diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c3fa12a6b59e604d6324d85fef68c9173e26a656..1897f3a65b4fd5846c0bd55212bc1a5069e48eea 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -899,5 +899,5 @@ int btrfs_alloc_file_extent(struct btrfs_trans_handle *trans,
 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid,
-			     u64 blocknr, u64 num_blocks, int mod);
+			     u64 blocknr, int mod);
 #endif
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 09de270c5a521ec5d8b7fbc4e880a77584653430..5230a44cb19b9eed44ec5e9a82d248454c9e1630 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -26,6 +26,7 @@ int btrfs_alloc_file_extent(struct btrfs_trans_handle *trans,
 
 	ret = btrfs_insert_empty_item(trans, root, &path, &file_key,
 				      sizeof(*item));
+	BUG_ON(ret);
 	item = btrfs_item_ptr(btrfs_buffer_leaf(path.nodes[0]), path.slots[0],
 			      struct btrfs_file_extent_item);
 	btrfs_set_file_extent_disk_blocknr(item, ins.objectid);
@@ -42,7 +43,7 @@ int btrfs_alloc_file_extent(struct btrfs_trans_handle *trans,
 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid,
-			     u64 blocknr, u64 num_blocks, int mod)
+			     u64 offset, int mod)
 {
 	int ret;
 	struct btrfs_key file_key;
@@ -50,7 +51,7 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 	int cow = mod != 0;
 
 	file_key.objectid = objectid;
-	file_key.offset = blocknr;
+	file_key.offset = offset;
 	file_key.flags = 0;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 	ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index fd3d9d616ff9a65d34d71e1a12d89d25d98020b4..f2f08189903d33c16d7121da1b737cf7580a3398 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -697,7 +697,8 @@ static int btrfs_get_block(struct inode *inode, sector_t iblock,
 
 
 	ret = btrfs_lookup_file_extent(trans, root, &path,
-				       inode->i_ino, iblock, 1, 0);
+				       inode->i_ino,
+				       iblock << inode->i_blkbits, 0);
 	if (ret < 0) {
 		btrfs_release_path(root, &path);
 		err = ret;
@@ -737,6 +738,7 @@ static int btrfs_get_block(struct inode *inode, sector_t iblock,
 	}
 
 	extent_start = btrfs_disk_key_offset(&leaf->items[path.slots[0]].key);
+	extent_start = extent_start >> inode->i_blkbits;
 	extent_start += btrfs_file_extent_offset(item);
 	extent_end = extent_start + btrfs_file_extent_num_blocks(item);
 	btrfs_release_path(root, &path);
@@ -751,7 +753,8 @@ static int btrfs_get_block(struct inode *inode, sector_t iblock,
 		err = 0;
 		goto out;
 	}
-	ret = btrfs_alloc_file_extent(trans, root, objectid, iblock,
+	ret = btrfs_alloc_file_extent(trans, root, objectid,
+				      iblock << inode->i_blkbits,
 				      1, extent_end, &blocknr);
 	if (ret) {
 		err = ret;