From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794023620; b=Yk4z3OOXpqOfE3MVhaaEfrRKD7EPrXpfXHiggkm/LtSatJYIVsvzGG52pAxYg3/6xksH /5g0yOjqMGff+MtB5gaXUm89LM/qiIndMPmRpVNVFSnI+gYXFuoJ4UOPEwSKE7zYne4Qo bep3hdJlQRzA5RKHgxgFDM16C7j+EieOdDK2yr00F6E0j9xXYVxH3OYppZy7lt5g9pBt4 N7Ro7qM7OCGRynmuEiwAB7Qn1MyEc+Pv4FFOz04Jqb8TKlTTsb91bdTYJejNEHIWcFXae ktp4zal9I4/o7+rh8CEXsQpp9ibhUdxGkGiH17Pet+QUTigr7qyfjvXykzpdn9rvpIw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794023620; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=RumzGO0/+pT/BfdkHkIgLmgp4m5ZJqR22B5vyrghWak=; b=DjDXK2j5q2CSr6tUXgFt+MAzVDuFhgjvk5AJPCpZs4AfvsV3oLZFDC1anzKV4pEQa1MZ cvGUL06PinDlzsyDpiWwoSGWQmCU+Xo6Ln+S5vMqr6lCY0U30E5HHKpVR1B6BxOe+heHp POicTUrVeWqaTcxhowYO2DxmKK1AsD9KBb4ODfq1GodCBPPqf+Nk1cjwWj+fJDmAUEnvp iM0LAWOgl5ODoVWgZP+uiSU8ohI6gkuvbX6225VmuS0CcvAt2mwJ5h4BW55nIJRAR17fL Y8gjdHOyVVV70z9SrTNppSbUCseo1vjgC4RSItfeAs4HBCwNpwj4EdPhAahNQvxlJDQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=vN4NfbCX; 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 A626D606A330 for ; Sat, 7 Nov 2026 03:53:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=vN4NfbCX Received: by smtp.kernel.org (Postfix) with ESMTPSA id 717961F008A2; Sat, 7 Nov 2026 03:53:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1794023619; bh=RumzGO0/+pT/BfdkHkIgLmgp4m5ZJqR22B5vyrghWak=; h=Date:To:From:Subject; b=vN4NfbCXQT+WGDM0sOzJQde5NUPvvCsCuiy3GWaSACtAFghNkK0guzR1f34u9Cn/9 wiudhWYg7HIdKVeFel/9HGjngDohYj1zU9YHoUsQPKgINzgNjlJgfoNpikNa7kf3OB Hmxru3hsQ2Ur2fa2AJp5Qu22YbGownzD4xTb/OkM= Date: Fri, 06 Nov 2026 19:53:39 -0800 To: mm-commits@vger.kernel.org,muchun.song@linux.dev,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-hugetlb_vmemmap-simplify-vmemmap-head-page-handling.patch added to mm-unstable branch Message-Id: <20261107035339.717961F008A2@smtp.kernel.org> X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list The patch titled Subject: mm: hugetlb_vmemmap: simplify vmemmap head page handling has been added to the -mm mm-unstable branch. Its filename is mm-hugetlb_vmemmap-simplify-vmemmap-head-page-handling.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb_vmemmap-simplify-vmemmap-head-page-handling.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Muchun Song Subject: mm: hugetlb_vmemmap: simplify vmemmap head page handling Date: Sat, 07 Nov 2026 10:27:47 +0800 The new head page is already tracked on the vmemmap page list before remapping starts. Passing it separately gives the remap walker two ways to refer to the same page and unnecessarily complicates its interface. Use the page list as the single handoff mechanism for the head page, removing the redundant state from the walker. No functional change intended. Link: https://lore.kernel.org/20261107022756.77731-5-songmuchun@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Andrew Morton Reviewed-by: Lance Yang Reviewed-by: Qi Zheng Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Oscar Salvador Tested-by: Andrew Morton Cc: James Houghton Cc: David Hildenbrand Cc: Yili Zhang Cc: Kiryl Shutsemau Cc: "Oscar Salvador (SUSE)" Cc: Huacai Chen --- mm/hugetlb_vmemmap.c | 30 +++++++++++++----------------- 1 file changed, 13 insertions(+), 17 deletions(-) --- a/mm/hugetlb_vmemmap.c~mm-hugetlb_vmemmap-simplify-vmemmap-head-page-handling +++ a/mm/hugetlb_vmemmap.c @@ -25,10 +25,9 @@ * * @remap_pte: called for each lowest-level entry (PTE). * @nr_walked: the number of walked pte. - * @vmemmap_head: the page to be installed as first in the vmemmap range * @vmemmap_tail: the page to be installed as non-first in the vmemmap range - * @vmemmap_pages: the list head of the vmemmap pages that can be freed - * or is mapped from. + * @vmemmap_pages: list supplying replacement pages for the remap and + * receiving displaced backing pages for the caller to free. * @flags: used to modify behavior in vmemmap page table walking * operations. */ @@ -37,7 +36,6 @@ struct vmemmap_remap_walk { struct vmemmap_remap_walk *walk); unsigned long nr_walked; - struct page *vmemmap_head; struct page *vmemmap_tail; struct list_head *vmemmap_pages; @@ -208,10 +206,13 @@ static void vmemmap_remap_pte(pte_t *pte pte_t entry; /* Remapping the head page requires r/w */ - if (unlikely(walk->nr_walked == 0 && walk->vmemmap_head)) { + if (unlikely(walk->nr_walked == 0)) { + struct page *head; + VM_WARN_ON_ONCE(!PageHead((const struct page *)addr)); - list_del(&walk->vmemmap_head->lru); + head = list_first_entry(walk->vmemmap_pages, struct page, lru); + list_del(&head->lru); /* * Makes sure that preceding stores to the page contents from @@ -220,7 +221,7 @@ static void vmemmap_remap_pte(pte_t *pte */ smp_wmb(); - entry = mk_pte(walk->vmemmap_head, PAGE_KERNEL); + entry = mk_pte(head, PAGE_KERNEL); } else { VM_WARN_ON_ONCE(!PageTail((const struct page *)addr)); @@ -284,23 +285,20 @@ static int vmemmap_remap_split(unsigned } /** - * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end) - * to use @vmemmap_head/tail, then free vmemmap which - * the range are mapped to. + * vmemmap_remap_free - remap a vmemmap range and collect old backing pages * @start: start address of the vmemmap virtual address range that we want * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. - * @vmemmap_head: the page to be installed as first in the vmemmap range * @vmemmap_tail: the page to be installed as non-first in the vmemmap range - * @vmemmap_pages: list to deposit vmemmap pages to be freed. It is callers - * responsibility to free pages. + * @vmemmap_pages: input/output list whose first entry supplies the new backing + * page for @start; replaced backing pages are added to the list for + * the caller to free. * @flags: modifications to vmemmap_remap_walk flags * * Return: %0 on success, negative error code otherwise. */ static int vmemmap_remap_free(unsigned long start, unsigned long end, - struct page *vmemmap_head, struct page *vmemmap_tail, struct list_head *vmemmap_pages, unsigned long flags) @@ -308,7 +306,6 @@ static int vmemmap_remap_free(unsigned l int ret; struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_remap_pte, - .vmemmap_head = vmemmap_head, .vmemmap_tail = vmemmap_tail, .vmemmap_pages = vmemmap_pages, .flags = flags, @@ -550,8 +547,7 @@ static int __hugetlb_vmemmap_optimize_fo * they can be freed by the caller. */ ret = vmemmap_remap_free(vmemmap_start, vmemmap_end, - vmemmap_head, vmemmap_tail, - vmemmap_pages, flags); + vmemmap_tail, vmemmap_pages, flags); out: if (ret) folio_clear_hugetlb_vmemmap_optimized(folio); _ Patches currently in -mm which might be from muchun.song@linux.dev are mm-fix-missing-page-table-destructor-in-pagetable_free.patch riscv-mm-fix-hotplug-page-table-destructor-handling.patch riscv-mm-fix-missing-destructor-for-hotplug-pud-tables.patch arm64-mm-fix-destructor-for-unconstructed-hotplug-page-tables.patch mm-sparse-vmemmap-map-shared-vmemmap-tail-pages-as-read-only.patch powerpc-mm-map-shared-vmemmap-tail-pages-as-read-only.patch mm-hugetlb_vmemmap-remove-vmemmap_wrprotect_hvo.patch mm-hugetlb_vmemmap-remove-hugetlb_vmemmap_optimize_bootmem_folios.patch mm-generalize-kernel-pte-table-allocation.patch mm-generalize-pmd-page-table-allocation.patch mm-generalize-pud-page-table-allocation.patch mm-remove-pagetable_dtor_free.patch mm-remove-redundant-pagetable_dtor-calls.patch mm-hugetlb_vmemmap-remove-hugetlb-specific-vmemmap-optimization-macros.patch mm-hugetlb_vmemmap-unify-vmemmap_splitremap_no_tlb_flush.patch mm-hugetlb_vmemmap-simplify-vmemmap-head-page-handling.patch mm-hugetlb_vmemmap-generalize-vmemmap-page-allocation.patch mm-hugetlb_vmemmap-unify-writable-vmemmap-page-preparation.patch mm-hugetlb_vmemmap-rename-vmemmap_remap_pte-to-vmemmap_optimize_pte.patch mm-hugetlb_vmemmap-simplify-shared-tail-page-handling.patch mm-hugetlb_vmemmap-move-alloc_vmemmap_page_list-next-to-its-free-helper.patch mm-hugetlb_vmemmap-make-vmemmap-optimization-folio-oriented.patch mm-hugetlb_vmemmap-make-vmemmap-restoration-folio-oriented.patch mm-hugetlb_vmemmap-unify-vmemmap-range-restoration.patch mm-hugetlb_vmemmap-make-vmemmap-pte-conversion-folio-oriented.patch mm-hugetlb-fix-validation-of-unsupported-hugetlb-orders.patch