mm: page_alloc: use migrate_disable() in drain_local_pages_wq()

drain_local_pages_wq() disables preemption to avoid CPU migration during
CPU hotplug and can't use cpus_read_lock().

Using migrate_disable() works here, too.  The scheduler won't take the
CPU offline until the task left the migrate-disable section.  The
problem with disabled preemption here is that drain_local_pages()
acquires locks which are turned into sleeping locks on PREEMPT_RT and
can't be acquired with disabled preemption.

Use migrate_disable() in drain_local_pages_wq().

Link: https://lkml.kernel.org/r/20211015210933.viw6rjvo64qtqxn4@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6714039..2aafc33 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3141,9 +3141,9 @@ static void drain_local_pages_wq(struct work_struct *work)
         * cpu which is alright but we also have to make sure to not move to
         * a different one.
         */
-       preempt_disable();
+       migrate_disable();
        drain_local_pages(drain->zone);
-       preempt_enable();
+       migrate_enable();
 }
 
 /*