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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 26E0EC43602 for ; Wed, 8 Jul 2026 03:11:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ziyOxc8kPU1zkWqQd/xo7T152fH4QK1CRdbLsKeEh/w=; b=al/4Qf52Kekx+yPn1x7YXlxWL+ tfQ+v+KYNtrsuP3Zel1KIOUGAAAgOsFcBacQfUHa0KCjSlNs9pty1erNEGEYfo/2FfNnZQHmovskP K8xSnco+3cPnvvPOqsNUgWqS2wqq3AMTpiOLjBbIcFYX8symOAFE9G6X6L9+zKISzo0nCLqAa92u+ NtgIbl5PX8lkBmEWv7U550pf5q0dBetQnyrJCCKR+Ij1RYayagy29sVsFMUtsUjC8NAdFGeRlbb7t qYPKjcspQusInOQHN7Pj/5kvePmkosJ7M/IjUXN0EUr7FjPHwJtrI8urLlms1mhipKRrlNPpNsLxK q4hmNcaw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whIhO-0000000GCCo-0GKT; Wed, 08 Jul 2026 03:11:46 +0000 Received: from mail-pl1-x649.google.com ([2607:f8b0:4864:20::649]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1whIhF-0000000GC6b-2xxx for linux-arm-kernel@lists.infradead.org; Wed, 08 Jul 2026 03:11:40 +0000 Received: by mail-pl1-x649.google.com with SMTP id d9443c01a7336-2ca0481106cso3703575ad.0 for ; Tue, 07 Jul 2026 20:11:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1783480297; x=1784085097; darn=lists.infradead.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ziyOxc8kPU1zkWqQd/xo7T152fH4QK1CRdbLsKeEh/w=; b=VgGZZzCCPtbTGMyKo4OBI/sleFQfnrH8nUnaC8ggYCRrtkscer5yQMCqwD7KZ0nrjI cLCMoRAwgsnpwoOY3J1brZvr/fBQ7efgxUySmXpB1dqezlV7wG7TsE9sys4+qMP+ylju rKmRhncVQI+z+Ybk6EcJr4iXr9ui8K0CFOKe8tIiP5GqVS8WedwLeH61xFk86HL2x8o2 GJC/jUpeQlozyXl4OtFdkFDa2kNlN0Y9YJ8CJnfObpy7IfyC008oGKFC0k5qewe9qVrG q8c5oAELV+SgtiKVvFs1FcRWm+rOOUGf2QlFC/bBM3TTCJMO4Ee/vQyh+JidIagksUUY rEsw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783480297; x=1784085097; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=ziyOxc8kPU1zkWqQd/xo7T152fH4QK1CRdbLsKeEh/w=; b=nDaYbERLhF5slO6TSf578XalZQHfzbPUuqsCkmph3u1h8FhuWvf0tQdW5m9tLiyy5b SMDSH44VqV42Tks2dKYnKGUlOvsF3Yfd/AUZ7/axxPHb2FZlRLu9shh02oo8vWLGMDl9 4cG0Ygn6XKDAy86tPghDs5dwd+erTJm5/2Xffgt1j01B2qAkVlHIwwbhdluYP9C0n0IW 648C9yUyxCuPSmTKGgKvpw7xdjcZPvuCioVi3uqtAR4l+KLMGIO0D0tGhSUrY9D3xq6q 4WlbHl9KXF5+ryR+X6PA5VT69i18CasFzIK852vpQTfFikq9QuPn68hRnt3X5ZP2nhHT jIOQ== X-Forwarded-Encrypted: i=1; AHgh+Roa36UZyplIHglKbBvWuxhKAsZsSHElLfVyo1ouspSGzoB+6jDAz5YqK25JzypctIZ8Zo+nMNCoMJzYRt+MElow@lists.infradead.org X-Gm-Message-State: AOJu0YxRBil7P31XLei8RuXni5XhpY8Fp+0OuukMUShLKp6RYbCSZtgm wa3vGk4k57f155foxHALSSWpZ/qYEFUAuDfRNJVxzuari7MyAdmk5QTEhwDGepiyjXDb7SNYnnf 3x1CpoQ13QJo4DTH4iiNCvA== X-Received: from plbkv5.prod.google.com ([2002:a17:903:28c5:b0:2ca:d66c:97b2]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:1c9:b0:2cc:86a9:ebfb with SMTP id d9443c01a7336-2ccea47c361mr7188645ad.33.1783480296362; Tue, 07 Jul 2026 20:11:36 -0700 (PDT) Date: Wed, 8 Jul 2026 03:11:13 +0000 In-Reply-To: <20260708031129.3503195-1-jthoughton@google.com> Mime-Version: 1.0 References: <20260708031129.3503195-1-jthoughton@google.com> X-Mailer: git-send-email 2.55.0.795.g602f6c329a-goog Message-ID: <20260708031129.3503195-4-jthoughton@google.com> Subject: [PATCH 03/18] hugetlb_vmemmap: Leave pages partially HVOed upon restore failure From: James Houghton To: Will Deacon , Catalin Marinas , Muchun Song , Oscar Salvador Cc: Nikos Nikoleris , Linu Cherian , Mark Rutland , David Hildenbrand , Andrew Morton , Ryan Roberts , Nanyong Sun , Yu Zhao , Frank van der Linden , David Rientjes , James Houghton , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260707_201137_833173_18E64D10 X-CRM114-Status: GOOD ( 22.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Right now it is assumed that the restore routine in vmemmap_remap_free() will not fail; that is, if we fail to fully optimize a folio, it is assumed that restoring the folio to its pre-HVO state is guaranteed to succeed. Although vmemmap restoration may never fail in practice, properly handle such failure cases now. This will leave folios in a partially HVOed state. In a follow-up patch, failure certainly becomes possible. In the event we end up with partially-HVOed folios, make sure to: 1. Leave the HVO page flag in place. 2. Free any unused vmemmap pages. Always pass the vmemmap_tail page to the restore routine to avoid leaking the non-optimized vmemmap pages for a partially HVOed page. Signed-off-by: James Houghton --- mm/hugetlb_vmemmap.c | 49 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 38 insertions(+), 11 deletions(-) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index 8d4e8ee51fdd..5fee01bf5b34 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -236,12 +236,15 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, { struct page *src = pte_page(ptep_get(pte)), *dst; + if (WARN_ON_ONCE(!walk->vmemmap_tail)) + return; + /* - * When rolling back vmemmap_remap_free(), keep the copied head page + * When restoring a partially-HVOed page, keep the copied head page * mapping and restore only PTEs currently pointing at the shared tail * page. */ - if (walk->vmemmap_tail && walk->vmemmap_tail != src) + if (walk->vmemmap_tail != src) return; VM_WARN_ON_ONCE(PageHead((const struct page *)addr)); @@ -277,6 +280,7 @@ static int vmemmap_remap_split(unsigned long start, unsigned long end) return vmemmap_remap_range(start, end, &walk); } +static const int VMEMMAP_REMAP_INCOMPLETE = 1; /** * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end) * to use @vmemmap_head/tail, then free vmemmap which @@ -291,7 +295,8 @@ static int vmemmap_remap_split(unsigned long start, unsigned long end) * responsibility to free pages. * @flags: modifications to vmemmap_remap_walk flags * - * Return: %0 on success, negative error code otherwise. + * Return: %0 on success, VMEMMAP_REMAP_INCOMPLETE if the page is incompletely + * optimized, negative error code otherwise. */ static int vmemmap_remap_free(unsigned long start, unsigned long end, struct page *vmemmap_head, @@ -326,7 +331,8 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end, .flags = 0, }; - vmemmap_remap_range(start, end, &walk); + if (vmemmap_remap_range(start, end, &walk)) + return VMEMMAP_REMAP_INCOMPLETE; return ret; } @@ -385,6 +391,8 @@ static struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end) * to the page which is from the @vmemmap_pages * respectively. + * @h: the hstate for the folio whose vmemmap is getting remapped + * @folio: the folio whose vmemmap is getting remapped * @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 @@ -393,20 +401,35 @@ static struct page *vmemmap_get_tail(unsigned int order, struct zone *zone) * * Return: %0 on success, negative error code otherwise. */ -static int vmemmap_remap_alloc(unsigned long start, unsigned long end, +static int vmemmap_remap_alloc(const struct hstate *h, struct folio *folio, + unsigned long start, unsigned long end, unsigned long flags) { LIST_HEAD(vmemmap_pages); - struct vmemmap_remap_walk walk = { + struct vmemmap_remap_walk walk; + struct page *vmemmap_tail; + int ret; + + vmemmap_tail = vmemmap_get_tail(h->order, folio_zone(folio)); + if (WARN_ON_ONCE(!vmemmap_tail)) + return -ENOMEM; + + if (alloc_vmemmap_page_list(start, end, &vmemmap_pages)) + return -ENOMEM; + + walk = (struct vmemmap_remap_walk) { .remap_pte = vmemmap_restore_pte, + .vmemmap_tail = vmemmap_tail, .vmemmap_pages = &vmemmap_pages, .flags = flags, }; - if (alloc_vmemmap_page_list(start, end, &vmemmap_pages)) - return -ENOMEM; + ret = vmemmap_remap_range(start, end, &walk); - return vmemmap_remap_range(start, end, &walk); + /* Not all pages may have been consumed */ + free_vmemmap_page_list(&vmemmap_pages); + + return ret; } static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON); @@ -439,7 +462,7 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h, * When a HugeTLB page is freed to the buddy allocator, previously * discarded vmemmap pages must be allocated and remapping. */ - ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, flags); + ret = vmemmap_remap_alloc(h, folio, vmemmap_start, vmemmap_end, flags); if (!ret) folio_clear_hugetlb_vmemmap_optimized(folio); @@ -572,7 +595,11 @@ static int __hugetlb_vmemmap_optimize_folio(const struct hstate *h, vmemmap_head, vmemmap_tail, vmemmap_pages, flags); out: - if (ret) + /* + * If ret == VMEMMAP_REMAP_INCOMPLETE, the folio might be partially + * HVOed. Leave the HVO page folio flag in place. + */ + if (ret < 0) folio_clear_hugetlb_vmemmap_optimized(folio); return ret; -- 2.55.0.795.g602f6c329a-goog