Hi Matthew,
On 2024/2/5 02:54, Matthew Wilcox wrote:
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.
The reason I first noticed this is that we didn't allocate and
initialize the ptlock in __pte_alloc_one_kernel(). So in at the PTE
level, the implementation of kernel & user page tables is already
different.
Thanks.
