Ming Zhang wrote:
I, personally, don't like an interface, like tgtadm, which tries to do
all non-trivial configuration work from a single command line tool,
because of the following 3 reasons:
1. It's a lot of effort to write and maintain such a tool, because it
needs to be extensible to work with new modules and modes. For instance,
iptables tool is 86K lines long. The whole netfilter code for all
network protocols in the kernel is less that 50K lines long. Do we want
such a code bloat (170% of code to configure) and dedicated team of
maintainers to solve a fundamentally simple configuration task?
2. It assumes the stateless type of configuration, when each call
configures exactly one thing without any side effects on already
configured or future entries. This approach is good for cases like
iptables, but for SCSI targets it's possible that several configuration
steps require to be done in an atomic manner, like adding an iSCSI
target and configuring its parameters.
3. It's hard to read 5+ parameters in one command line, so it's a lot
easier to make a mistake there.
So, I believe, a configuration interface should be rather /proc or /sys
interface based. I don't think we should care much about backward
compatibility with tgtadm, because the existing interface doesn't reach
the state of being widely used. As I already mentioned, only ibmvscsi at
the moment uses it, hardware for which is pretty rare.
forget about proc. configfs is better. but problem is how u configure
user space target with configfs?
It doesn't matter much for me procfs or configfs or sysfs, although I
definitely would prefer procfs, because it's already used by SCST, so no
additional effort is needed. (The choice of procfs was purely for
historical reasons; SCST was originally made for 2.4 kernels, where
there were no other alternatives). But it doesn't relate to the choice
of the fundamental approach "single utility for all possible parameters"
vs "single entry for each parameter".
Thus, I would suggest that before making the further move we should also
consider configuration interfaces of SCST and LIO and choose the best
things from all 3.
Vlad
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