Merge tag 'stable/for-linus-3.6-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/mm

Pull frontswap updates from Konrad Rzeszutek Wilk:
 "Cleanups in code and documentation.  Little bit of refactoring for
  cleaner look."

* tag 'stable/for-linus-3.6-rc0-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/mm:
  mm/frontswap: cleanup doc and comment error
  mm: frontswap: remove unneeded headers
  mm: frontswap: split out function to clear a page out
  mm: frontswap: remove unnecessary check during initialization
  mm: frontswap: make all branches of if statement in put page consistent
  mm: frontswap: split frontswap_shrink further to simplify locking
  mm: frontswap: split out __frontswap_unuse_pages
  mm: frontswap: split out __frontswap_curr_pages
  mm: frontswap: trivial coding convention issues
  mm: frontswap: remove casting from function calls through ops structure

1 files changed, 90 insertions, 60 deletions

diff --git a/mm/frontswap.c b/mm/frontswap.c
index e25025574a02..6b3e71a2cd48 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -11,15 +11,11 @@
  * This work is licensed under the terms of the GNU GPL, version 2.
  */
 
-#include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/swap.h>
 #include <linux/swapops.h>
-#include <linux/proc_fs.h>
 #include <linux/security.h>
-#include <linux/capability.h>
 #include <linux/module.h>
-#include <linux/uaccess.h>
 #include <linux/debugfs.h>
 #include <linux/frontswap.h>
 #include <linux/swapfile.h>
@@ -110,16 +106,21 @@ void __frontswap_init(unsigned type)
 	BUG_ON(sis == NULL);
 	if (sis->frontswap_map == NULL)
 		return;
-	if (frontswap_enabled)
-		(*frontswap_ops.init)(type);
+	frontswap_ops.init(type);
 }
 EXPORT_SYMBOL(__frontswap_init);
 
+static inline void __frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
+{
+	frontswap_clear(sis, offset);
+	atomic_dec(&sis->frontswap_pages);
+}
+
 /*
  * "Store" data from a page to frontswap and associate it with the page's
  * swaptype and offset.  Page must be locked and in the swap cache.
  * If frontswap already contains a page with matching swaptype and
- * offset, the frontswap implmentation may either overwrite the data and
+ * offset, the frontswap implementation may either overwrite the data and
  * return success or invalidate the page from frontswap and return failure.
  */
 int __frontswap_store(struct page *page)
@@ -134,22 +135,21 @@ 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();
 		if (!dup)
 			atomic_inc(&sis->frontswap_pages);
-	} else if (dup) {
+	} else {
 		/*
 		  failed dup always results in automatic invalidate of
 		  the (older) page from frontswap
 		 */
-		frontswap_clear(sis, offset);
-		atomic_dec(&sis->frontswap_pages);
-		inc_frontswap_failed_stores();
-	} else
 		inc_frontswap_failed_stores();
+		if (dup)
+			__frontswap_clear(sis, offset);
+	}
 	if (frontswap_writethrough_enabled)
 		/* report failure so swap also writes to swap device */
 		ret = -1;
@@ -173,7 +173,7 @@ int __frontswap_load(struct page *page)
 	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();
 	return ret;
@@ -190,9 +190,8 @@ void __frontswap_invalidate_page(unsigned type, pgoff_t offset)
 
 	BUG_ON(sis == NULL);
 	if (frontswap_test(sis, offset)) {
-		(*frontswap_ops.invalidate_page)(type, offset);
-		atomic_dec(&sis->frontswap_pages);
-		frontswap_clear(sis, offset);
+		frontswap_ops.invalidate_page(type, offset);
+		__frontswap_clear(sis, offset);
 		inc_frontswap_invalidates();
 	}
 }
@@ -209,67 +208,102 @@ void __frontswap_invalidate_area(unsigned type)
 	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));
 }
 EXPORT_SYMBOL(__frontswap_invalidate_area);
 
-/*
- * Frontswap, like a true swap device, may unnecessarily retain pages
- * under certain circumstances; "shrink" frontswap is essentially a
- * "partial swapoff" and works by calling try_to_unuse to attempt to
- * unuse enough frontswap pages to attempt to -- subject to memory
- * constraints -- reduce the number of pages in frontswap to the
- * number given in the parameter target_pages.
- */
-void frontswap_shrink(unsigned long target_pages)
+static unsigned long __frontswap_curr_pages(void)
 {
-	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;
-	bool locked = false;
+	unsigned long totalpages = 0;
+	struct swap_info_struct *si = NULL;
 
-	/*
-	 * we don't want to hold swap_lock while doing a very
-	 * lengthy try_to_unuse, but swap_list may change
-	 * so restart scan from swap_list.head each time
-	 */
-	spin_lock(&swap_lock);
-	locked = true;
-	total_pages = 0;
+	assert_spin_locked(&swap_lock);
 	for (type = swap_list.head; type >= 0; type = si->next) {
 		si = swap_info[type];
-		total_pages += atomic_read(&si->frontswap_pages);
+		totalpages += atomic_read(&si->frontswap_pages);
 	}
-	if (total_pages <= target_pages)
-		goto out;
-	total_pages_to_unuse = total_pages - target_pages;
+	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)
+		if (total_pages_to_unuse < si_frontswap_pages) {
 			pages = pages_to_unuse = total_pages_to_unuse;
-		else {
+		} 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))
+		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;
 	}
-	if (type < 0)
-		goto out;
-	locked = false;
+
+	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
+ * "partial swapoff" and works by calling try_to_unuse to attempt to
+ * unuse enough frontswap pages to attempt to -- subject to memory
+ * constraints -- reduce the number of pages in frontswap to the
+ * number given in the parameter target_pages.
+ */
+void frontswap_shrink(unsigned long target_pages)
+{
+	unsigned long pages_to_unuse = 0;
+	int type, ret;
+
+	/*
+	 * we don't want to hold swap_lock while doing a very
+	 * lengthy try_to_unuse, but swap_list may change
+	 * so restart scan from swap_list.head each time
+	 */
+	spin_lock(&swap_lock);
+	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);
@@ -281,16 +315,12 @@ EXPORT_SYMBOL(frontswap_shrink);
  */
 unsigned long frontswap_curr_pages(void)
 {
-	int type;
 	unsigned long totalpages = 0;
-	struct swap_info_struct *si = NULL;
 
 	spin_lock(&swap_lock);
-	for (type = swap_list.head; type >= 0; type = si->next) {
-		si = swap_info[type];
-		totalpages += atomic_read(&si->frontswap_pages);
-	}
+	totalpages = __frontswap_curr_pages();
 	spin_unlock(&swap_lock);
+
 	return totalpages;
 }
 EXPORT_SYMBOL(frontswap_curr_pages);