Btrfs: Fix add_extent_mapping to check for duplicates across the whole range

add_extent_mapping was allowing the insertion of overlapping extents.
This never used to happen because it only inserted the extents from disk
and those were never overlapping.

But, with the data=ordered code, the disk and memory representations of the
file are not the same.  add_extent_mapping needs to ensure a new extent
does not overlap before it inserts.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent_map.c

@@ -207,7 +207,14 @@ int add_extent_mapping(struct extent_map_tree *tree,
 	int ret = 0;
 	struct extent_map *merge = NULL;
 	struct rb_node *rb;
+	struct extent_map *exist;
 
+	exist = lookup_extent_mapping(tree, em->start, em->len);
+	if (exist) {
+		free_extent_map(exist);
+		ret = -EEXIST;
+		goto out;
+	}
 	assert_spin_locked(&tree->lock);
 	rb = tree_insert(&tree->map, em->start, &em->rb_node);
 	if (rb) {

fs/btrfs/inode.c

@@ -641,6 +641,7 @@ int btrfs_readpage_io_hook(struct page *page, u64 start, u64 end)
 		if (ret == -ENOENT || ret == -EFBIG)
 			ret = 0;
 		csum = 0;
+		if (printk_ratelimit())
 			printk("no csum found for inode %lu start %Lu\n", inode->i_ino,
 			       start);
 		goto out;
@@ -1653,8 +1654,20 @@ static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
 		btrfs_truncate_page(inode->i_mapping, inode->i_size);
 
 		hole_size = block_end - hole_start;
+		while(1) {
+			struct btrfs_ordered_extent *ordered;
 			btrfs_wait_ordered_range(inode, hole_start, hole_size);
+
 			lock_extent(io_tree, hole_start, block_end - 1, GFP_NOFS);
+			ordered = btrfs_lookup_ordered_extent(inode, hole_start);
+			if (ordered) {
+				unlock_extent(io_tree, hole_start,
+					      block_end - 1, GFP_NOFS);
+				btrfs_put_ordered_extent(ordered);
+			} else {
+				break;
+			}
+		}
 
 		trans = btrfs_start_transaction(root, 1);
 		btrfs_set_trans_block_group(trans, inode);