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Mon, 9 Feb 2026 15:23:45 +0100 (CET) Date: Mon, 9 Feb 2026 15:23:40 +0100 From: Boris Brezillon To: Thomas Zimmermann Cc: 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: <20260209152340.16f9b30a@fedora> In-Reply-To: <20260209133241.238813-6-tzimmermann@suse.de> References: <20260209133241.238813-1-tzimmermann@suse.de> <20260209133241.238813-6-tzimmermann@suse.de> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 671B180006 X-Stat-Signature: 5rynydnqemx1w7xntmm6chia49ddxey3 X-Rspam-User: X-HE-Tag: 1770647028-544400 X-HE-Meta: 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 auuacGlJ ZbojbqFKkzRy/ek7EbocoQ+F66xKP/JqONcmEA7Z9Ny8aWTbIfz2H/+00p0WfchnAd+2O/DUhWYTd+tOLIzNgUXl15VDE1w24qfM4EWRokcV71nlcR88kHov6vCKV0Wshfpuwg62/sfyjUeRrvkN4XPqBlz3BtvZ4bAEMGty+MK1yUdoz5m9HYK5AqETH4c8z/wtaHdvUcEoql4xw+JoIOaYH/+sNxyS30yMH0MfdPoVTZ8rfqQGVae79UT81kdUm/cQCGm074IW/T2ptsKOIGVuLbwHWOJRIDAv/8ACvn4XV8hP5FieAl+gsZOS0kkwMMYo/Zn3BjhacKI5iHCxpR+tfUtmZ/bKa+RuJAzklGjzpA/k9yrP4gVTQYgji4UaYOhg0mCqssAt+ztVK2EzGM3ZjTw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 9 Feb 2026 14:27:14 +0100 Thomas Zimmermann wrote: > Invoke folio_mark_accessed() in mmap page faults to add the folio to > the memory manager's LRU list. Userspace invokes mmap to get the memory > for software rendering. Compositors do the same when creating the final > on-screen image, so keeping the pages in LRU makes sense. Avoids paging > out graphics buffers when under memory pressure. > > In pfn_mkwrite, further invoke the folio_mark_dirty() to add the folio > for writeback should the underlying file be paged out from system memory. > This rarely happens in practice, yet it would corrupt the buffer content. > > This has little effect on a system's hardware-accelerated rendering, which > only mmaps for an initial setup of textures, meshes, shaders, etc. > > v3: > - rewrite for VM_PFNMAP > v2: > - adapt to changes in drm_gem_shmem_try_mmap_pmd() > > Signed-off-by: Thomas Zimmermann > Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index c3a054899ba3..0c86ad40a049 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -598,6 +598,9 @@ static vm_fault_t drm_gem_shmem_fault(struct vm_fault *vmf) > if (ret != VM_FAULT_NOPAGE) > ret = vmf_insert_pfn(vma, vmf->address, pfn); > > + if (likely(!(ret & VM_FAULT_ERROR))) Can't we just go if (ret == VM_FAULT_NOPAGE) here? > + folio_mark_accessed(folio); > + > out: > dma_resv_unlock(obj->resv); > > @@ -638,10 +641,27 @@ static void drm_gem_shmem_vm_close(struct vm_area_struct *vma) > drm_gem_vm_close(vma); > } > > +static vm_fault_t drm_gem_shmem_pfn_mkwrite(struct vm_fault *vmf) > +{ > + struct vm_area_struct *vma = vmf->vma; > + struct drm_gem_object *obj = vma->vm_private_data; > + struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); > + pgoff_t page_offset = vmf->pgoff - vma->vm_pgoff; /* page offset within VMA */ > + struct page *page = shmem->pages[page_offset]; Should we have a if (WARN_ON(!shmem->pages || page_offset <= (obj->size >> PAGE_SHIFT))) return VM_FAULT_SIGBUS; ? > + struct folio *folio = page_folio(page); > + > + file_update_time(vma->vm_file); > + > + folio_mark_dirty(folio); > + > + return 0; > +} > + > const struct vm_operations_struct drm_gem_shmem_vm_ops = { > .fault = drm_gem_shmem_fault, > .open = drm_gem_shmem_vm_open, > .close = drm_gem_shmem_vm_close, > + .pfn_mkwrite = drm_gem_shmem_pfn_mkwrite, > }; > EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops); >