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    SubjectRe: [PATCH 1/4] Vectorize aio_read/aio_write methods
    Badari Pulavarty <pbadari@us.ibm.com> wrote:
    >
    > static ssize_t ep_aio_read_retry(struct kiocb *iocb)
    > {
    > struct kiocb_priv *priv = iocb->private;
    > - ssize_t status = priv->actual;
    > + ssize_t len, total;
    >
    > /* we "retry" to get the right mm context for this: */
    > - status = copy_to_user(priv->ubuf, priv->buf, priv->actual);
    > - if (unlikely(0 != status))
    > - status = -EFAULT;
    > - else
    > - status = priv->actual;
    > +
    > + /* copy stuff into user buffers */
    > + total = priv->actual;
    > + len = 0;
    > + for (i=0; i < priv->count; i++) {
    > + ssize_t this = min(priv->iv[i].iov_len, total);
    > +
    > + if (copy_to_user(priv->iv[i].iov_buf, priv->buf, this))
    > + break;
    > +
    > + total -= this;
    > + len += this;
    > + if (total <= 0)
    > + break;
    > + }
    > +
    > + if (unlikely(len == 0))
    > + len = -EFAULT;

    This is still wrong, isn't it? Or am I looking at the same patch?

    There's no way in which `total' can go negative, so it'd be nicer to just
    test it for equality with zero. Because if it goes unexpectedly negative,
    we _want_ the kernel to malfunction, rather than mysteriously covering
    things up.

    The final test there should be

    if (unlikely(total != 0))

    yes?
    -
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