In one test, when modprobe zram, no zram device was found in the /dev. 
But don't see any errors printed in jouranls/dmesg. Later we found out 
that the reason was that device_add() did not check its return value when
calling devtmpfs_create_node(). So we hope to turn devtmpfs_*_node() & 
devtmpfs_submit_req() into a function with no return value, and add some
debug info in the handle() that actually processes the request to let the
user know why the creation was not successful.

Patch [1] devtmpfs: convert to pr_fmt. 
Patch [2] devtmpfs: add debug info to handle().
Patch [3] devtmpfs: Remove return value of devtmpfs_*_node() & 
devtmpfs_submit_req().

Longlong Xia (3):
  devtmpfs: convert to pr_fmt
  devtmpfs: add debug info to handle()
  devtmpfs: remove return value of devtmpfs_*_node() &
    devtmpfs_submit_req()

 drivers/base/base.h     |  8 +++----
 drivers/base/devtmpfs.c | 48 +++++++++++++++++++++++------------------
 2 files changed, 31 insertions(+), 25 deletions(-)

-- 
2.25.1