Re: [PATCH 0/2] nvmet: add namespace-level debugfs for reservation state

[Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Jul 06, 2026 / 18:28, Guixin Liu wrote:
> 
> 
> 在 2026/7/6 15:59, Daniel Wagner 写道:
> > On Mon, Jul 06, 2026 at 11:10:41AM +0800, Guixin Liu wrote:
> > > > > > Example output with two registered hosts and an active holder:
> > > > > > 
> > > > > >     $ cat /sys/kernel/debug/nvmet/testnqn/ns1/reservation
> > > > > >     enable : 1
> > > > > >     generation : 2
> > > > > >     notify_mask : 0x0
> > > > > >     rtype : write_exclusive
> > > > > >     holder : hostid=11111111-1111-1111-1111-111111111111, rkey=0x1111
> > > > > >     registrants:
> > > > > >       hostid=11111111-1111-1111-1111-111111111111, rkey=0x1111
> > > > > >       hostid=22222222-2222-2222-2222-222222222222, rkey=0x2222
> > > > > I expect blktests will make use of this interface eventually. The parser
> > > > > for this wont be dead simple, sure doable but not simple. If you see a
> > > > > way to make a bit simpler I wouldn't mind.
> > > > How about this:
> > > > 
> > > > 1. One holer, multi registrants:
> > > >    enable=1
> > > >    generation=2
> > > >    notify_mask=0x0
> > > >    rtype=write_exclusive
> > > >    holder=11111111-1111-1111-1111-111111111111,0x1111
> > > >    reg=11111111-1111-1111-1111-111111111111,0x1111
> > > >    reg=22222222-2222-2222-2222-222222222222,0x2222
> > > > 
> > > > 2. No holder, multi registrants:
> > > >    enable=1
> > > >    generation=1
> > > >    notify_mask=0x0
> > > >    rtype=none
> > > >    holder=none
> > > >    reg=11111111-1111-1111-1111-111111111111,0x1111
> > > >    reg=22222222-2222-2222-2222-222222222222,0x2222
> > > > 
> > > > 3. No registrant:
> > > >    enable=1
> > > >    generation=0
> > > >    notify_mask=0x0
> > > >    rtype=none
> > > >    holder=none
> > > > 
> > > > 4. Reservation not enabled:
> > > >    enable=0
...
> Hi Shin'ichiro:
>     Does this work for you?

Hi Guixin, yes, I think it is good enough. If this is sysfs, "one value
per file" and "array by files in a directory" would be guided, but this is
debugfs readonly data. So, it sounds reasonable to put some data structure into
a single debufs attribute file. Uevent like key=value format sounds good. It is
a bit wacky to use comma to hold both host id and key for a holder and a
registrant, but I cannot think of better solution.