mm, memory_hotplug: update pcp lists everytime onlining a memory block

mainline inclusion
from mainline-v5.9-rc1
commit de1193f0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8GREH
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=de1193f0be66f88e2c6d0fd965137668fc2ec4a5



--------------------------------

When onlining a first memory block in a zone, pcp lists are not updated
thus pcp struct will have the default setting of ->high = 0,->batch = 1.

This means till the second memory block in a zone(if it have) is onlined
the pcp lists of this zone will not contain any pages because pcp's
->count is always greater than ->high thus free_pcppages_bulk() is called
to free batch size(=1) pages every time system wants to add a page to the
pcp list through free_unref_page().

To put this in a word, system is not using benefits offered by the pcp
lists when there is a single onlineable memory block in a zone.  Correct
this by always updating the pcp lists when memory block is onlined.

Fixes: 1f522509 ("mem-hotplug: avoid multiple zones sharing same boot strapping boot_pageset")
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Link: http://lkml.kernel.org/r/1596372896-15336-1-git-send-email-charante@codeaurora.org


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Conflicts:
	mm/memory_hotplug.c
Signed-off-by: Liu Shixin <liushixin2@huawei.com>