From: Tim Gardner <tim.gardner@canonical.com>
Date: Sun, 15 Mar 2009 19:38:17 +0000 (-0600)
Subject: UBUNTU: SAUCE: (no-up) swap: Add notify_swap_entry_free callback for compcache
X-Git-Url: http://git.alex.org.uk

UBUNTU: SAUCE: (no-up) swap: Add notify_swap_entry_free callback for compcache

Code is required for ubuntu/compcache

Signed-off-by: Ben Collins <ben.collins@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 4d55932..97a5514 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -185,6 +185,7 @@ struct swap_info_struct {
 	struct block_device *bdev;	/* swap device or bdev of swap file */
 	struct file *swap_file;		/* seldom referenced */
 	unsigned int old_block_size;	/* seldom referenced */
+	void (*notify_swap_entry_free_fn) (unsigned long);
 };
 
 struct swap_list_t {
@@ -344,6 +345,7 @@ extern sector_t swapdev_block(int, pgoff_t);
 extern int reuse_swap_page(struct page *);
 extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
+extern void set_notify_swap_entry_free(unsigned, void (*) (unsigned long));
 
 /* linux/mm/thrash.c */
 extern struct mm_struct *swap_token_mm;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6d6d28c..7c23299 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -594,6 +594,12 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
 			disk->fops->swap_slot_free_notify(p->bdev, offset);
 	}
 
+	if (!swap_count(count)) {
+		mem_cgroup_uncharge_swap(entry);
+			if (p->notify_swap_entry_free_fn)
+				p->notify_swap_entry_free_fn(offset);
+	}
+
 	return usage;
 }
 
@@ -2299,6 +2305,23 @@ int swapcache_prepare(swp_entry_t entry)
 }
 
 /*
+ * Sets callback for event when swap_map[offset] == 0
+ * i.e. page at this swap offset is not longer used.
+ *
+ * type: identifies swap file
+ * fn: callback function
+ */
+void set_notify_swap_entry_free(unsigned type, void (*fn) (unsigned long))
+{
+	struct swap_info_struct *sis;
+	sis = swap_info[type];
+	BUG_ON(!sis);
+	sis->notify_swap_entry_free_fn = fn;
+	return;
+}
+EXPORT_SYMBOL(set_notify_swap_entry_free);
+
+/*
  * swap_lock prevents swap_map being freed. Don't grab an extra
  * reference on the swaphandle, it doesn't matter if it becomes unused.
  */