mm/page_alloc: correct return value when failing at preparing

mainline inclusion
from mainline-5.14-rc2
commit e5c15cea
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I3ZVL2
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e5c15cea339115edf99dc92282865f173cf84510

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

If the array passed in is already partially populated, we should return
"nr_populated" even failing at preparing arguments stage.

Link: https://lkml.kernel.org/r/20210713152100.10381-3-mgorman@techsingularity.net


Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Link: https://lore.kernel.org/r/20210709102855.55058-1-yanfei.xu@windriver.com


Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit e5c15cea)
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>
Reviewed-by: tong tiangen <tongtiangen@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>