Re: [Qemu-devel] [PATCH 2/2] i_generation / st_gen support for handle based fs driver

[Stefan Hajnoczi]

On Thu, Aug 4, 2011 at 1:03 PM, Aneesh Kumar K.V
<address@hidden> wrote:
> On Thu, 4 Aug 2011 12:47:42 +0100, Stefan Hajnoczi <address@hidden> wrote:
>> On Thu, Aug 4, 2011 at 12:20 PM, Aneesh Kumar K.V
>> <address@hidden> wrote:
>> > On Thu, 4 Aug 2011 11:21:05 +0100, Stefan Hajnoczi <address@hidden> wrote:
>> >> On Thu, Aug 4, 2011 at 11:06 AM, Harsh Prateek Bora
>> >> <address@hidden> wrote:
>> >> > This patch provides support for st_gen for handle based fs type server.
>> >> > Currently the support is provided for ext4, btrfs, reiserfs and xfs.
>> >> >
>> >> > Signed-off-by: Harsh Prateek Bora <address@hidden>
>> >> > ---
>> >> >  hw/9pfs/virtio-9p-handle.c |   30 ++++++++++++++++++++++++++++++
>> >> >  1 files changed, 30 insertions(+), 0 deletions(-)
>> >>
>> >> Does handle-based file I/O really need to duplicate all this code?  Is
>> >> it possible to use either regular open or handle-based open from a
>> >> single local fs codebase?
>> >
>> > The only details common between handle based and local based getversion
>> > callback is the ioctl. Moving that into a helper may not really help in
>> > this case ?.
>>
>> Aneesh, do you have a public virtfs tree that I can look at?  In
>> qemu.git we don't have virtio-9p-handle.c yet, so I can't give any
>> specific feedback.
>
> http://repo.or.cz/w/qemu/v9fs.git for-upstream
>
> I should send the patchset to qemu list soon. Was waiting for the
> co-routine patches to go upstream.

The handle code looks like a copy of the local backend minus security
models.  It just needs to use handle syscalls instead of using paths.

If you treat the path as the "handle" and use regular openat(2), then
the handle code could do what the local backend does today.  Except
compared to the local backend it would not have security models and be
a bit slower due to extra syscalls.

Is the plan to add security models to the handle backend?  If so, then
handle and local will be equivalent and duplicate code.

Stefan