mm: frontswap: split out __frontswap_unuse_pages

An attempt at making frontswap_shrink shorter and more readable. This patch splits out walking through the swap list to find an entry with enough pages to unuse. Also, assert that the internal __frontswap_unuse_pages is called under swap lock, since that part of code was previously directly happen inside the lock. Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

mm: frontswap: split out __frontswap_unuse_pages
An attempt at making frontswap_shrink shorter and more readable. This patch splits out walking through the swap list to find an entry with enough pages to unuse. Also, assert that the internal __frontswap_unuse_pages is called under swap lock, since that part of code was previously directly happen inside the lock. 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 96253444db
Showing 1 changed file with 39 additions and 20 deletions Side-by-side Diff
mm/frontswap.c
@@ -230,6 +230,41 @@
 	return totalpages;
 }
  
+static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
+					int *swapid)
+{
+	int ret = -EINVAL;
+	struct swap_info_struct *si = NULL;
+	int si_frontswap_pages;
+	unsigned long total_pages_to_unuse = total;
+	unsigned long pages = 0, pages_to_unuse = 0;
+	int type;
+
+	assert_spin_locked(&swap_lock);
+	for (type = swap_list.head; type >= 0; type = si->next) {
+		si = swap_info[type];
+		si_frontswap_pages = atomic_read(&si->frontswap_pages);
+		if (total_pages_to_unuse < si_frontswap_pages) {
+			pages = pages_to_unuse = total_pages_to_unuse;
+		} else {
+			pages = si_frontswap_pages;
+			pages_to_unuse = 0; /* unuse all */
+		}
+		/* ensure there is enough RAM to fetch pages from frontswap */
+		if (security_vm_enough_memory_mm(current->mm, pages)) {
+			ret = -ENOMEM;
+			continue;
+		}
+		vm_unacct_memory(pages);
+		*unused = pages_to_unuse;
+		*swapid = type;
+		ret = 0;
+		break;
+	}
+
+	return ret;
+}
+
 /*
  * Frontswap, like a true swap device, may unnecessarily retain pages
  * under certain circumstances; "shrink" frontswap is essentially a
  
@@ -240,11 +275,9 @@
  */
 void frontswap_shrink(unsigned long target_pages)
 {
-	struct swap_info_struct *si = NULL;
-	int si_frontswap_pages;
 	unsigned long total_pages = 0, total_pages_to_unuse;
-	unsigned long pages = 0, pages_to_unuse = 0;
-	int type;
+	unsigned long pages_to_unuse = 0;
+	int type, ret;
 	bool locked = false;
  
 	/*
@@ -258,22 +291,8 @@
 	if (total_pages <= target_pages)
 		goto out;
 	total_pages_to_unuse = total_pages - target_pages;
-	for (type = swap_list.head; type >= 0; type = si->next) {
-		si = swap_info[type];
-		si_frontswap_pages = atomic_read(&si->frontswap_pages);
-		if (total_pages_to_unuse < si_frontswap_pages) {
-			pages = pages_to_unuse = total_pages_to_unuse;
-		} else {
-			pages = si_frontswap_pages;
-			pages_to_unuse = 0; /* unuse all */
-		}
-		/* ensure there is enough RAM to fetch pages from frontswap */
-		if (security_vm_enough_memory_mm(current->mm, pages))
-			continue;
-		vm_unacct_memory(pages);
-		break;
-	}
-	if (type < 0)
+	ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
+	if (ret < 0)
 		goto out;
 	locked = false;
 	spin_unlock(&swap_lock);
...	...	@@ -230,6 +230,41 @@
230	230	return totalpages;
231	231	}
232	232
	233	+static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
	234	+ int *swapid)
	235	+{
	236	+ int ret = -EINVAL;
	237	+ struct swap_info_struct *si = NULL;
	238	+ int si_frontswap_pages;
	239	+ unsigned long total_pages_to_unuse = total;
	240	+ unsigned long pages = 0, pages_to_unuse = 0;
	241	+ int type;
	242	+
	243	+ assert_spin_locked(&swap_lock);
	244	+ for (type = swap_list.head; type >= 0; type = si->next) {
	245	+ si = swap_info[type];
	246	+ si_frontswap_pages = atomic_read(&si->frontswap_pages);
	247	+ if (total_pages_to_unuse < si_frontswap_pages) {
	248	+ pages = pages_to_unuse = total_pages_to_unuse;
	249	+ } else {
	250	+ pages = si_frontswap_pages;
	251	+ pages_to_unuse = 0; /* unuse all */
	252	+ }
	253	+ /* ensure there is enough RAM to fetch pages from frontswap */
	254	+ if (security_vm_enough_memory_mm(current->mm, pages)) {
	255	+ ret = -ENOMEM;
	256	+ continue;
	257	+ }
	258	+ vm_unacct_memory(pages);
	259	+ *unused = pages_to_unuse;
	260	+ *swapid = type;
	261	+ ret = 0;
	262	+ break;
	263	+ }
	264	+
	265	+ return ret;
	266	+}
	267	+
233	268	/*
234	269	* Frontswap, like a true swap device, may unnecessarily retain pages
235	270	* under certain circumstances; "shrink" frontswap is essentially a
236	271
...	...	@@ -240,11 +275,9 @@
240	275	*/
241	276	void frontswap_shrink(unsigned long target_pages)
242	277	{
243		- struct swap_info_struct *si = NULL;
244		- int si_frontswap_pages;
245	278	unsigned long total_pages = 0, total_pages_to_unuse;
246		- unsigned long pages = 0, pages_to_unuse = 0;
247		- int type;
	279	+ unsigned long pages_to_unuse = 0;
	280	+ int type, ret;
248	281	bool locked = false;
249	282
250	283	/*
...	...	@@ -258,22 +291,8 @@
258	291	if (total_pages <= target_pages)
259	292	goto out;
260	293	total_pages_to_unuse = total_pages - target_pages;
261		- for (type = swap_list.head; type >= 0; type = si->next) {
262		- si = swap_info[type];
263		- si_frontswap_pages = atomic_read(&si->frontswap_pages);
264		- if (total_pages_to_unuse < si_frontswap_pages) {
265		- pages = pages_to_unuse = total_pages_to_unuse;
266		- } else {
267		- pages = si_frontswap_pages;
268		- pages_to_unuse = 0; /* unuse all */
269		- }
270		- /* ensure there is enough RAM to fetch pages from frontswap */
271		- if (security_vm_enough_memory_mm(current->mm, pages))
272		- continue;
273		- vm_unacct_memory(pages);
274		- break;
275		- }
276		- if (type < 0)
	294	+ ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
	295	+ if (ret < 0)
277	296	goto out;
278	297	locked = false;
279	298	spin_unlock(&swap_lock);