From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 35E0830D40B; Thu, 16 Jul 2026 14:51:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784213490; cv=none; b=pJcDD3fzmHhhJpgSXAvssM08A3TPJUNZ7VbFmWfvnBbFhaA6/ryCwTMHWtqNp1SYbJYXuKdTcNmmKzqR7RonwGE0+xe+baIhha02wpe9fQWNlwWaJRIolxTMlnF9yv4Gzw/KhzR6/wlw5jDjqtCh1b/hlDuvIolllgw0fplY1N4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784213490; c=relaxed/simple; bh=62fkKqSyTuU705FaaEq0TAVQAMr3fBZklafAP9Jyqn4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=XmHrqBQIE27qN46INFhDpLMVsfz7zIp9K3cZPaPdubZmwFSiCUBqgYSCqjgeBGWnZIFiPD8yJHoVl1l7k2bFbSrheJY9rWTi4RVDYIf4V7upgfqBulGTS6fLuOUVoroGE6lA9lXywWhGelcEYSR1gTFpSp7sg+zM7oWO1KkaMZA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MVucWdgV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MVucWdgV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADE771F00A3E; Thu, 16 Jul 2026 14:51:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784213489; bh=lX1TFiP6xIbjy9evrHNZox00I5e7bkCckKcJldvVME4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=MVucWdgVB3uHkthYYg4NX8x7GsFBKVscGgVa3g/uHHXEAeYf8FperTLXsPRKNBKQI LS3dPrUJ+oFBauuHY6ef3I8QQjvOJTbNW8vccNpP5NVIMJy20MooRkImJnPP05FWKf CIp+s3x3F1p7sEeFYDWskJJ29o/iW6cB90NVqln618zouzDsORVOkljdc0vz90fGW3 CNNJEW8dY782Is74iDs02CzWGU5EfZUYJUrZ5xtYYAfLnk3IkN0UhUyUzk3NF73C2T wFLu1i0M9T6BMeh8DKIBHFtzPgPuMJDyhVi5QtsgC6iM6bAd3SIpxnp0onizUfxkLc 7YZV8IDYnrf2A== From: "David Hildenbrand (Arm)" Date: Thu, 16 Jul 2026 16:51:01 +0200 Subject: [PATCH v2 02/10] mm: provide free_reserved_pages(), removing x86 variant Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260716-bootmem_info_part2-v2-2-4afc76c73d61@kernel.org> References: <20260716-bootmem_info_part2-v2-0-4afc76c73d61@kernel.org> In-Reply-To: <20260716-bootmem_info_part2-v2-0-4afc76c73d61@kernel.org> To: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Muchun Song , Oscar Salvador Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.15.2 Let's extend free_reserved_page() in page_alloc.c to free_reserved_pages(), dropping the custom x86 variant. The common-code variant will consume an order, so adjust the x86 callers accordingly. Make free_reserved_pages() assume that we are freeing ordinary high-order pages, just with the special "reserved" flavor. The target use case for now is freeing vmemmap PMD pages. Set the refcount directly to 0 (instead of 1) and call __free_frozen_pages(). Set the page count to 0 before clearing PG_reserved, so someone checking PG_reserved (and not finding it set) to then try grabbing a ref would not suddenly have that ref be dropped. That is arguably cleaner and safer than the old way of doing it. Add some kerneldoc. Use a single adjust_managed_page_count() call. Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Muchun Song Signed-off-by: David Hildenbrand (Arm) --- arch/x86/mm/init_64.c | 8 +------- include/linux/mm.h | 8 ++++++-- mm/page_alloc.c | 33 ++++++++++++++++++++++++++------- 3 files changed, 33 insertions(+), 16 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 69e36f02a663a..320e742b0bb3f 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1000,12 +1000,6 @@ int arch_add_memory(int nid, u64 start, u64 size, return add_pages(nid, start_pfn, nr_pages, params); } -static void free_reserved_pages(struct page *page, unsigned long nr_pages) -{ - while (nr_pages--) - free_reserved_page(page++); -} - static void __meminit free_pagetable(struct page *page) { /* bootmem page has reserved flag */ @@ -1038,7 +1032,7 @@ static void __meminit free_vmemmap_pages(struct page *page, unsigned int order, while (nr_pages--) put_page_bootmem(page++); } else { - free_reserved_pages(page, nr_pages); + free_reserved_pages(page, order); } } else { __free_pages(page, order); diff --git a/include/linux/mm.h b/include/linux/mm.h index 113e1752548c2..62b261cccf16f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3993,8 +3993,12 @@ extern unsigned long free_reserved_area(void *start, void *end, extern void adjust_managed_page_count(struct page *page, long count); -/* Free the reserved page into the buddy system, so it gets managed. */ -void free_reserved_page(struct page *page); +void free_reserved_pages(struct page *page, unsigned int order); + +static inline void free_reserved_page(struct page *page) +{ + free_reserved_pages(page, 0); +} static inline void mark_page_reserved(struct page *page) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a63733dac659e..2e17243ff604f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6381,15 +6381,34 @@ void adjust_managed_page_count(struct page *page, long count) } EXPORT_SYMBOL(adjust_managed_page_count); -void free_reserved_page(struct page *page) +/** + * free_reserved_pages - free reserved pages + * @page: First page to free. + * @order: The page order to free. + * + * Free pages allocated through memblock during boot, letting the buddy + * manage them from now on. + * + * @page must be naturally aligned to the order and the order must not + * exceed MAX_PAGE_ORDER. All pages must be reserved. + */ +void free_reserved_pages(struct page *page, unsigned int order) { - clear_page_tag_ref(page); - ClearPageReserved(page); - init_page_count(page); - __free_page(page); - adjust_managed_page_count(page, 1); + const unsigned long nr_pages = 1UL << order; + int i; + + VM_WARN_ON_ONCE(!IS_ALIGNED(page_to_pfn(page), nr_pages)); + VM_WARN_ON_ONCE(order > MAX_PAGE_ORDER); + + for (i = 0; i < nr_pages; i++) { + clear_page_tag_ref(page + i); + set_page_count(page + i, 0); + ClearPageReserved(page + i); + } + adjust_managed_page_count(page, nr_pages); + __free_frozen_pages(page, order, FPI_NONE); } -EXPORT_SYMBOL(free_reserved_page); +EXPORT_SYMBOL(free_reserved_pages); static int page_alloc_cpu_dead(unsigned int cpu) { -- 2.43.0