Messages in this thread | | | Date | Tue, 16 Jan 2007 01:21:24 -0800 | From | "Nate Diller" <> | Subject | Re: [PATCH -mm 4/10][RFC] aio: convert aio_complete to file_endio_t |
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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 :)
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