[PATCH v2 3/3] mm/memory_hotplug: fix unpaired mem_hotplug_begin/done

Jia He
2020-07-07T05:59:50Z

When check_memblock_offlined_cb() returns failed rc(e.g. the memblock is
online at that time), mem_hotplug_begin/done is unpaired in such case.

Therefore a warning:
Call Trace:
percpu_up_write+0x33/0x40
try_remove_memory+0x66/0x120
? _cond_resched+0x19/0x30
remove_memory+0x2b/0x40
dev_dax_kmem_remove+0x36/0x72 [kmem]
device_release_driver_internal+0xf0/0x1c0
device_release_driver+0x12/0x20
bus_remove_device+0xe1/0x150
device_del+0x17b/0x3e0
unregister_dev_dax+0x29/0x60
devm_action_release+0x15/0x20
release_nodes+0x19a/0x1e0
devres_release_all+0x3f/0x50
device_release_driver_internal+0x100/0x1c0
driver_detach+0x4c/0x8f
bus_remove_driver+0x5c/0xd0
driver_unregister+0x31/0x50
dax_pmem_exit+0x10/0xfe0 [dax_pmem]

Fixes: f1037ec0cc8a ("mm/memory_hotplug: fix remove_memory() lockdep splat")
Cc: stable@vger.kernel.org # v5.6+
Signed-off-by: Jia He <justin.he@arm.com>
---
mm/memory_hotplug.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index da374cd3d45b..76c75a599da3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1742,7 +1742,7 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)
*/
rc = walk_memory_blocks(start, size, NULL, check_memblock_offlined_cb);
if (rc)
- goto done;
+ return rc;

/* remove memmap entry */
firmware_map_remove(start, start + size, "System RAM");
@@ -1766,9 +1766,8 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size)

try_offline_node(nid);

-done:
mem_hotplug_done();
- return rc;
+ return 0;
}

/**
--
2.17.1