Re: [PATCH 00/23] arch: allow pte_offset_map[_lock]() to fail

Matthew Wilcox
2023-05-10T06:07:41Z

On Tue, May 09, 2023 at 09:39:13PM -0700, Hugh Dickins wrote:
> Two: pte_offset_map() will need to do an rcu_read_lock(), with the
> corresponding rcu_read_unlock() in pte_unmap(). But most architectures
> never supported CONFIG_HIGHPTE, so some don't always call pte_unmap()
> after pte_offset_map(), or have used userspace pte_offset_map() where
> pte_offset_kernel() is more correct. No problem in the current tree,
> but a problem once an rcu_read_unlock() will be needed to keep balance.

Hi Hugh,

I shall have to spend some time looking at these patches, but at LSFMM
just a few hours ago, I proposed and nobody objected to removing
CONFIG_HIGHPTE. I don't intend to take action on that consensus
immediately, so I can certainly wait until your patches are applied, but
if this information simplifies what you're doing, feel free to act on it.