From d0c338ed0e5d3d57a95b677113bae2e36b5efe3e Mon Sep 17 00:00:00 2001
From: Shaohua Li <shaohua.li@intel.com>
Date: Mon, 4 Feb 2008 22:29:33 -0800
Subject: [PATCH] --- yaml --- r: 83101 b: refs/heads/master c:
 62e1c55300f306e06478f460a7eefba085206e0b h: refs/heads/master i:   83099:
 babe53b11312e1aa8dc135bcbdb40043aada10fe v: v3

---
 [refs]              |  2 +-
 trunk/mm/migrate.c  | 30 ++++++++++++++++++++++++------
 trunk/mm/truncate.c |  2 +-
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 0c4fefe7d2c1..b881a261ee0d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7786fa9ac5366214fb942a9e62c6e46b4272c22c
+refs/heads/master: 62e1c55300f306e06478f460a7eefba085206e0b
diff --git a/trunk/mm/migrate.c b/trunk/mm/migrate.c
index 4ee4ccacf986..857a987e3690 100644
--- a/trunk/mm/migrate.c
+++ b/trunk/mm/migrate.c
@@ -640,15 +640,33 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private,
 		rcu_read_lock();
 		rcu_locked = 1;
 	}
+
 	/*
-	 * This is a corner case handling.
-	 * When a new swap-cache is read into, it is linked to LRU
-	 * and treated as swapcache but has no rmap yet.
-	 * Calling try_to_unmap() against a page->mapping==NULL page is
-	 * BUG. So handle it here.
+	 * Corner case handling:
+	 * 1. When a new swap-cache page is read into, it is added to the LRU
+	 * and treated as swapcache but it has no rmap yet.
+	 * Calling try_to_unmap() against a page->mapping==NULL page will
+	 * trigger a BUG.  So handle it here.
+	 * 2. An orphaned page (see truncate_complete_page) might have
+	 * fs-private metadata. The page can be picked up due to memory
+	 * offlining.  Everywhere else except page reclaim, the page is
+	 * invisible to the vm, so the page can not be migrated.  So try to
+	 * free the metadata, so the page can be freed.
 	 */
-	if (!page->mapping)
+	if (!page->mapping) {
+		if (!PageAnon(page) && PagePrivate(page)) {
+			/*
+			 * Go direct to try_to_free_buffers() here because
+			 * a) that's what try_to_release_page() would do anyway
+			 * b) we may be under rcu_read_lock() here, so we can't
+			 *    use GFP_KERNEL which is what try_to_release_page()
+			 *    needs to be effective.
+			 */
+			try_to_free_buffers(page);
+		}
 		goto rcu_unlock;
+	}
+
 	/* Establish migration ptes or remove ptes */
 	try_to_unmap(page, 1);
 
diff --git a/trunk/mm/truncate.c b/trunk/mm/truncate.c
index 9838c050e2dd..c35c49e54fb6 100644
--- a/trunk/mm/truncate.c
+++ b/trunk/mm/truncate.c
@@ -84,7 +84,7 @@ EXPORT_SYMBOL(cancel_dirty_page);
 
 /*
  * If truncate cannot remove the fs-private metadata from the page, the page
- * becomes anonymous.  It will be left on the LRU and may even be mapped into
+ * becomes orphaned.  It will be left on the LRU and may even be mapped into
  * user pagetables if we're racing with filemap_fault().
  *
  * We need to bale out if page->mapping is no longer equal to the original