Commit 56f0e661 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm/page_alloc: explicitly acquire the zone lock in __free_pages_ok 

__free_pages_ok() disables IRQs before calling a common helper
free_one_page() that acquires the zone lock.  This is not safe according
to Documentation/locking/locktypes.rst and in this context, IRQ disabling
is not protecting a per_cpu_pages structure either or a local_lock would
be used.

This patch explicitly acquires the lock with spin_lock_irqsave instead of
relying on a helper.  This removes the last instance of local_irq_save()
in page_alloc.c.

Link: https://lkml.kernel.org/r/20210512095458.30632-8-mgorman@techsingularity.net


Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 43c95bcc

mm/page_alloc.c

+8 −8
Original line number Diff line number Diff line
@@ -1590,21 +1590,21 @@ static void __free_pages_ok(struct page *page, unsigned int order, 
	unsigned long flags;

	int migratetype;

	unsigned long pfn = page_to_pfn(page);

	struct zone *zone = page_zone(page);



	if (!free_pages_prepare(page, order, true, fpi_flags))

		return;



	migratetype = get_pfnblock_migratetype(page, pfn);



	/*

	 * TODO FIX: Disable IRQs before acquiring IRQ-safe zone->lock

	 * and protect vmstat updates.

	 */

	local_irq_save(flags);

	spin_lock_irqsave(&zone->lock, flags);

	__count_vm_events(PGFREE, 1 << order);

	free_one_page(page_zone(page), page, pfn, order, migratetype,

		      fpi_flags);

	local_irq_restore(flags);

	if (unlikely(has_isolate_pageblock(zone) ||

		is_migrate_isolate(migratetype))) {

		migratetype = get_pfnblock_migratetype(page, pfn);

	}

	__free_one_page(page, pfn, zone, order, migratetype, fpi_flags);

	spin_unlock_irqrestore(&zone->lock, flags);

}



void __free_pages_core(struct page *page, unsigned int order)