Re: [RFC v1 1/3] mm/mmu_notifier: Add a new notifier for mapping updates (new pages)

Alistair Popple
2023-07-25T03:40:04Z

Jason Gunthorpe <jgg@nvidia.com> writes:

> On Mon, Jul 24, 2023 at 07:54:38AM +0000, Kasireddy, Vivek wrote:

>> And replace mmu_notifier_update_mapping(vma->vm_mm, address, pte_pfn(*ptep))
>> in the current patch with
>> mmu_notifier_change_pte(vma->vm_mm, address, ptep, false));
>
> It isn't very useful because nothing can do anything meaningful under
> the PTLs. Can't allocate memory for instance.

Yeah, although you already have to be pretty careful allocating memory
from a notifier while holding any lock as it may trigger direct reclaim
which can call the same notifier leading to a recursive lock.

A totally different discussion though.

> JAson