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SubjectRe: [PATCH -mm 4/10][RFC] aio: convert aio_complete to file_endio_t
On 1/15/07, David Brownell <david-b@pacbell.net> wrote:
> On Monday 15 January 2007 5:54 pm, Nate Diller wrote:
> > --- a/drivers/usb/gadget/inode.c 2007-01-12 14:42:29.000000000 -0800
> > +++ b/drivers/usb/gadget/inode.c 2007-01-12 14:25:34.000000000 -0800
> > @@ -559,35 +559,32 @@ static int ep_aio_cancel(struct kiocb *i
> > return value;
> > }
> >
> > -static ssize_t ep_aio_read_retry(struct kiocb *iocb)
> > +static int ep_aio_read_retry(struct kiocb *iocb)
> > {
> > struct kiocb_priv *priv = iocb->private;
> > - ssize_t len, total;
> > - int i;
> > + ssize_t total;
> > + int i, err = 0;
> >
> > /* we "retry" to get the right mm context for this: */
> >
> > /* copy stuff into user buffers */
> > total = priv->actual;
> > - len = 0;
> > for (i=0; i < priv->nr_segs; i++) {
> > ssize_t this = min((ssize_t)(priv->iv[i].iov_len), total);
> >
> > if (copy_to_user(priv->iv[i].iov_base, priv->buf, this)) {
> > - if (len == 0)
> > - len = -EFAULT;
> > + err = -EFAULT;
>
> Discarding the capability to report partial success, e.g. that the first N
> bytes were properly transferred? I don't see any virtue in that change.
> Quite the opposite in fact.
>
> I think you're also expecting that if N bytes were requested, that's always
> how many will be received. That's not true for packetized I/O such as USB
> isochronous transfers ... where it's quite legit (and in some cases routine)
> for the other end to send packets that are shorter than the maximum allowed.
> Sending a zero length packet is not the same as sending no packet at all,
> for another example.

I will convert this (usb) code to use the standard completion path,
which you will notice *gained* the ability to properly report both an
error and a partial success as part of this patch. In fact, fixing
this up was my intention when I wrote this patch, and the later patch
was a compromise intended to get this whole bundle out for review in a
timely manner :)

NATE
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