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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44FC0EE49A0 for ; Mon, 21 Aug 2023 20:08:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230312AbjHUUII (ORCPT ); Mon, 21 Aug 2023 16:08:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230308AbjHUUIG (ORCPT ); Mon, 21 Aug 2023 16:08:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 50938E4 for ; Mon, 21 Aug 2023 13:08:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E3614649D9 for ; Mon, 21 Aug 2023 20:08:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 46BC9C433CC; Mon, 21 Aug 2023 20:08:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1692648483; bh=GUSAxjiit/ZgxptDqu8FnYjwksVzcn0OybqLgAv6y5E=; h=Date:To:From:Subject:From; b=xcwn9FaOta+UBdhxfi+ctrzC2MnIdLHBQez1jijZ9xzOlkjR4/x9obed4bCh9QuEH gimNCBB6o5LlmA4iwXFptdb93Moc4ULoTk7wCNT0Rkg+cAi8XBA4oFUQSnVLPb95C+ mIAiSvOSUDIkapZTaC5bYdOlNxoJq9hTNJL/ZWbE= Date: Mon, 21 Aug 2023 13:08:02 -0700 To: mm-commits@vger.kernel.org, willy@infradead.org, torvalds@linux-foundation.org, shuah@kernel.org, peterx@redhat.com, pbonzini@redhat.com, mgorman@techsingularity.net, mgorman@suse.de, liubo254@huawei.com, jhubbard@nvidia.com, jgg@ziepe.ca, hughd@google.com, david@redhat.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] smaps-use-vm_normal_page_pmd-instead-of-follow_trans_huge_pmd.patch removed from -mm tree Message-Id: <20230821200803.46BC9C433CC@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd() has been removed from the -mm tree. Its filename was smaps-use-vm_normal_page_pmd-instead-of-follow_trans_huge_pmd.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: David Hildenbrand Subject: smaps: use vm_normal_page_pmd() instead of follow_trans_huge_pmd() Date: Thu, 3 Aug 2023 16:32:03 +0200 We shouldn't be using a GUP-internal helper if it can be avoided. Similar to smaps_pte_entry() that uses vm_normal_page(), let's use vm_normal_page_pmd() that similarly refuses to return the huge zeropage. In contrast to follow_trans_huge_pmd(), vm_normal_page_pmd(): (1) Will always return the head page, not a tail page of a THP. If we'd ever call smaps_account with a tail page while setting "compound = true", we could be in trouble, because smaps_account() would look at the memmap of unrelated pages. If we're unlucky, that memmap does not exist at all. Before we removed PG_doublemap, we could have triggered something similar as in commit 24d7275ce279 ("fs/proc: task_mmu.c: don't read mapcount for migration entry"). This can theoretically happen ever since commit ff9f47f6f00c ("mm: proc: smaps_rollup: do not stall write attempts on mmap_lock"): (a) We're in show_smaps_rollup() and processed a VMA (b) We release the mmap lock in show_smaps_rollup() because it is contended (c) We merged that VMA with another VMA (d) We collapsed a THP in that merged VMA at that position If the end address of the original VMA falls into the middle of a THP area, we would call smap_gather_stats() with a start address that falls into a PMD-mapped THP. It's probably very rare to trigger when not really forced. (2) Will succeed on a is_pci_p2pdma_page(), like vm_normal_page() Treat such PMDs here just like smaps_pte_entry() would treat such PTEs. If such pages would be anonymous, we most certainly would want to account them. (3) Will skip over pmd_devmap(), like vm_normal_page() for pte_devmap() As noted in vm_normal_page(), that is only for handling legacy ZONE_DEVICE pages. So just like smaps_pte_entry(), we'll now also ignore such PMD entries. Especially, follow_pmd_mask() never ends up calling follow_trans_huge_pmd() on pmd_devmap(). Instead it calls follow_devmap_pmd() -- which will fail if neither FOLL_GET nor FOLL_PIN is set. So skipping pmd_devmap() pages seems to be the right thing to do. (4) Will properly handle VM_MIXEDMAP/VM_PFNMAP, like vm_normal_page() We won't be returning a memmap that should be ignored by core-mm, or worse, a memmap that does not even exist. Note that while walk_page_range() will skip VM_PFNMAP mappings, walk_page_vma() won't. Most probably this case doesn't currently really happen on the PMD level, otherwise we'd already be able to trigger kernel crashes when reading smaps / smaps_rollup. So most probably only (1) is relevant in practice as of now, but could only cause trouble in extreme corner cases. Let's move follow_trans_huge_pmd() to mm/internal.h to discourage future reuse in wrong context. Link: https://lkml.kernel.org/r/20230803143208.383663-3-david@redhat.com Fixes: ff9f47f6f00c ("mm: proc: smaps_rollup: do not stall write attempts on mmap_lock") Signed-off-by: David Hildenbrand Acked-by: Mel Gorman Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: John Hubbard Cc: Linus Torvalds Cc: liubo Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Paolo Bonzini Cc: Peter Xu Cc: Shuah Khan Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 3 +-- include/linux/huge_mm.h | 3 --- mm/internal.h | 7 +++++++ 3 files changed, 8 insertions(+), 5 deletions(-) --- a/fs/proc/task_mmu.c~smaps-use-vm_normal_page_pmd-instead-of-follow_trans_huge_pmd +++ a/fs/proc/task_mmu.c @@ -587,8 +587,7 @@ static void smaps_pmd_entry(pmd_t *pmd, bool migration = false; if (pmd_present(*pmd)) { - /* FOLL_DUMP will return -EFAULT on huge zero page */ - page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP); + page = vm_normal_page_pmd(vma, addr, *pmd); } else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) { swp_entry_t entry = pmd_to_swp_entry(*pmd); --- a/include/linux/huge_mm.h~smaps-use-vm_normal_page_pmd-instead-of-follow_trans_huge_pmd +++ a/include/linux/huge_mm.h @@ -25,9 +25,6 @@ static inline void huge_pud_set_accessed #endif vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf); -struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, - unsigned long addr, pmd_t *pmd, - unsigned int flags); bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long next); int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t *pmd, --- a/mm/internal.h~smaps-use-vm_normal_page_pmd-instead-of-follow_trans_huge_pmd +++ a/mm/internal.h @@ -924,6 +924,13 @@ int migrate_device_coherent_page(struct struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags); int __must_check try_grab_page(struct page *page, unsigned int flags); +/* + * mm/huge_memory.c + */ +struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmd, + unsigned int flags); + enum { /* mark page accessed */ FOLL_TOUCH = 1 << 16, _ Patches currently in -mm which might be from david@redhat.com are kvm-explicitly-set-foll_honor_numa_fault-in-hva_to_pfn_slow.patch mm-gup-dont-implicitly-set-foll_honor_numa_fault.patch pgtable-improve-pte_protnone-comment.patch selftest-mm-ksm_functional_tests-test-in-mmap_and_merge_range-if-anything-got-merged.patch selftest-mm-ksm_functional_tests-add-prot_none-test.patch selftest-mm-ksm_functional_tests-add-prot_none-test-fix.patch mm-swap-stop-using-page-private-on-tail-pages-for-thp_swap.patch mm-swap-inline-folio_set_swap_entry-and-folio_swap_entry.patch mm-huge_memory-work-on-folio-swap-instead-of-page-private-when-splitting-folio.patch