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From:   David Hildenbrand <david@redhat.com>
To:     linux-kernel@vger.kernel.org
Cc:     David Hildenbrand <david@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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Subject: [PATCH v1 6/7] virtio-mem: use page_offline_(start|end) when setting PageOffline()
Date:   Thu, 29 Apr 2021 14:25:18 +0200
Message-Id: <20210429122519.15183-7-david@redhat.com>
In-Reply-To: <20210429122519.15183-1-david@redhat.com>
References: <20210429122519.15183-1-david@redhat.com>
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Let's properly use page_offline_(start|end) to synchronize setting
PageOffline(), so we won't have valid page access to unplugged memory
regions from /proc/kcore.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 drivers/virtio/virtio_mem.c | 2 ++
 mm/util.c                   | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 10ec60d81e84..dc2a2e2b2ff8 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -1065,6 +1065,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
 static void virtio_mem_set_fake_offline(unsigned long pfn,
 					unsigned long nr_pages, bool onlined)
 {
+	page_offline_begin();
 	for (; nr_pages--; pfn++) {
 		struct page *page = pfn_to_page(pfn);
 
@@ -1075,6 +1076,7 @@ static void virtio_mem_set_fake_offline(unsigned long pfn,
 			ClearPageReserved(page);
 		}
 	}
+	page_offline_end();
 }
 
 /*
diff --git a/mm/util.c b/mm/util.c
index 95395d4e4209..d0e357bd65e6 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1046,8 +1046,10 @@ void page_offline_begin(void)
 {
 	down_write(&page_offline_rwsem);
 }
+EXPORT_SYMBOL(page_offline_begin);
 
 void page_offline_end(void)
 {
 	up_write(&page_offline_rwsem);
 }
+EXPORT_SYMBOL(page_offline_end);
-- 
2.30.2