[PATCH 2/4] cxl/mem: Fix cdev_device_add() error handling

[Dan Williams]

If cdev_device_add() fails then the allocation performed by
dev_set_name() is leaked. Use put_device(), not open coded release, for
device_add() failures.

The comment is obsolete because direct err_id failures need not worry
about the device being live.

The release method expects the percpu_ref is already dead, so
percpu_ref_kill() is needed before put_device(). However, given that the
cdev was partially live wait_for_completion() also belongs in the
release method.

Fixes: b39cb1052a5c ("cxl/mem: Register CXL memX devices")
Reported-by: Jason Gunthorpe <j...@nvidia.com>
Signed-off-by: Dan Williams <dan.j.willi...@intel.com>
---
 drivers/cxl/mem.c |   16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 30bf4f0f3c17..e53d573ae4ab 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -1049,6 +1049,7 @@ static void cxl_memdev_release(struct device *dev)
 {
        struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
 
+       wait_for_completion(&cxlmd->ops_dead);
        percpu_ref_exit(&cxlmd->ops_active);
        ida_free(&cxl_memdev_ida, cxlmd->id);
        kfree(cxlmd);
@@ -1157,7 +1158,6 @@ static void cxlmdev_unregister(void *_cxlmd)
 
        percpu_ref_kill(&cxlmd->ops_active);
        cdev_device_del(&cxlmd->cdev, dev);
-       wait_for_completion(&cxlmd->ops_dead);
        cxlmd->cxlm = NULL;
        put_device(dev);
 }
@@ -1210,20 +1210,16 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
        cdev_init(cdev, &cxl_memdev_fops);
 
        rc = cdev_device_add(cdev, dev);
-       if (rc)
-               goto err_add;
+       if (rc) {
+               percpu_ref_kill(&cxlmd->ops_active);
+               put_device(dev);
+               return rc;
+       }
 
        return devm_add_action_or_reset(dev->parent, cxlmdev_unregister, cxlmd);
 
-err_add:
-       ida_free(&cxl_memdev_ida, cxlmd->id);
 err_id:
-       /*
-        * Theoretically userspace could have already entered the fops,
-        * so flush ops_active.
-        */
        percpu_ref_kill(&cxlmd->ops_active);
-       wait_for_completion(&cxlmd->ops_dead);
        percpu_ref_exit(&cxlmd->ops_active);
 err_ref:
        kfree(cxlmd);