From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 70579CA5FC5 for ; Wed, 30 Sep 2026 14:08:03 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4hvxhf01gbz3017; Thu, 01 Oct 2026 00:08:02 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2607:f8b0:4864:3b::10" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1790777281; cv=none; b=OWcK0iA/x0ZvxHbwsHiRSSYEs7H8ItMKOoW8A1QWqY7Ui314jZrnGozJouu5JNG2sWjjYbXI4OIEJHJi5hFCXIyIqcX+tZXc7omSCfGOzH+MTGgZWpEIiKXtksiCpbEKNtNf++VI0iEpmnRVW0RPSa25tsymvF46xMyQq3GP8YTV07aFUxG08fKS6LXBBKGYgag0qn6Pez+4CWD7GNSoQ+bjA3aIHTeTK6NavJgye2IEW3py/2VctEkia5taSM+xk6cBjTeuB/CUKbzMlqsmoubGrehuhQJHXqVxu1FP5qalYDGSY0aKNAiqI15GP9lCyr+c6Fht5jqlCeBlyy1CLg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1790777281; c=relaxed/relaxed; bh=SfMxtfxa+3COrIjgzxsQNjSW0BqNRs0OC1S2RzR7Pys=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=L3lO+nLMzeZ9zVqc7qFGIzoKP5dWwpXmrj0JIyMiQQSpQOKh6NINP+ZEMT+AiSlX9LfvKho4ZBThoDBt0bCmd7CWj9Hq35ZBRDQr2RzPHupISJX5OqPXzCHwy2kli/RVrcIDxY8zDs6k6yByAmafomR3QmSQX5aFZ/77/HU2fP/D/Zxw8K9/HFV4qtqPjW7RxbqBZNyXwOGKeO+H2qY7jr3xW6sJBrB/YTh0FVu9a4zDmJNpplJVkIb6mxfz4grn4HM7F1W1DjVptSOhHxbHfdJckLU7FDNjrfzG7oAryeaxHVO2pdASdNRDfj+FQYHXIngmtbhtfIQOOIkaGZQOAQ== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; dkim=pass (2048-bit key; unprotected) header.d=bytedance.com header.i=@bytedance.com header.a=rsa-sha256 header.s=google header.b=U0fI9aL8; dkim-atps=neutral; spf=pass (client-ip=2607:f8b0:4864:3b::10; helo=mail-pz2-x10.google.com; envelope-from=songmuchun@bytedance.com; receiver=lists.ozlabs.org) smtp.mailfrom=bytedance.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=bytedance.com header.i=@bytedance.com header.a=rsa-sha256 header.s=google header.b=U0fI9aL8; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=bytedance.com (client-ip=2607:f8b0:4864:3b::10; helo=mail-pz2-x10.google.com; envelope-from=songmuchun@bytedance.com; receiver=lists.ozlabs.org) Received: from mail-pz2-x10.google.com (mail-pz2-x10.google.com [IPv6:2607:f8b0:4864:3b::10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4hvxhd2jwTz2y24 for ; Thu, 01 Oct 2026 00:08:01 +1000 (AEST) Received: by mail-pz2-x10.google.com with SMTP id 41be03b00d2f7-cc4c08393b0so2399286a12.0 for ; Wed, 30 Sep 2026 07:08:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1790777279; x=1791382079; darn=lists.ozlabs.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=SfMxtfxa+3COrIjgzxsQNjSW0BqNRs0OC1S2RzR7Pys=; b=U0fI9aL8uORWqAGCRKtjly2VtZMXmyymWyakH8+KIsmoS7UcKpVhqTkZ/bDf+JdIi1 Y2p9Hk2CwHrw/aMvTbn2tvLPs3KgKzKzdnE4I2swHImlVS52Bl/8/GFyYCsUVpHIniWz lZhu0b4nlziiOKc7b9Al2Gy25VeUQwmiUDkxF6UDfiHmm2n20hk/1/HteoWlMx2va29l e3/8tYgo1louSNQcUzp6kYBffADeufRB6tLiWWeomrqVTCkqEePSgzOI79WoxHO1uXRm tUPvbCDMVrJSvfGEj0tdFa2+d/nNk76Xlap1kYaObVX6xrllg4WIiHhTF2l+P4lUspBC Apog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790777279; x=1791382079; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=SfMxtfxa+3COrIjgzxsQNjSW0BqNRs0OC1S2RzR7Pys=; b=2o8q79RBUBLkYHoy5OPyPCvVcbVMHTRPG8cp6GtwH/B9iMwJP8EzlzC7EWVa/mPOun ilhE9omUiIkeXx9C0u90gIdhiL6vjC+lX/xK5uhNewbr8aSIm5Og/XE8YZsEYy1yBROi qCE07Q+mF3kH2ci28muPxVjjU9GPAcHA7iuWG10aB5qG+ZTj42qKv/M8XI83GJdP6fLQ kPHhsriQ2wPoYvE2jZeMhKBSNXHnLgCRNn5+CWizpIr4r4OqDRtF29TkYP51efxX3wor g9EjjpSDqxl7CD5/OEOT/v4wuQmodgyDJqJJnH4qddoPUumRZ5SKSzTta1hNZWbBg/5N FktA== X-Forwarded-Encrypted: i=1; AKwUvBw7ZE/fgMNnunqxUPyQKGl4XguCipJtJ3aTTWDCFTYUXl5Dauc7bnJVe0m/47c6Rhbmrc6xebGu1twjL24=@lists.ozlabs.org X-Gm-Message-State: AFq9FYIyxX9qpW1LFlyIwTcQEDezlOF/CzeJmHMgqSem4PN5teUB2h/N 5eNkBPUqLNNhJIVZ3WVD0nDmatFm6bowlC89otPDYslPsWBB5QPXrF1wBtBI5R2umnE= X-Gm-Gg: AYBFou3lU8lUEBRLis5PNrvLB6PvYHCcZHqjRUpPuwuCA5FagvZapOlahZbsbNkzJyo j7eWMC8E1apwUyOoSiL8k6HuVXLCmaCYHkPHCFeRCB9fKYkY3gSuOHip34NZYdrKCzl67t58s4D H1rEHyCWEHrdCFXOIZBlA05G481N9E078pN9aew0bUcZd0dAg8pGVdGs1wp564GHZmCD7E9E7Td 5LPpp+d8wGiu3ZmWzQXd3mPOl1/05mgQEXLBNdZEv4XYcFWaxTtnj5n+ktDSX1rlpYrS2OQZV+k gUmY00EWegF8xt2kN/2k9kgaTk9Ltom2ueDIrYsTJ6AvoVPHFqBLFAAdANDCuZuOLFqatEffBx/ FkxuLstuPYuAXxpTfUpAY5GM5/Q1afEdW7JpzL8aYifgoGRQ9rPECYdEPViewJCRU2/yrt9t2QY f4umeTuGfba8Hq22A1qAA4gawGC5IergW5bVJDKoNbl9lx6B8OIeXdZcTYQW0e9HCtCrEPWXv72 D0RRA5c/ChVqA== X-Received: by 2002:a17:90b:4acf:b0:39e:4c7f:8b1b with SMTP id 98e67ed59e1d1-3a4d19d23e4mr1306484a91.32.1790777279220; Wed, 30 Sep 2026 07:07:59 -0700 (PDT) Received: from G6L4RL2QG9 ([139.177.225.238]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a4e60ea12csm639509a91.1.2026.09.30.07.07.51 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Wed, 30 Sep 2026 07:07:58 -0700 (PDT) From: Muchun Song To: Andrew Morton , David Hildenbrand , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Muchun Song , Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Ritesh Harjani , Shrikanth Hegde , Randy Dunlap , Muchun Song , Lance Yang Subject: [PATCH v6 05/12] mm/sparse-vmemmap: prepare DAX vmemmap population for compound page orders Date: Wed, 30 Sep 2026 22:06:20 +0800 Message-ID: <20260930140627.57431-6-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260930140627.57431-1-songmuchun@bytedance.com> References: <20260930140627.57431-1-songmuchun@bytedance.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Device DAX still uses vmemmap_populate_compound_pages() to populate its compound-page vmemmap mappings. That helper allocates the head and first tail vmemmap pages explicitly, then reuses the first tail page for the remaining tail page mappings. Device DAX is being moved to the section-based vmemmap optimization infrastructure, but it cannot switch to the generic section-based population path yet. Once a later patch records the DAX compound page order in section metadata, DAX head and first-tail PFNs can look optimizable to the generic helpers as well. Rename the existing VMEMMAP_POPULATE_PAGEREF flag to VMEMMAP_POPULATE_DAX and pass it through all paths in vmemmap_populate_compound_pages() during this transition. This keeps DAX head/first-tail allocations on the normal vmemmap allocation path, while preserving the existing page reference for reused DAX tail mappings. Signed-off-by: Muchun Song Acked-by: Qi Zheng --- v6: - Clarify that the DAX flag is renamed and used on additional paths (suggested by David Hildenbrand) - Make flags const and move it to the top of the function (suggested by David Hildenbrand) v3: - Update the subject and commit message to use compound page order terminology v2: - Collect Acked-by from Qi Zheng --- mm/sparse-vmemmap.c | 27 +++++++++++++++------------ 1 file changed, 15 insertions(+), 12 deletions(-) diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index f77e6e1e5a8b..b4b72f233bf6 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -35,8 +35,8 @@ /* * Flags for vmemmap_populate_range and friends. */ -/* Get a ref on the head page struct page, for ZONE_DEVICE compound pages */ -#define VMEMMAP_POPULATE_PAGEREF 0x0001 +/* Vmemmap population for ZONE_DEVICE compound pages */ +#define VMEMMAP_POPULATE_DAX 0x0001 #include "internal.h" #include "mm_init.h" @@ -247,13 +247,17 @@ static inline struct page *vmemmap_shared_tail_page(unsigned int order, #endif static __meminit void *vmemmap_alloc_pte(unsigned long pfn, int node, - struct vmem_altmap *altmap) + struct vmem_altmap *altmap, unsigned long flags) { struct zone *zone; struct page *page; const unsigned int order = pfn_to_section_compound_order(pfn); - if (!vmemmap_optimizable_pfn(pfn)) + /* + * Device DAX still relies on vmemmap_populate_compound_pages() for + * head/first-tail allocation and tail-page reuse. + */ + if (!vmemmap_optimizable_pfn(pfn) || flags & VMEMMAP_POPULATE_DAX) return vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); zone = pfn_to_zone(pfn, node); @@ -275,7 +279,7 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in pte_t entry; if (ptpfn == (unsigned long)-1) { - void *p = vmemmap_alloc_pte(pfn, node, altmap); + void *p = vmemmap_alloc_pte(pfn, node, altmap, flags); if (!p) return NULL; @@ -290,7 +294,7 @@ static pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, in * and through vmemmap_populate_compound_pages() when * slab is available. */ - if (flags & VMEMMAP_POPULATE_PAGEREF) + if (flags & VMEMMAP_POPULATE_DAX) get_page(pfn_to_page(ptpfn)); } entry = pfn_pte(ptpfn, PAGE_KERNEL); @@ -547,6 +551,7 @@ static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, unsigned long end, int node, struct dev_pagemap *pgmap) { + const unsigned long flags = VMEMMAP_POPULATE_DAX; unsigned long size, addr; pte_t *pte; int rc; @@ -561,8 +566,7 @@ static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, * with just tail struct pages. */ return vmemmap_populate_range(start, end, node, NULL, - pte_pfn(ptep_get(pte)), - VMEMMAP_POPULATE_PAGEREF); + pte_pfn(ptep_get(pte)), flags); } size = min(end - start, pgmap_vmemmap_nr(pgmap) * sizeof(struct page)); @@ -570,13 +574,13 @@ static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, unsigned long next, last = addr + size; /* Populate the head page vmemmap page */ - pte = vmemmap_populate_address(addr, node, NULL, -1, 0); + pte = vmemmap_populate_address(addr, node, NULL, -1, flags); if (!pte) return -ENOMEM; /* Populate the tail pages vmemmap page */ next = addr + PAGE_SIZE; - pte = vmemmap_populate_address(next, node, NULL, -1, 0); + pte = vmemmap_populate_address(next, node, NULL, -1, flags); if (!pte) return -ENOMEM; @@ -586,8 +590,7 @@ static int __meminit vmemmap_populate_compound_pages(unsigned long start_pfn, */ next += PAGE_SIZE; rc = vmemmap_populate_range(next, last, node, NULL, - pte_pfn(ptep_get(pte)), - VMEMMAP_POPULATE_PAGEREF); + pte_pfn(ptep_get(pte)), flags); if (rc) return -ENOMEM; } -- 2.54.0