Re: [PATCH md 1 of 2] Add interface to md driver for userspace monitoring of events.

On Monday September 6, hch@lst.de wrote:

On Mon, Sep 06, 2004 at 11:05:54AM +1000, Neil Brown wrote:

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Christoph points out that this is fairly wild procfs abuse.  We want to be
moving away from that sort of thing, not adding to it.

I guess it depends on what you mean by "wild procfs abuse"...
Given that /proc/mdstat already exists it doesn't seem too
unreasonable to add a little functionality to it.  How much does it hurt?

poll on procfs is defintily abuse, even in categories of the use procfs
every times.

Oh well..  If you gain more from the patch not going in than I gain
from it going in, so be it.  I'll leave it up to Andrew/Linus.

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Is it possible to use rml's new event stuff from rc1-mm3's
kernel-sysfs-events-layer.patch?  Or a bare netlink interface?  Or
raidfs?

sysfs:  
  Probably.  I would like to improve sysfs support for md but I
  haven't taken the plunge yet to figure out how it all works.
  kevents may well be ok, but as you may need to handle
  multipath-failed events in times if high memory pressure, and need
  to handle it before pressure can be relieved, I prefer to minimise
  the number of kmallocs needed to get the event to userspace.

bare netlink:
  Probably perter sysfs... Funny, but I remember reading a comment in
  the code (2.4 I think, ages ago) about netlink being deprecated or
  something like that, so I never bothered looking at it.  I wonder
  what it meant.

netlink isn't deprecated, netlink_dev (aka netlink as chardevice nodes)
is.

Aha.. that makes sense.  Thanks for clarifying that for me.

NeilBrown