memcg: convert mem_cgroup_move_charge_pte_range() to use a folio

Patch series "Convert memcontrol charge moving to use folios".

No part of these patches should change behaviour; all the called functions
already convert from page to folio, so this ought to simply be a reduction
in the number of calls to compound_head().  


This patch (of 4):

Remove many calls to compound_head() by calling page_folio() once at the
start of each stanza which receives a struct page from 'target'.  There
should be no change in behaviour here as all the called functions start
out by converting the page to its folio.

Link: https://lkml.kernel.org/r/20240111181219.3462852-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20240111181219.3462852-2-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>