fujita.tomonori@xxxxxxxxxxxxx wrote on Wed, 09 Jan 2008 09:11 +0900:
> On Tue, 8 Jan 2008 17:09:18 -0500
> Pete Wyckoff <pw@xxxxxxx> wrote:
> > I took another look at the compat approach, to see if it is feasible
> > to keep the compat handling somewhere else, without the use of #ifdef
> > CONFIG_COMPAT and size-comparison code inside bsg.c. I don't see how.
> > The use of iovec is within a write operation on a char device. It's
> > not amenable to a compat_sys_ or a .compat_ioctl approach.
> >
> > I'm partial to #1 because the use of architecture-independent fields
> > matches the rest of struct sg_io_v4. But if you don't want to have
> > another iovec type in the kernel, could we do #2 but just return
> > -EINVAL if the need for compat is detected? I.e. change
> > dout_iovec_count to dout_iovec_length and do the math?
>
> If you are ok with removing the write/read interface and just have
> ioctl, we could can handle comapt stuff like others do. But I think
> that you (OSD people) really want to keep the write/read
> interface. Sorry, I think that there is no workaround to support iovec
> in bsg.
I don't care about read/write in particular. But we do need some
way to launch asynchronous SCSI commands, and currently read/write
are the only way to do that in bsg. The reason is to keep multiple
spindles busy at the same time.
How about these new ioctls instead of read/write:
SG_IO_SUBMIT - start a new blk_execute_rq_nowait()
SG_IO_TEST - complete and return a previous req
SG_IO_WAIT - wait for a req to finish, interruptibly
Then old write users will instead do ioctl SUBMIT. Read users will
do TEST for non-blocking fd, or WAIT for blocking. And SG_IO could
be implemented as SUBMIT + WAIT.
Then we can do compat_ioctl and convert up iovecs out-of-line before
calling the normal functions.
Let me know if you want a patch for this.
-- Pete
-
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
