Re: [Nbd] [PATCH] nbd: Support FUA, FLUSH and ROTATIONAL

[Paul Clements <paul.clements@...856...>]

On Tue, Aug 2, 2011 at 5:20 PM, Wouter Verhelst <w@...112...> wrote:
> On Tue, Aug 02, 2011 at 11:58:11AM -0400, Paul Clements wrote:
>> One question to the general audience: do we need an ioctl for the flag
>> setting or would a sysfs entry be sufficient? I really would like to
>> move away from having so many ioctls in nbd. I've started converting
>> some debug and ioctl stuff to sysfs already...
>
> Me, I don't really care either way.
>
> I suppose the NBD_DO_IT ioctl will need to remain, since handing an fd
> through a write in a totally unrelated file is going to be *very* ugly.

Yeah, I have to say, the passing of the socket fd through the ioctl
was a pretty clever hack by Pavel.

> Other than that, I guess moving communication between client and server
> to sysfs entries makes more sense.

And if we could eventually get rid of all ioctls other than NBD_DO_IT,
then the unusual nature of NBD_DO_IT being a long-lived ioctl would
not be a problem. Normally, ioctls are locked against each other, but
you obviously can't do that when one of the ioctls lasts for the life
of the device. :)

At any rate, check the patches when they come through and let me know
if they're providing what we need userland-wise. I think I'll take the
approach of trying to provide everything via sysfs that is now
available via ioctl, and then deprecate the ioctls (at some [probably
very] future date down the road)...

--
Paul