Two fixes based on Vlastimil's review of the defrag_mode patches.

#1 fixes a bug that can lead to memory deadlocks on high-CPU-count
machines. This affects not just defrag_mode.

#2 fixes an overreclaim issue when defrag_mode is enabled.

Based on:

  commit 16176182efbf3dfce6dad18dcc8801164329d1c2 (akpm/mm-hotfixes-unstable)
  Author: Uros Bizjak <ubizjak@gmail.com>
  Date:   Fri Apr 4 12:24:37 2025 +0200

 include/linux/mmzone.h |  2 --
 mm/page_alloc.c        | 12 ------------
 mm/vmscan.c            | 29 ++++++++++++++++++++++++++---
 3 files changed, 26 insertions(+), 17 deletions(-)