From: Dan Williams dan.j.williams@intel.com
[ Upstream commit 6d24b170a9db0456f577b1ab01226a2254c016a8 ]
A CONFIG_DEBUG_KOBJECT_RELEASE test of removing a device-dax region provider (like modprobe -r dax_hmem) yields:
kobject: 'mapping0' (ffff93eb460e8800): kobject_release, parent 0000000000000000 (delayed 2000) [..] DEBUG_LOCKS_WARN_ON(1) WARNING: CPU: 23 PID: 282 at kernel/locking/lockdep.c:232 __lock_acquire+0x9fc/0x2260 [..] RIP: 0010:__lock_acquire+0x9fc/0x2260 [..] Call Trace: <TASK> [..] lock_acquire+0xd4/0x2c0 ? ida_free+0x62/0x130 _raw_spin_lock_irqsave+0x47/0x70 ? ida_free+0x62/0x130 ida_free+0x62/0x130 dax_mapping_release+0x1f/0x30 device_release+0x36/0x90 kobject_delayed_cleanup+0x46/0x150
Due to attempting ida_free() on an ida object that has already been freed. Devices typically only hold a reference on their parent while registered. If a child needs a parent object to complete its release it needs to hold a reference that it drops from its release callback. Arrange for a dax_mapping to pin its parent dev_dax instance until dax_mapping_release().
Fixes: 0b07ce872a9e ("device-dax: introduce 'mapping' devices") Signed-off-by: Dan Williams dan.j.williams@intel.com Link: https://lore.kernel.org/r/168577283412.1672036.16111545266174261446.stgit@dw... Reviewed-by: Dave Jiang dave.jiang@intel.com Reviewed-by: Fan Ni fan.ni@samsung.com Reviewed-by: Ira Weiny ira.weiny@intel.com Signed-off-by: Vishal Verma vishal.l.verma@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/dax/bus.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index c64e7076537cb..d7a838f651813 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -621,10 +621,12 @@ EXPORT_SYMBOL_GPL(alloc_dax_region); static void dax_mapping_release(struct device *dev) { struct dax_mapping *mapping = to_dax_mapping(dev); - struct dev_dax *dev_dax = to_dev_dax(dev->parent); + struct device *parent = dev->parent; + struct dev_dax *dev_dax = to_dev_dax(parent);
ida_free(&dev_dax->ida, mapping->id); kfree(mapping); + put_device(parent); }
static void unregister_dax_mapping(void *data) @@ -764,6 +766,7 @@ static int devm_register_dax_mapping(struct dev_dax *dev_dax, int range_id) dev = &mapping->dev; device_initialize(dev); dev->parent = &dev_dax->dev; + get_device(dev->parent); dev->type = &dax_mapping_type; dev_set_name(dev, "mapping%d", mapping->id); rc = device_add(dev);