Btrfs: remove BUG_ON()'s in btrfs_map_block

btrfs_map_block can go horribly wrong in the face of fs corruption, lets agree
to not be assholes and panic at any possible chance things are all fucked up.

Signed-off-by: Josef Bacik <jbacik@fb.com>
[ removed type casts ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -5290,7 +5290,15 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 	stripe_nr = div64_u64(stripe_nr, stripe_len);
 
 	stripe_offset = stripe_nr * stripe_len;
-	BUG_ON(offset < stripe_offset);
+	if (offset < stripe_offset) {
+		btrfs_crit(fs_info, "stripe math has gone wrong, "
+			   "stripe_offset=%llu, offset=%llu, start=%llu, "
+			   "logical=%llu, stripe_len=%llu",
+			   stripe_offset, offset, em->start, logical,
+			   stripe_len);
+		free_extent_map(em);
+		return -EINVAL;
+	}
 
 	/* stripe_offset is the offset of this block in its stripe*/
 	stripe_offset = offset - stripe_offset;
@@ -5531,7 +5539,13 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, int rw,
 				&stripe_index);
 		mirror_num = stripe_index + 1;
 	}
-	BUG_ON(stripe_index >= map->num_stripes);
+	if (stripe_index >= map->num_stripes) {
+		btrfs_crit(fs_info, "stripe index math went horribly wrong, "
+			   "got stripe_index=%u, num_stripes=%u",
+			   stripe_index, map->num_stripes);
+		ret = -EINVAL;
+		goto out;
+	}
 
 	num_alloc_stripes = num_stripes;
 	if (dev_replace_is_ongoing) {