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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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