From bce4eae9864e6b6ebde5d7f05576ff0a6c3724d0 Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Thu, 24 Apr 2008 14:42:46 -0400
Subject: [PATCH] Btrfs: Fix balance_level to free the middle block if there is
 room in the left one

balance level starts by trying to empty the middle block, and then
pushes from the right to the middle.  This might empty the right block
and leave a small number of pointers in the middle.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
 fs/btrfs/ctree.c       | 35 ++++++++++++++++++++++++++++-------
 fs/btrfs/extent-tree.c |  4 ++--
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 319f9f9..29e5674 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -789,7 +789,7 @@ static int balance_level(struct btrfs_trans_handle *trans,
 	/* first, try to make some room in the middle buffer */
 	if (left) {
 		orig_slot += btrfs_header_nritems(left);
-		wret = push_node_left(trans, root, left, mid, 0);
+		wret = push_node_left(trans, root, left, mid, 1);
 		if (wret < 0)
 			ret = wret;
 		if (btrfs_header_nritems(mid) < 2)
@@ -844,6 +844,11 @@ static int balance_level(struct btrfs_trans_handle *trans,
 			ret = wret;
 			goto enospc;
 		}
+		if (wret == 1) {
+			wret = push_node_left(trans, root, left, mid, 1);
+			if (wret < 0)
+				ret = wret;
+		}
 		BUG_ON(wret == 1);
 	}
 	if (btrfs_header_nritems(mid) == 0) {
@@ -1252,17 +1257,27 @@ static int push_node_left(struct btrfs_trans_handle *trans,
 	WARN_ON(btrfs_header_generation(src) != trans->transid);
 	WARN_ON(btrfs_header_generation(dst) != trans->transid);
 
-	if (!empty && src_nritems <= 2)
+	if (!empty && src_nritems <= 8)
 		return 1;
 
 	if (push_items <= 0) {
 		return 1;
 	}
 
-	if (empty)
+	if (empty) {
 		push_items = min(src_nritems, push_items);
-	else
-		push_items = min(src_nritems - 2, push_items);
+		if (push_items < src_nritems) {
+			/* leave at least 8 pointers in the node if
+			 * we aren't going to empty it
+			 */
+			if (src_nritems - push_items < 8) {
+				if (push_items <= 8)
+					return 1;
+				push_items -= 8;
+			}
+		}
+	} else
+		push_items = min(src_nritems - 8, push_items);
 
 	copy_extent_buffer(dst, src,
 			   btrfs_node_key_ptr_offset(dst_nritems),
@@ -1308,13 +1323,19 @@ static int balance_node_right(struct btrfs_trans_handle *trans,
 	src_nritems = btrfs_header_nritems(src);
 	dst_nritems = btrfs_header_nritems(dst);
 	push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
-	if (push_items <= 0)
+	if (push_items <= 0) {
 		return 1;
+	}
+
+	if (src_nritems < 4) {
+		return 1;
+	}
 
 	max_push = src_nritems / 2 + 1;
 	/* don't try to empty the node */
-	if (max_push >= src_nritems)
+	if (max_push >= src_nritems) {
 		return 1;
+	}
 
 	if (max_push < push_items)
 		push_items = max_push;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index cc0d7f3..c49592c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -306,13 +306,13 @@ struct btrfs_block_group_cache *btrfs_find_block_group(struct btrfs_root *root,
 	int bit;
 	int ret;
 	int full_search = 0;
-	int factor = 8;
+	int factor = 10;
 
 	block_group_cache = &info->block_group_cache;
 	total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
 
 	if (!owner)
-		factor = 8;
+		factor = 10;
 
 	bit = block_group_state_bits(data);
 
-- 
2.7.4