From 9f46f38b316c329f6d5e6b46fe02e84ac6a3ac53 Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Fri, 31 Jul 2009 14:57:55 -0400
Subject: [PATCH] --- yaml --- r: 156509 b: refs/heads/master c:
 013f1b12f4fc479f697acae2f31bad220162cd03 h: refs/heads/master i:   156507:
 6e4d146520df3ab81a672e9844ebaa7d7e294724 v: v3

---
 [refs]                       |  2 +-
 trunk/fs/btrfs/extent-tree.c | 21 +++++++++++++++++----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index eaf3bf39f60b..eaffc658d01a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6606bb97e146a387932efee263745b7240a11193
+refs/heads/master: 013f1b12f4fc479f697acae2f31bad220162cd03
diff --git a/trunk/fs/btrfs/extent-tree.c b/trunk/fs/btrfs/extent-tree.c
index dc84daee6bc4..72a2b9c28e9f 100644
--- a/trunk/fs/btrfs/extent-tree.c
+++ b/trunk/fs/btrfs/extent-tree.c
@@ -265,10 +265,6 @@ static int caching_kthread(void *data)
 
 	atomic_inc(&block_group->space_info->caching_threads);
 	last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
-again:
-	/* need to make sure the commit_root doesn't disappear */
-	down_read(&fs_info->extent_commit_sem);
-
 	/*
 	 * We don't want to deadlock with somebody trying to allocate a new
 	 * extent for the extent root while also trying to search the extent
@@ -282,6 +278,10 @@ static int caching_kthread(void *data)
 	key.objectid = last;
 	key.offset = 0;
 	btrfs_set_key_type(&key, BTRFS_EXTENT_ITEM_KEY);
+again:
+	/* need to make sure the commit_root doesn't disappear */
+	down_read(&fs_info->extent_commit_sem);
+
 	ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
 	if (ret < 0)
 		goto err;
@@ -304,6 +304,19 @@ static int caching_kthread(void *data)
 
 			if (need_resched() ||
 			    btrfs_transaction_in_commit(fs_info)) {
+				leaf = path->nodes[0];
+
+				/* this shouldn't happen, but if the
+				 * leaf is empty just move on.
+				 */
+				if (btrfs_header_nritems(leaf) == 0)
+					break;
+				/*
+				 * we need to copy the key out so that
+				 * we are sure the next search advances
+				 * us forward in the btree.
+				 */
+				btrfs_item_key_to_cpu(leaf, &key, 0);
 				btrfs_release_path(fs_info->extent_root, path);
 				up_read(&fs_info->extent_commit_sem);
 				schedule_timeout(1);