Re: [RFC PATCH 00/57] mm/collapse: rebuild collapse on migration primitives

[David Hildenbrand (Arm)]

On 9/15/26 12:46, Kiryl Shutsemau wrote:
> On Mon, Sep 14, 2026 at 05:07:37PM +0200, David Hildenbrand (Arm) wrote:
>>> As I mentioned above, we drop the ptl after the freeze. And take it a
>>> second time for the install.  Allocation and the copy run in between with
>>> no lock held -- on 64K the copy at PMD order is 512M of it, which is why
>>> it cannot sit under either lock.
>>
>> Hold on, are freezing all folios to collapse? That cannot possibly work with
>> COW-shared folios that are mapped into other address spaces.
> 
> I break COW for worthy candidates in the faultin prepass before freeze,
> alongside swapin. It simplifies the picture substantially. No rmap mess.

Hm, okay. So temporary memory allocations and page copying.

-- 
Cheers,

David