Re: [PATCH net-next 3/4] bpf: add support for persistent maps/progs

From: Alexei Starovoitov
Date: Fri Oct 16 2015 - 13:32:10 EST


On 10/16/15 9:43 AM, Hannes Frederic Sowa wrote:
Hi Alexei,

On Fri, Oct 16, 2015, at 18:18, Alexei Starovoitov wrote:
On 10/16/15 3:25 AM, Hannes Frederic Sowa wrote:
Namespaces at some point dealt with the same problem, they nowadays use
bind mounts of/proc/$$/ns/* to some place in the file hierarchy to keep
the namespace alive. This at least allows someone to build up its own
hierarchy with normal unix tools and not hidden inside a C-program. For
filedescriptors we already have/proc/$$/fd/* but it seems that doesn't
work out of the box nowadays.

bind mounting of /proc/../fd was initially proposed by Andy and we've
looked at it thoroughly, but after discussion with Eric it became
apparent that it doesn't fit here. At the end we need shell tools
to access maps.

Oh yes, I want shell tools for this very much! Maybe even that things
like strings, grep etc. work. :)

yes and the only way to get there is to have it done via fs.

Also I think you missed the hierarchy in this patch set _is_ built with
normal 'mkdir' and files are removed with 'rm'.

I did not miss that, I am just concerned that if the kernel does not
enforce such a hierarchy automatically it won't really happen.

if it's easier for user to work with single level of directories,
it should be able to do so. It's not a job of the kernel to enforce
how user space apps should be designed.

Oh, tracing does not allow daemons. Why? I can only imagine embedded
users, no?

yes and for networking: restartability and HA.
cannot really do that with fuse/daemons.

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