Messages in this thread |  | | | Date | Tue, 21 Nov 2006 11:40:21 +0100 | | From | Sébastien Dugué <> | | Subject | Re: [PATCH -mm 3/4][AIO] - AIO completion signal notification |
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Zach Brown <zach.brown@oracle.com> wrote:
> Sébastien Dugué wrote: > > AIO completion signal notification > > This is looking a lot better, thanks for keeping at it. > > > +static long aio_setup_sigevent(struct aio_notify *notify, > > + struct sigevent __user *user_event) > > +{ > > + sigevent_t event; > > + struct task_struct *target; > > + > > + if (copy_from_user(&event, user_event, sizeof (event))) > > + return -EFAULT; > > Last time we talked about this needing to call get_compat_sigevent(). I > think it still needs to.
Yes, I could not find an elegant way to tackle this, so I left it float for a while.
> > I think we should avoid the examples set by the current > compat_sys_io_submit() and get_compat_sigevent() callers. They copy > translated data on to the userspace stack and pass it to the syscalls. > That will get crazy for compat_sys_io_submit() because it would have to > rewrite the iocb and the pointer to the iocb to get sys_io_submit() to > find a copied sigevent on the stack.
Right, that's what I really wanted to avoid at all costs.
> > I think the model is compat_do_readv_writev(). Hoist some of the > syscall logic up into the compat layer so that one copying and > translating pass is made instead of trying to fool the syscall logic > into thinking that it's being called from a native word size caller.
Yes, but you end up duplicating a lot of code, but if it's the price to pay, I'm all for it.
> > So io_submit_one() should be given the kernel copies of the userspace > structures it needs. sys_io_submit() will pass it the copies it made > for native word size callers. compat_sys_io_submit() will pass in the > copies it made after translating from 32bit arguments. io_submit_one() > and lookup_kioctx() will have to be made available to kernel/compat.c > (via linux/aio.h, surely.). aio_setup_sigevent() will be called from > *_io_submit() and given the kernel sigevent, not a userspace pointer. > > Reworking things this way should have the added benefit of making 32/64 > sys_io_submit() more efficient than it is today.
I completely aggree. I will look into this.
Thanks,
Sébastien. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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