Btrfs: check for duplicate entries in the free space cache

If there are duplicate entries in the free space cache, discard the entire cache
and load it the old fashioned way.  Thanks,

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

fs/btrfs/free-space-cache.c

@@ -420,7 +420,14 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
 				spin_lock(&block_group->tree_lock);
 				ret = link_free_space(block_group, e);
 				spin_unlock(&block_group->tree_lock);
-				BUG_ON(ret);
+				if (ret) {
+					printk(KERN_ERR "Duplicate entries in "
+					       "free space cache, dumping\n");
+					kunmap(page);
+					unlock_page(page);
+					page_cache_release(page);
+					goto free_cache;
+				}
 			} else {
 				e->bitmap = kzalloc(PAGE_CACHE_SIZE, GFP_NOFS);
 				if (!e->bitmap) {
@@ -437,6 +444,14 @@ int load_free_space_cache(struct btrfs_fs_info *fs_info,
 				recalculate_thresholds(block_group);
 				spin_unlock(&block_group->tree_lock);
 				list_add_tail(&e->list, &bitmaps);
+				if (ret) {
+					printk(KERN_ERR "Duplicate entries in "
+					       "free space cache, dumping\n");
+					kunmap(page);
+					unlock_page(page);
+					page_cache_release(page);
+					goto free_cache;
+				}
 			}
 
 			num_entries--;
@@ -909,10 +924,16 @@ static int tree_insert_offset(struct rb_root *root, u64 offset,
 			 * logically.
 			 */
 			if (bitmap) {
-				WARN_ON(info->bitmap);
+				if (info->bitmap) {
+					WARN_ON_ONCE(1);
+					return -EEXIST;
+				}
 				p = &(*p)->rb_right;
 			} else {
-				WARN_ON(!info->bitmap);
+				if (!info->bitmap) {
+					WARN_ON_ONCE(1);
+					return -EEXIST;
+				}
 				p = &(*p)->rb_left;
 			}
 		}