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 D81BA26059D; Thu, 9 Jul 2026 03:10:21 +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=1783566623; cv=none; b=fwS6JqtXO6SwOy59LXiMYUCi4mNUOIzNZpOVGQylMHmlsQO7C3dPrnG6LFQlUeGUhd+LC+epRpGWiDesXEKyt5iYym8e9+qkGwi6rW2pUOnf9Rozs30jEiS0YKu4jo+e3L4T3SM5z3zATxp7V1XY8Jm/CRz7r79dmYi9CKb3bPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783566623; c=relaxed/simple; bh=w0qnoxzxPz/XGRVWn9LUKDhDy7amgL24ut0miz1g5Ew=; h=Date:To:From:Subject:Message-Id; b=RHfBktyMloa81FFL1QcQpl189dAyfBAPHlOf8fVYUPykTD2wDYBVwMFz5he2R/gCJBhFKZ4MERSZ95sIcMLQrARNYLBByP3UXeHJjohSC9LgKD5WIucNk5hMNP6sXrItKyMI90qXQ/vho89EO3bnlj8lJQ8rQJ9QeqNz7VDbbtI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=asXT1XUp; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="asXT1XUp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A21E71F000E9; Thu, 9 Jul 2026 03:10:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783566621; bh=1NoD8na8eno4wENLmxSy5bbAeBzzxTtq0MIxxYoV8ZY=; h=Date:To:From:Subject; b=asXT1XUpZzY+qjCjp7AOxKcqahe7t9cnyJ0xwKzUdG2UyHOcAPxIotEz1ZOcMAVBM IGIHcEWzdXYJaC1mIb8TcvQ8oNlbjp2TWFwWNPUJEphSEFLI8Id8xCvKDnEqFeecaw 1lWySlptaxiiYetV4ra5RBaQDe3BtCSY3FTsJZa4= Date: Wed, 08 Jul 2026 20:10:21 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,usama.anjum@collabora.com,surenb@google.com,stable@vger.kernel.org,shuah@kernel.org,rppt@kernel.org,pfalcato@suse.de,peterx@redhat.com,mhocko@suse.com,ljs@kernel.org,liam@infradead.org,jannh@google.com,david@kernel.org,kas@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: + fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes.patch added to mm-hotfixes-unstable branch Message-Id: <20260709031021.A21E71F000E9@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: fs/proc/task_mmu: fix PAGEMAP_SCAN written state for PMD holes has been added to the -mm mm-hotfixes-unstable branch. Its filename is fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes.patch This patch will later appear in the mm-hotfixes-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: "Kiryl Shutsemau (Meta)" Subject: fs/proc/task_mmu: fix PAGEMAP_SCAN written state for PMD holes Date: Wed, 8 Jul 2026 11:34:29 +0100 PAGEMAP_SCAN reports an unpopulated PTE in a uffd-wp VMA as written (pagemap_page_category() and the PAGE_IS_WRITTEN fast path), but a range with no page table at all -- a PMD hole -- is skipped. pagemap_scan_pte_hole() evaluates the hole against p->cur_vma_category, which pagemap_scan_test_walk() builds from only PAGE_IS_WPALLOWED and PAGE_IS_SOFT_DIRTY, so PAGE_IS_WRITTEN is never set: the hole is neither reported nor, under PM_SCAN_WP_MATCHING, armed. This is reachable. An anonymous THP is write-protected in place as a huge PMD (change_huge_pmd(), anon is not split), and a full-PMD MADV_DONTNEED clears it to pmd_none. A WP-async consumer such as CRIU then misses the 2MB drop -- the range is not reported written and the next incremental dump keeps stale data. (A file/shmem THP is split on write-protect, so a later DONTNEED leaves a populated page table of pte_none entries, which are already reported; only anon THP reaches the hole path.) Add PAGE_IS_WRITTEN to the categories evaluated for a hole in a non-hugetlb uffd-wp VMA, matching the pte_none handling in pagemap_page_category(). The existing PM_SCAN_WP_MATCHING path then also arms the range: uffd_wp_range() allocates the page table and installs markers under WP_UNPOPULATED, so the next scan sees it clean until re-written. hugetlb is excluded on purpose: an allocated-but-empty huge entry reads as not-written via pagemap_hugetlb_category(), so reporting an unallocated hugetlb hole (which also reaches this path) as written would be inconsistent within the same VMA. hugetlb hole handling is left as-is. Add a pagemap_ioctl selftest that forms an anon THP, drops it with MADV_DONTNEED and checks the resulting PMD hole is reported written. Link: https://lore.kernel.org/20260708103429.150655-1-kirill@shutemov.name Fixes: 2bad466cc9d9 ("mm/uffd: UFFD_FEATURE_WP_UNPOPULATED") Signed-off-by: Kiryl Shutsemau Cc: Muhammad Usama Anjum Cc: Peter Xu Cc: David Hildenbrand Cc: Jann Horn Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Pedro Falcato Cc: Peter Xu Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Assisted-by: Claude:claude-fable-5 Cc: Signed-off-by: Andrew Morton --- fs/proc/task_mmu.c | 25 +++++++ tools/testing/selftests/mm/pagemap_ioctl.c | 60 ++++++++++++++++++- 2 files changed, 82 insertions(+), 3 deletions(-) --- a/fs/proc/task_mmu.c~fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes +++ a/fs/proc/task_mmu.c @@ -3049,12 +3049,33 @@ static int pagemap_scan_pte_hole(unsigne { struct pagemap_scan_private *p = walk->private; struct vm_area_struct *vma = walk->vma; + unsigned long categories; int ret, err; - if (!vma || !pagemap_scan_is_interesting_page(p->cur_vma_category, p)) + if (!vma) return 0; - ret = pagemap_scan_output(p->cur_vma_category, p, addr, &end); + /* + * An unpopulated range with no page table -- e.g. a 2MB anon THP + * dropped via MADV_DONTNEED, which pagemap_page_category() never sees + * -- reads as written on a uffd-wp VMA, matching the pte_none case + * there. Reporting it also lets the PM_SCAN_WP_MATCHING arming below + * install markers (uffd_wp_range() allocates the page table under + * WP_UNPOPULATED), so the next scan sees it clean until re-written. + * + * hugetlb is excluded: an allocated-but-empty huge entry reads as + * not-written via pagemap_hugetlb_category(), so reporting an + * unallocated hugetlb hole as written here would be inconsistent + * within the same VMA. + */ + categories = p->cur_vma_category; + if (userfaultfd_wp(vma) && !is_vm_hugetlb_page(vma)) + categories |= PAGE_IS_WRITTEN; + + if (!pagemap_scan_is_interesting_page(categories, p)) + return 0; + + ret = pagemap_scan_output(categories, p, addr, &end); if (addr == end) return ret; --- a/tools/testing/selftests/mm/pagemap_ioctl.c~fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes +++ a/tools/testing/selftests/mm/pagemap_ioctl.c @@ -25,6 +25,10 @@ #include "kselftest.h" #include "hugepage_settings.h" +#ifndef MADV_COLLAPSE +#define MADV_COLLAPSE 25 +#endif + #define PAGEMAP_BITS_ALL (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \ PAGE_IS_FILE | PAGE_IS_PRESENT | \ PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \ @@ -1102,6 +1106,59 @@ static void unpopulated_scan_test(void) munmap(mem, mem_size); } +/* + * A 2MB anon THP dropped with MADV_DONTNEED leaves a pmd_none hole with no + * page table, which pagemap_page_category() never sees. PAGEMAP_SCAN must + * still report it as written on a uffd-wp VMA, via pagemap_scan_pte_hole(). + */ +static void unpopulated_thp_hole_test(void) +{ + long npages, written = 0, ret, i; + struct page_region regions[16]; + char *area, *mem; + + if (!hpage_size) { + ksft_test_result_skip("%s THP not supported\n", __func__); + return; + } + npages = hpage_size / page_size; + + /* Get a PMD-aligned range so the range can be a single THP. */ + area = mmap(NULL, 2 * hpage_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (area == MAP_FAILED) + ksft_exit_fail_msg("%s mmap failed\n", __func__); + mem = (char *)(((unsigned long)area + hpage_size - 1) & ~(hpage_size - 1)); + + memset(mem, 1, hpage_size); + if (madvise(mem, hpage_size, MADV_COLLAPSE) || + !check_huge_anon(mem, 1, hpage_size)) { + ksft_test_result_skip("%s could not form a THP\n", __func__); + munmap(area, 2 * hpage_size); + return; + } + + wp_init(mem, hpage_size); + + /* Drop the whole PMD: it is cleared to a pmd_none hole. */ + if (madvise(mem, hpage_size, MADV_DONTNEED)) + ksft_exit_fail_msg("%s MADV_DONTNEED failed\n", __func__); + + ret = pagemap_ioctl(mem, hpage_size, regions, 16, 0, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("%s scan failed\n", __func__); + for (i = 0; i < ret; i++) + written += LEN(regions[i]); + + ksft_test_result(written == npages, + "%s pmd-hole reported written (%ld of %ld)\n", + __func__, written, npages); + + wp_free(mem, hpage_size); + munmap(area, 2 * hpage_size); +} + int sanity_tests(void) { unsigned long long mem_size, vec_size; @@ -1610,7 +1667,7 @@ int main(int __attribute__((unused)) arg if (!hugetlb_setup_default(4)) ksft_print_msg("HugeTLB test will be skipped\n"); - ksft_set_plan(118); + ksft_set_plan(119); page_size = getpagesize(); hpage_size = read_pmd_pagesize(); @@ -1790,6 +1847,7 @@ int main(int __attribute__((unused)) arg /* 18. Unpopulated pte scan-path consistency */ unpopulated_scan_test(); + unpopulated_thp_hole_test(); close(pagemap_fd); ksft_finished(); _ Patches currently in -mm which might be from kas@kernel.org are mm-hugetlb-fix-swap-entry-corruption-when-clearing-uffd-wp-at-fork.patch fs-proc-task_mmu-fix-pagemap_scan-written-state-for-unpopulated-ptes.patch fs-proc-task_mmu-fix-pagemap_scan-written-state-for-pmd-holes.patch mm-decouple-protnone-helpers-from-config_numa_balancing.patch mm-rename-uffd-wp-pte-bit-macros-to-uffd.patch mm-rename-uffd-wp-pte-accessors-to-uffd.patch userfaultfd-test-uffd-vma-flags-through-the-vma_flags_t-api.patch mm-add-vm_uffd_rwp-vma-flag.patch mm-add-mm_cp_uffd_rwp-change_protection-flag.patch mm-preserve-rwp-marker-across-pte-rewrites.patch mm-handle-vm_uffd_rwp-in-khugepaged-rmap-and-gup.patch userfaultfd-add-uffdio_register_mode_rwp-and-uffdio_rwprotect-plumbing.patch mm-userfaultfd-add-rwp-fault-delivery-and-expose-uffdio_register_mode_rwp.patch mm-pagemap-add-page_is_accessed-for-rwp-tracking.patch userfaultfd-add-uffd_feature_rwp_async-for-async-fault-resolution.patch userfaultfd-add-uffdio_set_mode-for-runtime-sync-async-toggle.patch selftests-mm-add-userfaultfd-rwp-tests.patch documentation-userfaultfd-document-rwp-working-set-tracking.patch