Re: [Qemu-devel] [PATCH 12/16] scsi-generic: use plain ioctl

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Sat, 2010-11-20 at 01:25 +0000, adq wrote:
> On 20 November 2010 00:41, Nicholas A. Bellinger <nab@linux-iscsi.org> wrote:
> > On Fri, 2010-11-19 at 19:39 +0100, Christoph Hellwig wrote:
> >> On Thu, Nov 18, 2010 at 03:47:36PM +0100, Hannes Reinecke wrote:
> >> >
> >> > aio_ioctl is emulated anyway and currently broken.
> >>
> >> What's broken about it currently?
> >
> > Mmmmmm, I do not recall this being broken in the first place..?  There
> > was a single issue with megasas+bdrv_aio_ioctl() with WinXP (that did
> > not appear with lsi53c895a) that was mentioned on the list earlier in
> > the year that required a patch to use bdev_ioctl(), but last I recall
> > Hannes had already fixed this in recent megasas.c code w/ 32-bit MSFT
> > guests.  Also, this is what I have been with scsi_generic.c and
> > scsi_bsg.c into TCM_loop in my v0.12.5 megasas tree, and I am not
> > observing any obvious issues with AIO IOCTLs for SG_IO/BSG into Linux
> > guests.
> >
> > I will give AIO IOCTL ops a run with these on v2.6.37-rc2 lock-less KVM
> > host mode <-> TCM_Loop to verify against the v0.12.5 megasas tree.
> 
> Could this AIO ioctl breakage perhaps be the one I fixed here?
> http://web.archiveorange.com/archive/v/1XS1vROmfC7dN9wYxsmt
> 
> The patch is defintely in the latest git... it works fine for me with
> my scsi-generic MMC command patches.
> 

Interesting read, and thanks for the heads up on this bit..   I do not
personally recall running into any issues with TYPE_DISK w/ lsi53c895a
and AIO SG_IO into WinXP guests on v0.12.5 code.   After a quick double
check in the v0.12.5 megasas tree, the proper get_async_context_id() is
still present:

http://git.kernel.org/?p=virt/kvm/nab/qemu-kvm.git;a=blob;f=posix-aio-compat.c;h=ccdbf9a16d0ef1d7e57c87dbe43f318d4c7a5967;hb=HEAD#l560

So it appears this acb->async_context_id was incorrectly dropped during
v0.13 development, and with your fix commited into v0.13 mainline code
that Hannes should be able to safetly drop this the megasas series,
yes..?

Thank you for your comments!

--nab