Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path()

From: Greg Kroah-Hartman
Date: Thu Jul 25 2019 - 14:09:25 EST

On Thu, Jul 25, 2019 at 11:53:20AM -0600, Logan Gunthorpe wrote:
> On 2019-07-25 11:40 a.m., Greg Kroah-Hartman wrote:
> > On Thu, Jul 25, 2019 at 11:23:21AM -0600, Logan Gunthorpe wrote:
> >> cdev_get_by_path() attempts to retrieve a struct cdev from
> >> a path name. It is analagous to blkdev_get_by_path().
> >>
> >> This will be necessary to create a nvme_ctrl_get_by_path()to
> >> support NVMe-OF passthru.
> >
> > Ick, why? Why would a cdev have a "pathname"?
> So we can go from "/dev/nvme0" (which points to a char device) to its
> struct cdev and eventually it's struct nvme_ctrl. Doing it this way also
> allows supporting symlinks that might be created by udev rules.

Why do you have a "string" within the kernel and are not using the
normal open() call from userspace on the character device node on the
filesystem in your namespace/mount/whatever?

Where is this random string coming from? Why is this so special that no
one else has ever needed it?


greg k-h