Btrfs: Fine tune the btree writeback exclusion some more

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8a74f90..de05525 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -214,6 +214,10 @@
 		u64 num_dirty;
 		u64 start = 0;
 		unsigned long thresh = 96 * 1024 * 1024;
+
+		if (wbc->for_kupdate)
+			return 0;
+
 		num_dirty = count_range_bits(tree, &start, thresh, EXTENT_DIRTY);
 		if (num_dirty < thresh) {
 			return 0;
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 9dd2c5c..ba624ae 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -767,7 +767,8 @@
 		num_written += write_bytes;
 
 		balance_dirty_pages_ratelimited_nr(inode->i_mapping, num_pages);
-		btrfs_btree_balance_dirty(root, 1);
+		if (num_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
+			btrfs_btree_balance_dirty(root, 1);
 		cond_resched();
 	}
 	mutex_unlock(&inode->i_mutex);