[166/192] mm/page_alloc: explicitly acquire the zone lock in __free_pages_ok

Commit Message

Andrew Morton June 29, 2021, 2:41 a.m. UTC

From: Mel Gorman <[e-mail]>
Subject: 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/[e-mail]
Signed-off-by: Mel Gorman <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Chuck Lever <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jesper Dangaard Brouer <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Sebastian Andrzej Siewior <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/page_alloc.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Patch

--- a/mm/page_alloc.c~mm-page_alloc-explicitly-acquire-the-zone-lock-in-__free_pages_ok
+++ a/mm/page_alloc.c
@@ -1590,21 +1590,21 @@  static void __free_pages_ok(struct page
 	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)