Re: [PATCH v3 5/6] drm/gem-shmem: Track folio accessed/dirty status in mmap

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 28 May 2026 09:20:16 +0200
Thomas Zimmermann <tzimmermann@suse.de> wrote:

> Hi
> 
> Am 27.05.26 um 12:18 schrieb Boris Brezillon:
> [...]
> >> -			return ret;
> >> +			return vmf_insert_pfn_pmd(vmf, pfn,
> >> +						  vmf->flags & FAULT_FLAG_WRITE);  
> > I believe we can go back to
> >
> > 			return vmf_insert_pfn_pmd(vmf, pfn, false);
> >
> > if the mappings are no longer adjusted to catch write accesses.  
> 
> If we don't install it as writable now, won't the kernel not split it up 
> into 4KiB pages when the actual write happens?

It will be installed as writeable right away, regardless of the write
parameter, because if pfn_mkwrite is not implemented, vma->vm_page_prot
won't be lowered to read-only in the first place, or at least that's
what I remember from the previous debugging session I've done.