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

On 9/15/26 12:46, Kiryl Shutsemau wrote:

On Mon, Sep 14, 2026 at 05:07:37PM +0200, David Hildenbrand (Arm) wrote:

quoted

quoted

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