[patch 5/6] mm/vmalloc: Add missing READ/WRITE_ONCE() annotations

From: Thomas Gleixner <tglx@linutronix.de>
To: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>,
	Uladzislau Rezki <urezki@gmail.com>,
	Lorenzo Stoakes <lstoakes@gmail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Baoquan He <bhe@redhat.com>
Subject: [patch 5/6] mm/vmalloc: Add missing READ/WRITE_ONCE() annotations
Date: Tue, 23 May 2023 16:02:15 +0200 (CEST)	[thread overview]
Message-ID: <20230523140002.799808756@linutronix.de> (raw)
In-Reply-To: 20230523135902.517032811@linutronix.de

purge_fragmented_blocks() accesses vmap_block::free and vmap_block::dirty
lockless for a quick check.

Add the missing READ/WRITE_ONCE() annotations.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 mm/vmalloc.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2093,9 +2093,9 @@ static bool purge_fragmented_block(struc
 		return false;
 
 	 /* prevent further allocs after releasing lock */
-	vb->free = 0;
+	WRITE_ONCE(vb->free, 0);
 	 /* prevent purging it again */
-	vb->dirty = VMAP_BBMAP_BITS;
+	WRITE_ONCE(vb->dirty, VMAP_BBMAP_BITS);
 	vb->dirty_min = 0;
 	vb->dirty_max = VMAP_BBMAP_BITS;
 	spin_lock(&vbq->lock);
@@ -2123,7 +2123,10 @@ static void purge_fragmented_blocks(int
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(vb, &vbq->free, free_list) {
-		if (!(vb->free + vb->dirty == VMAP_BBMAP_BITS && vb->dirty != VMAP_BBMAP_BITS))
+		unsigned long free = READ_ONCE(vb->free);
+		unsigned long dirty = READ_ONCE(vb->dirty);
+
+		if (!(free + dirty == VMAP_BBMAP_BITS && dirty != VMAP_BBMAP_BITS))
 			continue;
 
 		spin_lock(&vb->lock);
@@ -2231,7 +2234,7 @@ static void vb_free(unsigned long addr,
 	vb->dirty_min = min(vb->dirty_min, offset);
 	vb->dirty_max = max(vb->dirty_max, offset + (1UL << order));
 
-	vb->dirty += 1UL << order;
+	WRITE_ONCE(vb->dirty, vb->dirty + (1UL << order));
 	if (vb->dirty == VMAP_BBMAP_BITS) {
 		BUG_ON(vb->free);
 		spin_unlock(&vb->lock);


