Btrfs: fix duplicate checking logic

When merging my code into the integration test the second check for duplicate
entries got screwed up.  This patch fixes it by dropping ret2 and just using ret
for the return value, and checking if we got an error before adding the bitmap
to the local list.  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 8258ccf8..38f3fd9 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -250,7 +250,7 @@
 	pgoff_t index = 0;
 	unsigned long first_page_offset;
 	int num_checksums;
-	int ret = 0, ret2;
+	int ret = 0;
 
 	INIT_LIST_HEAD(&bitmaps);
 
@@ -421,11 +421,10 @@
 					goto free_cache;
 				}
 				spin_lock(&ctl->tree_lock);
-				ret2 = link_free_space(ctl, e);
+				ret = link_free_space(ctl, e);
 				ctl->total_bitmaps++;
 				ctl->op->recalc_thresholds(ctl);
 				spin_unlock(&ctl->tree_lock);
-				list_add_tail(&e->list, &bitmaps);
 				if (ret) {
 					printk(KERN_ERR "Duplicate entries in "
 					       "free space cache, dumping\n");
@@ -434,6 +433,7 @@
 					page_cache_release(page);
 					goto free_cache;
 				}
+				list_add_tail(&e->list, &bitmaps);
 			}
 
 			num_entries--;