Hi Alex, > -----Original Message----- > From: Jiri Pirko <jiri@xxxxxxxxxxx> > Sent: Friday, August 23, 2019 1:42 PM > To: Parav Pandit <parav@xxxxxxxxxxxx> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>; Jiri Pirko > <jiri@xxxxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; Kirti > Wankhede <kwankhede@xxxxxxxxxx>; Cornelia Huck <cohuck@xxxxxxxxxx>; > kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjia <cjia@xxxxxxxxxx>; > netdev@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core > > Thu, Aug 22, 2019 at 03:33:30PM CEST, parav@xxxxxxxxxxxx wrote: > > > > > >> -----Original Message----- > >> From: Jiri Pirko <jiri@xxxxxxxxxxx> > >> Sent: Thursday, August 22, 2019 5:50 PM > >> To: Parav Pandit <parav@xxxxxxxxxxxx> > >> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>; Jiri Pirko > >> <jiri@xxxxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; Kirti > >> Wankhede <kwankhede@xxxxxxxxxx>; Cornelia Huck > <cohuck@xxxxxxxxxx>; > >> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjia > >> <cjia@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx > >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core > >> > >> Thu, Aug 22, 2019 at 12:04:02PM CEST, parav@xxxxxxxxxxxx wrote: > >> > > >> > > >> >> -----Original Message----- > >> >> From: Jiri Pirko <jiri@xxxxxxxxxxx> > >> >> Sent: Thursday, August 22, 2019 3:28 PM > >> >> To: Parav Pandit <parav@xxxxxxxxxxxx> > >> >> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>; Jiri Pirko > >> >> <jiri@xxxxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; Kirti > >> >> Wankhede <kwankhede@xxxxxxxxxx>; Cornelia Huck > >> <cohuck@xxxxxxxxxx>; > >> >> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjia > >> >> <cjia@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx > >> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core > >> >> > >> >> Thu, Aug 22, 2019 at 11:42:13AM CEST, parav@xxxxxxxxxxxx wrote: > >> >> > > >> >> > > >> >> >> -----Original Message----- > >> >> >> From: Jiri Pirko <jiri@xxxxxxxxxxx> > >> >> >> Sent: Thursday, August 22, 2019 2:59 PM > >> >> >> To: Parav Pandit <parav@xxxxxxxxxxxx> > >> >> >> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>; Jiri Pirko > >> >> >> <jiri@xxxxxxxxxxxx>; David S . Miller <davem@xxxxxxxxxxxxx>; > >> >> >> Kirti Wankhede <kwankhede@xxxxxxxxxx>; Cornelia Huck > >> >> <cohuck@xxxxxxxxxx>; > >> >> >> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjia > >> >> >> <cjia@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx > >> >> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev core > >> >> >> > >> >> >> Wed, Aug 21, 2019 at 08:23:17AM CEST, parav@xxxxxxxxxxxx wrote: > >> >> >> > > >> >> >> > > >> >> >> >> -----Original Message----- > >> >> >> >> From: Alex Williamson <alex.williamson@xxxxxxxxxx> > >> >> >> >> Sent: Wednesday, August 21, 2019 10:56 AM > >> >> >> >> To: Parav Pandit <parav@xxxxxxxxxxxx> > >> >> >> >> Cc: Jiri Pirko <jiri@xxxxxxxxxxxx>; David S . Miller > >> >> >> >> <davem@xxxxxxxxxxxxx>; Kirti Wankhede > >> >> >> >> <kwankhede@xxxxxxxxxx>; Cornelia Huck <cohuck@xxxxxxxxxx>; > >> >> >> >> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; cjia > >> >> >> >> <cjia@xxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx > >> >> >> >> Subject: Re: [PATCH v2 0/2] Simplify mtty driver and mdev > >> >> >> >> core > >> >> >> >> > >> >> >> >> > > > > Just an example of the alias, not proposing how it's set. > >> >> >> >> > > > > In fact, proposing that the user does not set it, > >> >> >> >> > > > > mdev-core provides one > >> >> >> >> > > automatically. > >> >> >> >> > > > > > >> >> >> >> > > > > > > Since there seems to be some prefix overhead, as > >> >> >> >> > > > > > > I ask about above in how many characters we > >> >> >> >> > > > > > > actually have to work with in IFNAMESZ, maybe we > >> >> >> >> > > > > > > start with > >> >> >> >> > > > > > > 8 characters (matching your "index" namespace) > >> >> >> >> > > > > > > and expand as necessary for > >> >> >> disambiguation. > >> >> >> >> > > > > > > If we can eliminate overhead in IFNAMESZ, let's > >> >> >> >> > > > > > > start with > >> 12. > >> >> >> >> > > > > > > Thanks, > >> >> >> >> > > > > > > > >> >> >> >> > > > > > If user is going to choose the alias, why does it > >> >> >> >> > > > > > have to be limited to > >> >> >> >> sha1? > >> >> >> >> > > > > > Or you just told it as an example? > >> >> >> >> > > > > > > >> >> >> >> > > > > > It can be an alpha-numeric string. > >> >> >> >> > > > > > >> >> >> >> > > > > No, I'm proposing a different solution where > >> >> >> >> > > > > mdev-core creates an alias based on an abbreviated > >> >> >> >> > > > > sha1. The user does not provide the > >> >> >> >> alias. > >> >> >> >> > > > > > >> >> >> >> > > > > > Instead of mdev imposing number of characters on > >> >> >> >> > > > > > the alias, it should be best > >> >> >> >> > > > > left to the user. > >> >> >> >> > > > > > Because in future if netdev improves on the naming > >> >> >> >> > > > > > scheme, mdev will be > >> >> >> >> > > > > limiting it, which is not right. > >> >> >> >> > > > > > So not restricting alias size seems right to me. > >> >> >> >> > > > > > User configuring mdev for networking devices in a > >> >> >> >> > > > > > given kernel knows what > >> >> >> >> > > > > user is doing. > >> >> >> >> > > > > > So user can choose alias name size as it finds suitable. > >> >> >> >> > > > > > >> >> >> >> > > > > That's not what I'm proposing, please read again. > >> >> >> >> > > > > Thanks, > >> >> >> >> > > > > >> >> >> >> > > > I understood your point. But mdev doesn't know how > >> >> >> >> > > > user is going to use > >> >> >> >> > > udev/systemd to name the netdev. > >> >> >> >> > > > So even if mdev chose to pick 12 characters, it could > >> >> >> >> > > > result in > >> >> collision. > >> >> >> >> > > > Hence the proposal to provide the alias by the user, > >> >> >> >> > > > as user know the best > >> >> >> >> > > policy for its use case in the environment its using. > >> >> >> >> > > > So 12 character sha1 method will still work by user. > >> >> >> >> > > > >> >> >> >> > > Haven't you already provided examples where certain > >> >> >> >> > > drivers or subsystems have unique netdev prefixes? If > >> >> >> >> > > mdev provides a unique alias within the subsystem, > >> >> >> >> > > couldn't we simply define a netdev prefix for the mdev > >> >> >> >> > > subsystem and avoid all other collisions? I'm not in > >> >> >> >> > > favor of the user providing both a uuid and an > >> >> >> >> > > alias/instance. Thanks, > >> >> >> >> > > > >> >> >> >> > For a given prefix, say ens2f0, can two UUID->sha1 first 9 > >> >> >> >> > characters have > >> >> >> >> collision? > >> >> >> >> > >> >> >> >> I think it would be a mistake to waste so many chars on a > >> >> >> >> prefix, but > >> >> >> >> 9 characters of sha1 likely wouldn't have a collision before > >> >> >> >> we have 10s of thousands of devices. Thanks, > >> >> >> >> > >> >> >> >> Alex > >> >> >> > > >> >> >> >Jiri, Dave, > >> >> >> >Are you ok with it for devlink/netdev part? > >> >> >> >Mdev core will create an alias from a UUID. > >> >> >> > > >> >> >> >This will be supplied during devlink port attr set such as, > >> >> >> > > >> >> >> >devlink_port_attrs_mdev_set(struct devlink_port *port, const > >> >> >> >char *mdev_alias); > >> >> >> > > >> >> >> >This alias is used to generate representor netdev's phys_port_name. > >> >> >> >This alias from the mdev device's sysfs will be used by the > >> >> >> >udev/systemd to > >> >> >> generate predicable netdev's name. > >> >> >> >Example: enm<mdev_alias_first_12_chars> > >> >> >> > >> >> >> What happens in unlikely case of 2 UUIDs collide? > >> >> >> > >> >> >Since users sees two devices with same phys_port_name, user > >> >> >should destroy > >> >> recently created mdev and recreate mdev with different UUID? > >> >> > >> >> Driver should make sure phys port name wont collide, > >> >So when mdev creation is initiated, mdev core calculates the alias > >> >and if there > >> is any other mdev with same alias exist, it returns -EEXIST error > >> before progressing further. > >> >This way user will get to know upfront in event of collision before > >> >the mdev > >> device gets created. > >> >How about that? > >> > >> Sounds fine to me. Now the question is how many chars do we want to have. > >> > >12 characters from Alex's suggestion similar to git? > > Ok. > Can you please confirm this scheme looks good now? I like to get patches started. > > > >> > > >> > > >> >> in this case that it does > >> >> not provide 2 same attrs for 2 different ports. > >> >> Hmm, so the order of creation matters. That is not good. > >> >> > >> >> >> > >> >> >> >I took Ethernet mdev as an example. > >> >> >> >New prefix 'm' stands for mediated device. > >> >> >> >Remaining 12 characters are first 12 chars of the mdev alias. > >> >> >> > >> >> >> Does this resolve the identification of devlink port representor? > >> >> >Not sure if I understood your question correctly, attemping to > >> >> >answer > >> below. > >> >> >phys_port_name of devlink port is defined by the first 12 > >> >> >characters of mdev > >> >> alias. > >> >> >> I assume you want to use the same 12(or so) chars, don't you? > >> >> >Mdev's netdev will also use the same mdev alias from the sysfs to > >> >> >rename > >> >> netdev name from ethX to enm<mdev_alias>, where en=Etherenet, > >> m=mdev. > >> >> > > >> >> >So yes, same 12 characters are use for mdev's netdev and mdev > >> >> >devlink port's > >> >> phys_port_name. > >> >> > > >> >> >Is that what are you asking? > >> >> > >> >> Yes. Then you have 3 chars to handle the rest of the name (pci, pf)...
