On 25.08.21 11:40, Dan Carpenter wrote:
Hello David Hildenbrand,
The patch 6cc26d77613a: "virtio-mem: use page_offline_(start|end)
when setting PageOffline()" from Jun 30, 2021, leads to the following
Smatch static checker warning:
drivers/virtio/virtio_mem.c:1072 virtio_mem_set_fake_offline()
warn: sleeping in atomic context
drivers/virtio/virtio_mem.c
1069 static void virtio_mem_set_fake_offline(unsigned long pfn,
1070 unsigned long nr_pages, bool onlined)
1071 {
--> 1072 page_offline_begin();
virtio_mem_online_page_cb() is holding rcu_read_lock() so calling
page_offline_begin() here is sleeping in atomic bug.
1073 for (; nr_pages--; pfn++) {
1074 struct page *page = pfn_to_page(pfn);
1075
1076 __SetPageOffline(page);
1077 if (!onlined) {
1078 SetPageDirty(page);
1079 /* FIXME: remove after cleanups */
1080 ClearPageReserved(page);
1081 }
1082 }
1083 page_offline_end();
1084 }
Ah, thanks for that report!
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 09ed55de07d7..9e9922c60da4 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -1242,12 +1242,19 @@ static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
do_online = virtio_mem_bbm_get_bb_state(vm, id) !=
VIRTIO_MEM_BBM_BB_FAKE_OFFLINE;
}
+
+ /*
+ * virtio_mem_set_fake_offline() might sleep, we don't need
+ * the device anymore. See virtio_mem_remove() how races
+ * with device removal are avoided.
+ */
+ rcu_read_unlock();
+
if (do_online)
generic_online_page(page, order);
else
virtio_mem_set_fake_offline(PFN_DOWN(addr), 1 << order,
false);
- rcu_read_unlock();
return;
}
rcu_read_unlock();
Will send out a patch shortly.
--
Thanks,
David / dhildenb
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