Oh yes, this part is. If you don't ensure this, everything
breaks.
At the end of an I/O operation, say to a page cache page, that
data ought to be visible equally to a userspace vs. a kernel
space mapping to that page.
For example, this is why we use language about "cpu visibility" in the
DMA api documentation and not "kernel cpu visibility" :-) And because
PIO transfers are basically pseudo-DMA they need to make the same exact
guarentees.
If you've been living in a world where you didn't think this is
necessary, I certainly feel bad for you :-)
-- David S. Miller <davem@redhat.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/