BACKPORT: mm: page_alloc: optimize free_unref_folios()

Move direct freeing of isolated pages to the lock-breaking block in the
second loop.  This saves an unnecessary migratetype reassessment.

Minor comment and local variable scoping cleanups.

Link: https://lkml.kernel.org/r/20240320180429.678181-3-hannes@cmpxchg.org


Change-Id: I9a9dedfa7f0a0a9f18e8da11b5b6b6940fbf0fb2
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 9cbe97ba)
Bug: 420700629
[ Remove duplicated code for freeing migratetype_isolate;
  Drop !pcp_allowes_order() block, order is always 0 - Kalesh Singh ]
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>