Re: [RFC PATCH v3] mm: retry page faults under per-VMA lock when mmap_lock is not required

[Matthew Wilcox]

On Tue, Jul 07, 2026 at 05:52:31PM +0100, Lorenzo Stoakes wrote:
> +cc Vlata, the only one from the MEMORY MAPPING - LOCKING people excluded,
> and Willy as he's been heavily involved. But see below you need to cc- way
> more.

Ugh, I hadn't seen this.

No.

I've been looking into this problem, and as usual it has turned into a
yak-shaving exercise.  I think I'm five yaks deep at this point:

 - Need to start by simplifying filemap_fault
   https://lore.kernel.org/linux-mm/20260625195040.2508362-1-willy@xxxxxxxxxxxxx/
 - To do that, need to improve how we handle unlocking for faults
   (not posted because ...)
 - To do that, need to redo the hugetlb fault handler
   (not posted because ...)
 - To do that, need to get Jane's series landed
   https://lore.kernel.org/linux-mm/20260617172534.1740152-1-jane.chu@xxxxxxxxxx/
   https://lore.kernel.org/linux-mm/20260709184740.1286561-1-willy@xxxxxxxxxxxxx/
 - To do that, need to redo how we handle hwpoison of hugetlb code
   https://lore.kernel.org/linux-mm/alEpBqExnyvBnnxi@xxxxxxxxxxxxxxxxxxxx/

So yeah, I'm not impressed by the approach taken in this patch which
adds more complexity on top of a system that's creaking at the seams
with existing complexity.