Re: [PATCH] memcg: page_cgroup_ino() get memcg from compound_head(page)

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

On Mon, 13 Mar 2023 08:34:52 +0000 Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:

> From: Hugh Dickins <hughd@xxxxxxxxxx>
> 
> In a kernel with added WARN_ON_ONCE(PageTail) in page_memcg_check(), we
> observed a warning from page_cgroup_ino() when reading
> /proc/kpagecgroup.

If this is the only known situation in which page_memcg_check() is
passed a tail page, why does page_memcg_check() have

	if (PageTail(page))
		return NULL;

?  Can we remove this to simplify, streamline and clarify?