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 40CAF1E492D; Tue, 7 Jul 2026 18:40:49 +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=1783449651; cv=none; b=ok+G/h+17wTw6KYhbfDpX0EuAmLagFVZ6Q5Q4ELrgbepZkdmuGd9QVnZmVA9K26KFYsjCQfwrVeUZpR4aXDTpEvJ28sE8K6z8LSksiUgdhpVFKA2Rn7aaGhbpvsRFtxsmPAcmMk1GlWySblM9QUcAdKazsPyXvoc4hjInFrQNYM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783449651; c=relaxed/simple; bh=TjQMtxEaIh7Q8zcox35Zn7MXyzl3+iW3bIrwTupcXZ0=; h=Date:To:From:Subject:Message-Id; b=NQ8QS48ixLfU6XGbfW1+WotFchIifGKR9TCCFtz9s0Ll+kcKagi3WyZcd8SYkHd+YTVLwDJh/8ZvnuxoDrBgTjZbCkCfxiFX2bUA+Kx/t3gzDdy7stjdqv+8040fw0qxDyyX3RX1+m3REAqf7Uhm1AfR22rtDLV5qVN33fZG8Z8= 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=h3Z2OGr9; 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="h3Z2OGr9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A05AC1F000E9; Tue, 7 Jul 2026 18:40:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1783449649; bh=XWbsn3FVZag358NDLdu64q0PSQ4ohzYrZW345Dw15Mo=; h=Date:To:From:Subject; b=h3Z2OGr9oF1hYHM4CSyjTEf0XNPLNna4NUu9fXr+Pkjv12JD0uwMu/rfi7uEYi3j5 hL+ohXju7L7/jA/MEWw2DLPkggAXcvTBDsiGoDny9DruTbjEFCvLJ2AWoNC/RqQMeU AG0+8knRvHNr0UbgEdk7SIVsQO4CqRviRJmm8BIY= Date: Tue, 07 Jul 2026 11:40:49 -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-unpopulated-ptes.patch added to mm-hotfixes-unstable branch Message-Id: <20260707184049.A05AC1F000E9@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 unpopulated ptes has been added to the -mm mm-hotfixes-unstable branch. Its filename is fs-proc-task_mmu-fix-pagemap_scan-written-state-for-unpopulated-ptes.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-unpopulated-ptes.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 unpopulated ptes Date: Tue, 7 Jul 2026 16:13:49 +0100 PAGEMAP_SCAN reports an unpopulated pte differently depending on which path serves the request. The PAGE_IS_WRITTEN fast path in pagemap_scan_pmd_entry() reports a pte_none as written (and, under PM_SCAN_WP_MATCHING, arms a marker); pagemap_page_category() returns 0 for the same pte_none. A request that cannot take the fast path (an extra category bit, category_anyof_mask or category_inverted) therefore reports the pte as clean and skips arming it. A range that was populated and then MADV_DONTNEED'd reads as written via one mask and clean via another, and in the latter case is not re-armed for the next round -- an incremental-dump consumer (e.g. CRIU) using a richer mask drops the zapped range and stops tracking writes to it. Report pte_none as written in pagemap_page_category() too. A pte_none carries no uffd-wp marker, i.e. it is not write-protected -- the same condition under which the present and swap cases already report PAGE_IS_WRITTEN. The fast path applies no VMA test, so neither does this. The hugetlb and fully-unpopulated-PMD (no page table) scans have no PAGE_IS_WRITTEN fast path, so they do not exhibit the per-entry divergence and are left unchanged. Add a pagemap_ioctl selftest that populates a range, drops it with MADV_DONTNEED, and checks that the fast path and the generic (category_anyof_mask) path both report every page written. Link: https://lore.kernel.org/20260707151349.92143-1-kirill@shutemov.name Fixes: 12f6b01a0bcb ("fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag") Signed-off-by: Kiryl Shutsemau Cc: Muhammad Usama Anjum 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 | 14 ++++ tools/testing/selftests/mm/pagemap_ioctl.c | 56 ++++++++++++++++++- 2 files changed, 67 insertions(+), 3 deletions(-) --- a/fs/proc/task_mmu.c~fs-proc-task_mmu-fix-pagemap_scan-written-state-for-unpopulated-ptes +++ a/fs/proc/task_mmu.c @@ -2432,8 +2432,18 @@ static unsigned long pagemap_page_catego { unsigned long categories; - if (pte_none(pte)) - return 0; + if (pte_none(pte)) { + /* + * An unpopulated pte carries no uffd-wp marker, i.e. it is not + * write-protected, the same condition under which the present + * and swap cases below report PAGE_IS_WRITTEN. Report it here + * too so this generic path agrees with the PAGE_IS_WRITTEN fast + * path in pagemap_scan_pmd_entry(), which reports pte_none as + * written and, under PM_SCAN_WP_MATCHING, arms a marker. The + * fast path applies no VMA test, so neither does this. + */ + return PAGE_IS_WRITTEN; + } if (pte_present(pte)) { struct page *page; --- a/tools/testing/selftests/mm/pagemap_ioctl.c~fs-proc-task_mmu-fix-pagemap_scan-written-state-for-unpopulated-ptes +++ a/tools/testing/selftests/mm/pagemap_ioctl.c @@ -1051,6 +1051,57 @@ static void test_simple(void) ksft_test_result(i == TEST_ITERATIONS, "Test %s\n", __func__); } +/* + * A range that was populated and then MADV_DONTNEED'd is genuine pte_none + * with no uffd-wp marker. Such a pte must read the same regardless of which + * PAGEMAP_SCAN path serves the request: both the PAGE_IS_WRITTEN fast path and + * the generic path (reached e.g. via category_anyof_mask) must report every + * page written. + */ +static void unpopulated_scan_test(void) +{ + int npages = 16, i; + long mem_size = npages * page_size; + struct page_region regions[16]; + long fast = 0, slow = 0, ret; + char *mem; + + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("%s mmap failed\n", __func__); + + wp_init(mem, mem_size); + + /* Populate, then drop: the ptes become pte_none without a marker. */ + memset(mem, 1, mem_size); + if (madvise(mem, mem_size, MADV_DONTNEED)) + ksft_exit_fail_msg("%s MADV_DONTNEED failed\n", __func__); + + /* Fast path: category_mask == return_mask == PAGE_IS_WRITTEN. */ + ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("%s fast scan failed\n", __func__); + for (i = 0; i < ret; i++) + fast += LEN(regions[i]); + + /* Generic path: same query expressed via category_anyof_mask. */ + ret = pagemap_ioctl(mem, mem_size, regions, npages, 0, 0, + 0, PAGE_IS_WRITTEN, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("%s generic scan failed\n", __func__); + for (i = 0; i < ret; i++) + slow += LEN(regions[i]); + + ksft_test_result(fast == npages && slow == npages, + "%s unpopulated ptes reported written by both paths (%ld, %ld of %d)\n", + __func__, fast, slow, npages); + + wp_free(mem, mem_size); + munmap(mem, mem_size); +} + int sanity_tests(void) { unsigned long long mem_size, vec_size; @@ -1559,7 +1610,7 @@ int main(int __attribute__((unused)) arg if (!hugetlb_setup_default(4)) ksft_print_msg("HugeTLB test will be skipped\n"); - ksft_set_plan(117); + ksft_set_plan(118); page_size = getpagesize(); hpage_size = read_pmd_pagesize(); @@ -1737,6 +1788,9 @@ int main(int __attribute__((unused)) arg /* 17. ZEROPFN tests */ zeropfn_tests(); + /* 18. Unpopulated pte scan-path consistency */ + unpopulated_scan_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