1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 91a87f53be3c..97b601bec326 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1592,7 +1592,12 @@ static void btrfs_merge_extent_hook(struct inode *inode,
                 return;
 
         old_size = other->end - other->start + 1;
-        new_size = old_size + (new->end - new->start + 1);
+        if (old_size < (new->end - new->start + 1))
+                old_size = (new->end - new->start + 1);
+        if (new->start > other->start)
+                new_size = new->end - other->start + 1;
+        else
+                new_size = other->end - new->start + 1;
 
         /* we're not bigger than the max, unreserve the space and go */
         if (new_size <= BTRFS_MAX_EXTENT_SIZE) {