_lock);
	307	+ if (ret == 0 && pages_to_unuse)
	308	+ try_to_unuse(type, true, pages_to_unuse);
303	309	return;
304	310	}
305	311	EXPORT_SYMBOL(frontswap_shrink);