From 7d0d2e8e6b6f7da221a25238cf490a095c8c4788 Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@redhat.com>
Date: Fri, 18 Mar 2011 15:13:42 -0400
Subject: Btrfs: check free space in block group before searching for a cluster

The free space cluster stuff is heavy duty, so there is no sense in going
through the entire song and dance if there isn't enough space in the block group
to begin with.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 0282033..f631df8 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1999,6 +1999,16 @@ int btrfs_find_space_cluster(struct btrfs_trans_handle *trans,
 		min_bytes = max(bytes, (bytes + empty_size) >> 2);
 
 	spin_lock(&block_group->tree_lock);
+
+	/*
+	 * If we know we don't have enough space to make a cluster don't even
+	 * bother doing all the work to try and find one.
+	 */
+	if (block_group->free_space < min_bytes) {
+		spin_unlock(&block_group->tree_lock);
+		return -ENOSPC;
+	}
+
 	spin_lock(&cluster->lock);
 
 	/* someone already found a cluster, hooray */
-- 
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