Re: [PATCH v5 1/2] btrfs: always uses root memcgroup for filemap_add_folio()

[Michal Hocko <mhocko@suse.com>]

On Fri 19-07-24 14:19:05, Qu Wenruo wrote:
[...]
> @@ -2981,8 +2982,17 @@ static int attach_eb_folio_to_filemap(struct extent_buffer *eb, int i,
>  	ASSERT(eb->folios[i]);
>  
>  retry:
> +	/*
> +	 * Btree inode is a btrfs internal inode, and not exposed to any
> +	 * user.
> +	 * Furthermore we do not want any cgroup limits on this inode.
> +	 * So we always use root_mem_cgroup as our active memcg when attaching
> +	 * the folios.
> +	 */
> +	old_memcg = set_active_memcg(root_mem_cgroup);
>  	ret = filemap_add_folio(mapping, eb->folios[i], index + i,
>  				GFP_NOFS | __GFP_NOFAIL);
> +	set_active_memcg(old_memcg);

I do not think this will compile with CONFIG_MEMCG=n

>  	if (!ret)
>  		goto finish;
>  
> -- 
> 2.45.2

-- 
Michal Hocko
SUSE Labs