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Thu, 19 Mar 2026 15:50:33 +0100 (CET) Date: Thu, 19 Mar 2026 15:50:28 +0100 From: Boris Brezillon To: Biju Das Cc: Thomas Zimmermann , Tommaso Merciai , "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" , "linux-mm@kvack.org" , "dri-devel@lists.freedesktop.org" Subject: Re: [PATCH v4 5/6] drm/gem-shmem: Track folio accessed/dirty status in mmap Message-ID: <20260319155028.291f3157@fedora> In-Reply-To: References: <20260227114509.165572-1-tzimmermann@suse.de> <20260227114509.165572-6-tzimmermann@suse.de> <20260313111851.4c1f89f3@fedora> <20260313125644.65131b27@fedora> <20260313131835.52c5c935@fedora> <20260313134328.3166c4d0@fedora> <20260313135521.07823792@fedora> <20260313184549.08656eed@fedora> 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: rspam10 X-Rspamd-Queue-Id: 38A28100005 X-Stat-Signature: d59kr3qhude7j8cx57i8puhdrs4pd4w9 X-Rspam-User: X-HE-Tag: 1773931837-421005 X-HE-Meta: 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 XNjluPqI 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 19 Mar 2026 14:17:31 +0000 Biju Das wrote: > Hi All, > > > -----Original Message----- > > From: Biju Das > > Sent: 14 March 2026 09:43 > > Subject: RE: [PATCH v4 5/6] drm/gem-shmem: Track folio accessed/dirty status in mmap > > > > Hi Boris Brezillon, > > > > > -----Original Message----- > > > From: dri-devel On Behalf Of > > > Boris Brezillon > > > Sent: 13 March 2026 17:46 > > > Subject: Re: [PATCH v4 5/6] drm/gem-shmem: Track folio accessed/dirty > > > status in mmap > > > > > > On Fri, 13 Mar 2026 13:55:21 +0100 > > > Boris Brezillon wrote: > > > > > > > On Fri, 13 Mar 2026 13:43:28 +0100 > > > > Boris Brezillon wrote: > > > > > > > > > On Fri, 13 Mar 2026 13:18:35 +0100 Boris Brezillon > > > > > wrote: > > > > > > > > > > > On Fri, 13 Mar 2026 12:04:25 +0000 Biju Das > > > > > > wrote: > > > > > > > > > > > > > > -----Original Message----- > > > > > > > > From: dri-devel On > > > > > > > > Behalf Of Boris Brezillon > > > > > > > > Sent: 13 March 2026 11:57 > > > > > > > > Subject: Re: [PATCH v4 5/6] drm/gem-shmem: Track folio > > > > > > > > accessed/dirty status in mmap > > > > > > > > > > > > > > > > On Fri, 13 Mar 2026 11:29:47 +0100 Thomas Zimmermann > > > > > > > > wrote: > > > > > > > > > > > > > > > > > Hi > > > > > > > > > > > > > > > > > > Am 13.03.26 um 11:18 schrieb Boris Brezillon: > > > > > > > > > [...] > > > > > > > > > >>>>> + if (drm_WARN_ON(obj->dev, !shmem->pages || page_offset >= num_pages)) > > > > > > > > > >>>>> + return VM_FAULT_SIGBUS; > > > > > > > > > >>>>> + > > > > > > > > > >>>>> + file_update_time(vma->vm_file); > > > > > > > > > >>>>> + > > > > > > > > > >>>>> + > > > > > > > > > >>>>> +folio_mark_dirty(page_folio(shmem->pages[page_offse > > > > > > > > > >>>>> +t])); > > > > > > > > > > Do we need a folio_mark_dirty_lock() here? > > > > > > > > > > > > > > > > > > There is a helper for that with some documentation. [1] > > > > > > > > > > > > > > > > This [1] seems to solve the problem for me. Still unsure > > > > > > > > about the folio_mark_dirty_lock vs folio_mark_dirty though. > > > > > > > > > > > > > > > > [1]https://yhbt.net/lore/dri-devel/20260312155027.1682606-1- > > > > > > > > pedrodemargomes@gmail.com/ > > > > > > > > > > > > > > FYI, I used folio_mark_dirty_lock() still it does not solve the issue with weston hang. > > > > > > > > > > > > The patch I pointed to has nothing to do with > > > > > > folio_mark_dirty_lock(), It's a bug caused by huge page mapping changes. > > > > > > > > > > Scratch that. I had a bunch of other changes on top, and it hangs > > > > > again now that I dropped those. > > > > > > > > Seems like it's the combination of huge pages and mkwrite that's > > > > causing issues, if I disable huge pages, it doesn't hang... > > > > > > I managed to have it working with the following diff. I still need to > > > check why the "map-RO-split+RW- on-demand" approach doesn't work > > > (races between huge_fault and pfn_mkwrite?), but I think it's okay to > > > map the real thing writable on the first attempt anyway (we're not > > > trying to do CoW here, since we're always pointing to the same page, > > > it's just the permissions that change). Note that there's still the > > > race fixed by > > > https://yhbt.net/lore/dri-devel/20260312155027.1682606-1-pedrodemargom > > > es@gmail.com/ in this diff, I just tried to keep the diffstat minimal. > > > > I confirm with this diff, weston is now coming up on RZ/V2L SMARC EVK. > > > > I am just using drm-misc-next + this diff + arm64 defconfig + Poky (Yocto Project Reference Distro) > > 5.0.11 + Mesa > > > > Cheers, > > Biju > > > > > > > > --->8--- > > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c > > > b/drivers/gpu/drm/drm_gem_shmem_helper.c > > > index 4500deef4127..4efdce5a60f0 100644 > > > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > > > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > > > @@ -561,9 +561,8 @@ static vm_fault_t drm_gem_shmem_try_insert_pfn_pmd(struct vm_fault *vmf, unsigne > > > bool aligned = (vmf->address & ~PMD_MASK) == (paddr & > > > ~PMD_MASK); > > > > > > if (aligned && pmd_none(*vmf->pmd)) { > > > - /* Read-only mapping; split upon write fault */ > > > pfn &= PMD_MASK >> PAGE_SHIFT; > > > - return vmf_insert_pfn_pmd(vmf, pfn, false); > > > + return vmf_insert_pfn_pmd(vmf, pfn, vmf->flags & > > > + FAULT_FLAG_WRITE); > > > } > > > #endif > > > > > > @@ -597,8 +596,12 @@ static vm_fault_t drm_gem_shmem_fault(struct > > > vm_fault *vmf) > > > > > > pfn = page_to_pfn(page); > > > > > > - if (folio_test_pmd_mappable(folio)) > > > + if (folio_test_pmd_mappable(folio)) { > > > ret = drm_gem_shmem_try_insert_pfn_pmd(vmf, pfn); > > > + if (ret == VM_FAULT_NOPAGE && vmf->flags & FAULT_FLAG_WRITE) > > > + folio_mark_dirty(folio); > > > + } > > > + > > > if (ret != VM_FAULT_NOPAGE) > > > ret = vmf_insert_pfn(vma, vmf->address, pfn); > > > > > Any patch available to fix the weston issue? Still the issue is present with drm-misc-next > Please let me know. Not yet. I want to land [1] first. I'll try to post an official version of the proposed fix tomorrow, though I'd really like to have some inputs from the MM maintainers before claiming this is the right fix... [1]https://yhbt.net/lore/dri-devel/20260319015224.46896-1-pedrodemargomes@gmail.com/