[RFC PATCH] software node: Skip duplicated software_node sysfs

[Qian Cai <quic_qiancai@xxxxxxxxxxx>]

A recent commit allowed device_create_managed_software_node() to call
software_node_notify() which could generate duplicated "software_node"
sysfs files. For example,

"/devices/platform/808622B7:01/xhci-hcd.3.auto/software_node"

Since it was created earlier from another path,

  sysfs_create_link
  software_node_notify
  device_add
  platform_device_add
  dwc3_host_init
  dwc3_probe
  platform_probe
  really_probe.part.0
  really_probe
  __driver_probe_device
  driver_probe_device
  __driver_attach
  bus_for_each_dev
  driver_attach
  bus_add_driver
  driver_register
  __platform_driver_register
  dwc3_driver_init at drivers/usb/dwc3/core.c:2072
  do_one_initcall

Fixed it by using sysfs_create_link_nowarn() in software_node_notify() to
avoid those bad messages during booting,

sysfs: cannot create duplicate filename '/devices/platform/808622B7:01/xhci-hcd.3.auto/software_node'
 Call trace:
  dump_backtrace
  show_stack
  dump_stack_lvl
  dump_stack
  sysfs_warn_dup
  sysfs_do_create_link_sd.isra.0
  sysfs_create_link
  software_node_notify
  device_create_managed_software_node
  iort_named_component_init
  iort_iommu_configure_id
  acpi_dma_configure_id
  platform_dma_configure
  really_probe.part.0
  really_probe
  __driver_probe_device
  driver_probe_device
  __driver_attach
  bus_for_each_dev
  driver_attach
  bus_add_driver
  driver_register
  __platform_driver_register
  xhci_plat_init
  do_one_initcall
  kernel_init_freeable
  kernel_init
  ret_from_fork

Fixes: 5aeb05b27f81 ("software node: balance refcount for managed software nodes")
Signed-off-by: Qian Cai <quic_qiancai@xxxxxxxxxxx>
---
 drivers/base/swnode.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 4debcea4fb12..0a266c312aa3 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -1126,17 +1126,15 @@ void software_node_notify(struct device *dev)
 	if (!swnode)
 		return;
 
-	ret = sysfs_create_link(&dev->kobj, &swnode->kobj, "software_node");
-	if (ret)
+	ret = sysfs_create_link_nowarn(&dev->kobj, &swnode->kobj,
+				       "software_node");
+	if (ret && ret != -EEXIST)
 		return;
 
-	ret = sysfs_create_link(&swnode->kobj, &dev->kobj, dev_name(dev));
-	if (ret) {
+	if (!sysfs_create_link(&swnode->kobj, &dev->kobj, dev_name(dev)))
+		kobject_get(&swnode->kobj);
+	else if (!ret)
 		sysfs_remove_link(&dev->kobj, "software_node");
-		return;
-	}
-
-	kobject_get(&swnode->kobj);
 }
 
 void software_node_notify_remove(struct device *dev)
-- 
2.30.2