mm/page_alloc: avoid overcounting bulk alloc in watermark check

mm/page_alloc: avoid overcounting bulk alloc in watermark check

alloc_pages_bulk_noprof() only fills NULL slots and already tracks how
many entries are pre-populated via nr_populated.

The fast watermark check was adding nr_pages unconditionally, which can
overestimate the demand.  Use (nr_pages - nr_populated) instead, as an
upper bound on the remaining pages this call can still allocate without
scanning the whole array.

Link: https://lkml.kernel.org/r/tencent_F36C5B5FB4DED98C79D9BDEE1210CD338C06@qq.com
Signed-off-by: Shengming Hu <hu.shengming@zte.com.cn>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>