mm: introduce migrate_replace_page() for migrating page to the given target

introduce migrate_replace_page for migrating
page to the given target

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

bug 1517584

Change-Id: I5f1d3bcb19ca7d9c9cf7234e8d3472a42c4f40af
Signed-off-by: Vandana Salve <vsalve@nvidia.com>
Reviewed-on: http://git-master/r/421675
Reviewed-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index a88c12f2235d..316b0ade86da 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1084,6 +1084,65 @@ out:
 	return rc;
 }
 
+/*
+ * migrate_replace_page
+ *
+ * The function takes one single page and a target page (newpage) and
+ * tries to migrate data to the target page. The caller must ensure that
+ * the source page is locked with one additional get_page() call, which
+ * will be freed during the migration. The caller also must release newpage
+ * if migration fails, otherwise the ownership of the newpage is taken.
+ * Source page is released if migration succeeds.
+ *
+ * Return: error code or 0 on success.
+ */
+int migrate_replace_page(struct page *page, struct page *newpage)
+{
+	struct zone *zone = page_zone(page);
+	unsigned long flags;
+	int ret = -EAGAIN;
+	int pass;
+
+	migrate_prep();
+
+	spin_lock_irqsave(&zone->lru_lock, flags);
+
+	if (PageLRU(page) &&
+	    __isolate_lru_page(page, ISOLATE_UNEVICTABLE) == 0) {
+		struct lruvec *lruvec = mem_cgroup_page_lruvec(page, zone);
+		del_page_from_lru_list(page, lruvec, page_lru(page));
+		spin_unlock_irqrestore(&zone->lru_lock, flags);
+	} else {
+		spin_unlock_irqrestore(&zone->lru_lock, flags);
+		return -EAGAIN;
+	}
+
+	/* page is now isolated, so release additional reference */
+	put_page(page);
+
+	for (pass = 0; pass < 10 && ret != 0; pass++) {
+		cond_resched();
+
+		if (page_count(page) == 1) {
+			/* page was freed from under us, so we are done */
+			ret = 0;
+			break;
+		}
+		ret = __unmap_and_move(page, newpage, 1, MIGRATE_SYNC);
+	}
+
+	if (ret == 0) {
+		/* take ownership of newpage and add it to lru */
+		putback_lru_page(newpage);
+	} else {
+		/* restore additional reference to the oldpage */
+		get_page(page);
+	}
+
+	putback_lru_page(page);
+	return ret;
+}
+
 #ifdef CONFIG_NUMA
 /*
  * Move a list of individual pages