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 E4AE842EED3; Mon, 20 Jul 2026 14:40:39 +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=1784558441; cv=none; b=o5GU+NkxQkJZvx4OLE0vn6hUpg2kGrISu1694z7pJdzfzL4V/6IN3LfR+UIZTMwE75l1LI41GGCsiUlYoW1oQ35I4u+6cKJsNLOs8TNj5KkSPsPOo3P4YTEmszplYzOeH+xyz1AOT8EHYQFzKVgiAVsC04mVkoX9Rk8OsRKGA+k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784558441; c=relaxed/simple; bh=01jUabKK64NHmCAfzlhC9tplycbpQo1xdwDkiXe4HZs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=N+0prCCS4pQPaOyo8+l0bjt7U3c+/vjQk7TdRFEnbA0Z9/zQVXT78H7FHRTEJIXPiqV4x0QKkbW3Te1+bdpz5p5gYxfVEjOD0aRE7DgvReAGUp9cFZjcWGCzfzOE19YV+pp9PV1dtImNOzB1lp0lAhViFVYeq4vbH+9hDY7e/jU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DBlFwrbc; 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="DBlFwrbc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0DFCE1F00A3D; Mon, 20 Jul 2026 14:40:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784558439; bh=TVlIRx355t0P5ERcL5Eqs6eD8BqACD3+tbQgzhdx6t4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=DBlFwrbcQK7NIHiOTWSbYwYx5vuMNdKkZ3yv+rVCQxXAy+IKejV9jI3sTSLGepXFb U3HlKRj2+VM4tWmW6bq5EL3xVNL9Gz3oAKq1pX2/mpBDJ5f9/rANd7OXK1PINS7xWs pvzDzPjpJFjBva2QRIKA13ESwBdRmoa+MF/W43r3mgDSc4mOCVvpS3JPZdPCdAgfXN USioCtYCaOZYrkCSxQmiOqz7XvgLf9awJ2sPjXnqK/fw2Whw2nZ1bk9BXVz9oVcQRG sDBgUuioIcSEVKamGn9uAZQ3OOazJJRM8peS+fTBK8HtpwcA8FDEMZ4iiiKzA/oNb0 h50qkc0wSdwPQ== From: "Lorenzo Stoakes (ARM)" Date: Mon, 20 Jul 2026 15:38:37 +0100 Subject: [PATCH v2 11/15] tools/testing/selftests/mm: test virtual page offset merge behaviour 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: <20260720-b4-scalable-cow-virt-pgoff-v2-11-2d549757a76f@kernel.org> References: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> In-Reply-To: <20260720-b4-scalable-cow-virt-pgoff-v2-0-2d549757a76f@kernel.org> To: Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , "Matthew Wilcox (Oracle)" , Jan Kara , Miaohe Lin , Naoya Horiguchi , Rik van Riel , Harry Yoo , Lance Yang , Kees Cook , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman Cc: "Lorenzo Stoakes (ARM)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2961; i=ljs@kernel.org; h=from:subject:message-id; bh=01jUabKK64NHmCAfzlhC9tplycbpQo1xdwDkiXe4HZs=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLijN6sLZ3ad7Lv8YRNe6fO/TBlWX/cZc++rGIN9Unz9 /86/COpvqOUhUGMi0FWTJHl+Rfx/UEiYfM6L/i7wcxhZQIZwsDFKQATabrE8E/rV852sxhLh/W1 UazLN4SzH1nNsO5N3PeCj9MW+Eu79ocx/A8xdszPMt5u8Vt330o7y/cB07dmPte1uNR1IsScg1P 7Mx8A X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 While maintaining virtual page offsets for VMAs has no impact for most merge cases, it does impact MAP_PRIVATE-mapped file-backed mappings which happen to have matching page offset but not matching virtual page offset. Assert this behaviour by attempting to map an unfaulted MAP_PRIVATE-memfd region with a faulted one with compatible file page offsets but incompatible virtual page offsets. Signed-off-by: Lorenzo Stoakes (ARM) --- tools/testing/selftests/mm/merge.c | 57 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/tools/testing/selftests/mm/merge.c b/tools/testing/selftests/mm/merge.c index 519e5ac02db7..c093e27d0aea 100644 --- a/tools/testing/selftests/mm/merge.c +++ b/tools/testing/selftests/mm/merge.c @@ -1305,6 +1305,63 @@ TEST_F(merge, merge_vmas_with_mseal) ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 2 * page_size); } +TEST_F(merge, virt_and_page_offset_mismatch_memfd) +{ + struct procmap_fd *procmap = &self->procmap; + unsigned int page_size = self->page_size; + char *carveout = self->carveout; + char *ptr, *ptr2; + int fd; + + /* Create a 10 page memfd descriptor. */ + fd = memfd_create("virt_page_offset_test", MFD_CLOEXEC); + ASSERT_NE(fd, -1); + ASSERT_EQ(ftruncate(fd, 10 * page_size), 0); + + /* Map a region using the memfd at page offset 0. */ + ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd, 0); + ASSERT_NE(ptr, MAP_FAILED); + + /* + * Map another separately, and fault in, at page offset 5: + * + * |-----------| |---------| + * | unfaulted | | faulted | + * |-----------| |---------| + */ + ptr2 = mmap(&carveout[10 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, + fd, 5 * page_size); + ASSERT_NE(ptr2, MAP_FAILED); + ptr2[0] = 'x'; + + /* + * Now move it in place: + * + * |----------| + * | | + * v | + * |-----------| |---------| + * | unfaulted | | faulted | + * |-----------| |---------| + * + * Because virtual page offset of the faulted region is now + * &carveout[10 * page_size], despite the two regions being mergeable + * due to file page offset, they are NOT mergeable due to virtual page + * offset. + */ + ptr2 = sys_mremap(ptr2, 5 * page_size, 5 * page_size, + MREMAP_MAYMOVE | MREMAP_FIXED, + &carveout[5 * page_size]); + ASSERT_NE(ptr2, MAP_FAILED); + + /* Assert that they did not merge. */ + ASSERT_TRUE(find_vma_procmap(procmap, ptr)); + ASSERT_EQ(procmap->query.vma_start, (unsigned long)ptr); + ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size); +} + TEST_F(merge_with_fork, mremap_faulted_to_unfaulted_prev) { struct procmap_fd *procmap = &self->procmap; -- 2.55.0