Re: Btrfs: fix up read_tree_block to return proper error

[Liu Bo <bo.li.liu@oracle.com>]

Hi Dan,

On Fri, Mar 18, 2016 at 08:37:13AM +0300, Dan Carpenter wrote:
> Hello Liu Bo,
> 
> The patch 64c043de466d: "Btrfs: fix up read_tree_block to return
> proper error" from May 25, 2015, leads to the following static
> checker warning:
> 
> 	fs/btrfs/relocation.c:1858 replace_path()
> 	error: 'eb' dereferencing possible ERR_PTR()
> 
> fs/btrfs/relocation.c
>   1850                          eb = read_tree_block(dest, old_bytenr, old_ptr_gen);
>   1851                          if (IS_ERR(eb)) {
>                                     ^^^^^^^^^^
> 
>   1852                                  ret = PTR_ERR(eb);
> 
> Missing break or continue?
> 
>   1853                          } else if (!extent_buffer_uptodate(eb)) {
>   1854                                  ret = -EIO;
>   1855                                  free_extent_buffer(eb);
>   1856                                  break;
>   1857                          }
>   1858                          btrfs_tree_lock(eb);
>                                                 ^^
> Dereference.
> 
>   1859                          if (cow) {
>   1860                                  ret = btrfs_cow_block(trans, dest, eb, parent,
>   1861                                                        slot, &eb);

Ah, thanks a lot for reporting this!

I've double checked other places in that patch, the above one is the only place
we have such a problem.

I'll cook a patch to fix it.

Thanks,

-liubo