Re: [PATCH 1/2] btrfs: Remove invalid null checks from btrfs_cleanup_dirty_bgs

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

On Thu, Feb 08, 2018 at 06:25:17PM +0200, Nikolay Borisov wrote:
> list_first_entry is essentially a wrapper over cotnainer_of. The latter
> can never return null even if it's working on inconsistent list since it
> will either crash or return some offset in the wrong struct.
> Additionally, for the dirty_bgs list the iteration is done under
> dirty_bgs_lock which ensures consistency of the list.
> 

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

-liubo

> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
> ---
>  fs/btrfs/disk-io.c | 9 ---------
>  1 file changed, 9 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index aca906971abe..1b3989c54d7c 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -4323,11 +4323,6 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
>  		cache = list_first_entry(&cur_trans->dirty_bgs,
>  					 struct btrfs_block_group_cache,
>  					 dirty_list);
> -		if (!cache) {
> -			btrfs_err(fs_info, "orphan block group dirty_bgs list");
> -			spin_unlock(&cur_trans->dirty_bgs_lock);
> -			return;
> -		}
>  
>  		if (!list_empty(&cache->io_list)) {
>  			spin_unlock(&cur_trans->dirty_bgs_lock);
> @@ -4351,10 +4346,6 @@ void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
>  		cache = list_first_entry(&cur_trans->io_bgs,
>  					 struct btrfs_block_group_cache,
>  					 io_list);
> -		if (!cache) {
> -			btrfs_err(fs_info, "orphan block group on io_bgs list");
> -			return;
> -		}
>  
>  		list_del_init(&cache->io_list);
>  		spin_lock(&cache->lock);
> -- 
> 2.7.4
>