Re: [Xen-devel] [PATCH 0 of 9 RFC] blktap3: Introduce a small subset of blktap3 files

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-11-16 at 18:25 +0000, Thanos Makatos wrote:
> blktap3 is a disk backend driver. It is based on blktap2 but does not require
> the blktap/blkback kernel modules as it allows tapdisk to talk directly to
> blkfront. This primarily simplifies maintenance, and _may_ lead to performance
> improvements. This patch series introduces a small subset of files required by
> blktap3. blktap3 is based on a blktap2 fork maintained mostly by Citrix (it
> lives in github), so these changes are also imported, apart from the blktap3
> ones.

Sorry it took so long to look at this series, it generally looks good,
thanks. I made a couple of minor comments on some patches and I noticed
that I agreed with many of your TODOs.

Can you list explicitly what is in the patch, I think it's the central
dispatcher/ctl daemon, which spawns the tapdisk processes on demand, but
not the tapdisk process itself?

It might also be useful to give a high level overview of the
architecture. Could you enumerate what the moving parts are and how they
fit together?

For example, I think, but I'm guessing a bit, that there is a daemon
which watches xenstore and spawns processes on demand, is that right? Is
that daemon called "tap-ctl"

There is also an RPC mechanism for talking to either that daemon or the
individual tapdisk process and a library for clients to speak it? This
is unix domain socket based or something else?

Ian.


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