Re: [PATCH 2/2] mm: pgtable: remove unnecessary split ptlock for kernel PMD page

[Matthew Wilcox]

On Thu, Feb 01, 2024 at 04:05:41PM +0800, Qi Zheng wrote:
> For kernel PMD entry, we use init_mm.page_table_lock to protect it, so
> there is no need to allocate and initialize the split ptlock for kernel
> PMD page.

I don't think this is a great idea.  Maybe there's no need to initialise
it, but keeping things the same between kernel & user page tables is a
usually better.  We don't normally allocate memory for the spinlock,
it's only in debugging scenarios like LOCKDEP.  I would drop this unless
you have a really compelling argument to make.