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SubjectRe: [PATCH] generic_file_sendpage
On Fri, 15 July 2005 04:06:11 -0700, Andrew Morton wrote:
> > +
> > + /* There is no sane reason to use O_DIRECT */
> > + BUG_ON(file->f_flags & O_DIRECT);
>
> err, this seems like an easy way for people to make the kernel go BUG.

Is there a sane use for O_DIRECT in combination with sendfile()?

If not, I'd like to change sys_sendfile() and return -EINVAL for
O_DIRECT file descriptors.

> > + if (unlikely(signal_pending(current)))
> > + return -EINTR;
>
> This doesn't help. The reason we've avoided file-to-file sendfile() is
> that it can cause applications to get uninterruptibly stuck in the kernel
> for ages. This code doesn't solve that problem. It needs to handle
> signal_pending() inside the main loop.
>
> And it probably needs to return a sane value (number of bytes copied)
> rather than -EINTR.

Makes sense.

> I don't know if we want to add this feature, really. It's such a
> specialised thing.

With union mount and cowlink, there are two users already. cp(1)
could use it as well, even if the improvement is quite minimal.

Jörn

--
All art is but imitation of nature.
-- Lucius Annaeus Seneca
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