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Thu, 28 May 2026 11:11:46 +0200 (CEST) Date: Thu, 28 May 2026 11:11:40 +0200 From: Boris Brezillon To: Thomas Zimmermann Cc: Igor Torrente , loic.molinari@collabora.com, willy@infradead.org, frank.binns@imgtec.com, matt.coster@imgtec.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch, dri-devel@lists.freedesktop.org, linux-mm@kvack.org Subject: Re: [PATCH v3 5/6] drm/gem-shmem: Track folio accessed/dirty status in mmap Message-ID: <20260528111140.2d9535b7@fedora> In-Reply-To: <4a00d72c-9b87-4511-9da0-bcb40fae4d74@suse.de> References: <20260209133241.238813-1-tzimmermann@suse.de> <20260209133241.238813-6-tzimmermann@suse.de> <850e8355-7884-405c-a70a-986ce032c019@suse.de> <831c0943-c75f-4d42-aa5f-90ce34cf8530@collabora.com> <67855fcd-2afe-4a1d-a51a-210e45f56167@suse.de> <20260527121832.7264f0db@fedora> <4a00d72c-9b87-4511-9da0-bcb40fae4d74@suse.de> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; 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> >> + 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.