On Fri, May 31, 2013 at 01:06:45PM -0400, Josef Bacik wrote:
> Dave reported a NULL pointer deref.  This is caused because he thought he'd be
> smart and add sanity checks to the extent_io bit operations, but he didn't
> expect a tree to have a NULL mapping.  To fix this we just need to init the
> relocation's processed_blocks with the btree_inode->i_mapping.  Thanks,

That fits my suspection, hhh.

Reviewed-by: Liu Bo <bo.li....@oracle.com>

> 
> Reported-by: David Sterba <dste...@suse.cz>
> Signed-off-by: Josef Bacik <jba...@fusionio.com>
> ---
>  fs/btrfs/relocation.c |    9 +++++----
>  1 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 6dbee86..1b50c41 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -4081,7 +4081,7 @@ out:
>       return inode;
>  }
>  
> -static struct reloc_control *alloc_reloc_control(void)
> +static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info 
> *fs_info)
>  {
>       struct reloc_control *rc;
>  
> @@ -4092,7 +4092,8 @@ static struct reloc_control *alloc_reloc_control(void)
>       INIT_LIST_HEAD(&rc->reloc_roots);
>       backref_cache_init(&rc->backref_cache);
>       mapping_tree_init(&rc->reloc_root_tree);
> -     extent_io_tree_init(&rc->processed_blocks, NULL);
> +     extent_io_tree_init(&rc->processed_blocks,
> +                         fs_info->btree_inode->i_mapping);
>       return rc;
>  }
>  
> @@ -4109,7 +4110,7 @@ int btrfs_relocate_block_group(struct btrfs_root 
> *extent_root, u64 group_start)
>       int rw = 0;
>       int err = 0;
>  
> -     rc = alloc_reloc_control();
> +     rc = alloc_reloc_control(fs_info);
>       if (!rc)
>               return -ENOMEM;
>  
> @@ -4310,7 +4311,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
>       if (list_empty(&reloc_roots))
>               goto out;
>  
> -     rc = alloc_reloc_control();
> +     rc = alloc_reloc_control(root->fs_info);
>       if (!rc) {
>               err = -ENOMEM;
>               goto out;
> -- 
> 1.7.7.6
> 
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