[PATCH rfc 0/3] add support to discovery async event notifications

[hare@suse.de (Hannes Reinecke)]

On 10/16/18 3:11 AM, Sagi Grimberg wrote:
> 
>>> Oh, I don't doubt that it'll work in the sense that 'nvme 
>>> connect-all' is executed.
>>> I _do_ doubt that the 'disown' is doing anything at all; both '&' and 
>>> 'disown' will be used as arguments to '/usr/sbin/nvme', and _not_ 
>>> interpreted by any shell (as no shell is invoked in the first place).
>>> Internally udev will call 'execve' to call the new program, which 
>>> will invoke a shell only for shell scripts; binary programs will be 
>>> executed directly with not shell whatsoever.
>>
>> I see, we can run it with /bin/sh and it should do the trick?
> 
> Hannes,
> 
> Do you agree that it would suffice? Or, Do you think we should take
> a different approach?
> 
> Would like to get some feedback from others given that this is not
> a trivial decision about which way we go here..

Actually, I have looked at the original solution from James Smart for 
FC-NVMe autoconnect.

Essentially he starts a system service from a udev rule, which in itself 
is triggered by the event.
With that we're out of the udev program timeout (as systemd services can 
run for arbitrarily long) _and_ we also have resolved the problem of a 
uevent storm, as systemd will manage that for us.

The only problem here is that we need to pass arguments to the systemd 
service, but if we can use the standard udev trick of placing the 
arguments into the program environment and having the program looking 
for that we should be able to solve that, too.

Would you be okay with this approach?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
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