mm: introduce clear_pages() and clear_user_pages()

mm: introduce clear_pages() and clear_user_pages()

Introduce clear_pages(), to be overridden by architectures that support
more efficient clearing of consecutive pages.

Also introduce clear_user_pages(), however, we will not expect this
function to be overridden anytime soon.

As we do for clear_user_page(), define clear_user_pages() only if the
architecture does not define clear_user_highpage().

That is because if the architecture does define clear_user_highpage(),
then it likely needs some flushing magic when clearing user pages or
highpages.  This means we can get away without defining
clear_user_pages(), since, much like its single page sibling, its only
potential user is the generic clear_user_highpages() which should instead
be using clear_user_highpage().

Link: https://lkml.kernel.org/r/20260107072009.1615991-3-ankur.a.arora@oracle.com
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzessutek Wilk <konrad.wilk@oracle.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Li Zhe <lizhe.67@bytedance.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>