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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Aze8xafZ; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E338606A331; Fri, 6 Nov 2026 21:50:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Aze8xafZ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 062D11F008A1; Fri, 6 Nov 2026 21:50:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794001805; bh=Sp+/rZLBk58dvEP4ySui6/tvD/UNJbnX6ljbENoMxUA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Aze8xafZlbHSmp3d9gsGH2mJakJ8WzD3a2I45CcQLXgo64iNKE9xQZkacX0lkm+9H hRcq5aQCb7lhna/x+9R8R7cPJekBVR8qzl+vs0kvEjC7gv4hCBavI2iFcZHoyBbIxk OsKrdYgxpffMHW2RcNCeXDXQNPHXmOMTR3X8A07Lcck4kt6GhplMauazqY8/y91dGC MbIV/XErrSL3SDbgNCcMMult+cttS6IGg4xRe5v8Uks98nl//+qeG3FmmaFZdaMpcR di+qSJ9HSlfFF9zMdStZ/es33HXVWlqN+tgeWgCWrszeElUjZPfB/2tkbYIgPhsF+9 E3nvl4tKuSHPQ== Message-ID: <54d9955d-a3ac-4aac-98e3-75dec5c64294@kernel.org> Date: Fri, 6 Nov 2026 22:48:13 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: use folio_dup_file_rmap_pud() in copy_huge_pud() To: Konstantin Khorenko , Zi Yan , Andrew Morton , Lorenzo Stoakes , Alistair Popple , Dan Williams Cc: linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org References: <20261106-khorenko-vstor-151183-copy_huge_pud-dup-rmap-v1-1-cf8ee4fafabb@virtuozzo.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/6/26 18:05, Konstantin Khorenko wrote: > copy_huge_pud() adds the child's rmap of a device DAX PUD with > folio_add_file_rmap_pud(). That helper maps a folio afresh: it updates > NR_FILE_MAPPED when the folio becomes mapped and mlocks it in a > VM_LOCKED VMA. Neither applies at fork: the parent keeps the folio mapped > under the page table lock, and dup_mmap() clears VM_LOCKED in the > child's VMA. > > copy_present_ptes() duplicates the rmap of a PTE with > folio_dup_file_rmap_ptes(), which only raises the mapcounts. Add > folio_dup_file_rmap_pud() for the PUD level and use it in copy_huge_pud(). > > No functional change. > > Reviewed-by: David Hildenbrand (Arm) > Reviewed-by: Zi Yan > Signed-off-by: Konstantin Khorenko > --- > David's fix for the device DAX PUD fork bug, commit d90bdc02e36e > ("mm/huge_memory: properly handle refcounted PUD mappings on fork"), > went in before v2 of my series for the same bug [1]. > > This is the follow-up David asked for [2]. > > The Reviewed-by tags are from v2 patch 1, whose rmap.h hunk and > copy_huge_pud() line this patch carries unchanged. > > The selftest from v2 [3] is not included, as it needs a real devdax > device. It is there for anyone who wants to run it. > > Based on thp-7.5.misc of the mm/core tree. > > [1] https://lore.kernel.org/all/20261105-vstor-150143-copy_huge_pud-folio-refcount-v2-0-2828fe5a51ed@virtuozzo.com/ > [2] https://lore.kernel.org/all/6f035f97-8b55-47ad-bd52-833b86b8ae8f@kernel.org/ > [3] https://lore.kernel.org/all/20261105-vstor-150143-copy_huge_pud-folio-refcount-v2-2-2828fe5a51ed@virtuozzo.com/ > > Assisted-by: LLM > --- Reviewed-by: David Hildenbrand (Arm) Thanks, I'll wait a bit and then pick this up. -- Cheers, David