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>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 954b047639ab..78ced11d18c7 100644
--- a/fs/btrfs/extent_map.c
+++ b/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) {