On Thu, Jul 25, 2019 at 12:14:33PM -0600, Logan Gunthorpe wrote: > > > On 2019-07-25 12:08 p.m., Greg Kroah-Hartman wrote: > > 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? > > NVMe-OF is configured using configfs. The target is specified by the > user writing a path to a configfs attribute. This is the way it works > today but with blkdev_get_by_path()[1]. For the passthru code, we need > to get a nvme_ctrl instead of a block_device, but the principal is the same. Why isn't a fd being passed in there instead of a random string? Seems odd, but oh well, that ship sailed a long time ago for block devices I guess. So what do you actually _do_ with that char device once you have it? greg k-h
