Re: [PATCH v6 04/16] nvme-core: introduce nvme_get_by_path()

[Keith Busch]

On Thu, Jul 25, 2019 at 02:28:28PM -0600, Logan Gunthorpe wrote:
> 
> 
> On 2019-07-25 1:58 p.m., Keith Busch wrote:
> > On Thu, Jul 25, 2019 at 11:54:18AM -0600, Logan Gunthorpe wrote:
> >>
> >>
> >> On 2019-07-25 11:50 a.m., Matthew Wilcox wrote:
> >>> On Thu, Jul 25, 2019 at 11:23:23AM -0600, Logan Gunthorpe wrote:
> >>>> nvme_get_by_path() is analagous to blkdev_get_by_path() except it
> >>>> gets a struct nvme_ctrl from the path to its char dev (/dev/nvme0).
> >>>>
> >>>> The purpose of this function is to support NVMe-OF target passthru.
> >>>
> >>> I can't find anywhere that you use this in this patchset.
> >>>
> >>
> >> Oh sorry, the commit message is out of date the function was actually
> >> called nvme_ctrl_get_by_path() and it's used in Patch 10.
> > 
> > Instead of by path, could we have configfs take something else, like
> > the unique controller instance or serial number? I know that's different
> > than how we handle blocks and files, but that way nvme core can lookup
> > the cooresponding controller without adding new cdev dependencies.
> 
> Well the previous version of the patchset just used the ctrl name
> ("nvme1") and looped through all the controllers to find a match. But
> this sucks because of the inconsistency and the fact that the name can
> change if hardware changes and the number changes. Allowing the user to
> make use of standard udev rules seems important to me.

Should we then create a new udev rule for persistent controller
names? /dev/nvme1 may not be the same controller each time you refer
to it.