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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 724B2C79F82 for ; Tue, 8 Sep 2026 11:25:14 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5302D6B009D; Tue, 8 Sep 2026 07:25:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 4E0C76B009E; Tue, 8 Sep 2026 07:25:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E4E36B009F; Tue, 8 Sep 2026 07:25:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 016B46B009D for ; Tue, 8 Sep 2026 07:25:12 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D8EDFC0581 for ; Tue, 8 Sep 2026 11:25:11 +0000 (UTC) X-FDA: 85190363622.28.0BC8092 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id 1CFBB40002 for ; Tue, 8 Sep 2026 11:25:09 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XgmNxLy3; spf=pass (imf27.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788866710; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=om0np5kv2o7p4ujdr2YodlAc5O6JiCLsFWeQl7Rh24s=; b=IAOnmSP0LSkPDW9xnM6z6g0qnCKj5ucHmFXFTW698KmvJSn3jHrU6hPA1Tu6mB+r9P0te8 numFpdiHWwyhQVr17b3ClsgLt37/nSRZt30fMKuWxOOLMtME7FZUA3jvCq2zoVVVHF98vu T/R9rhglE0gRgr6Wu0/TeKlvNDwHXVM= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XgmNxLy3; spf=pass (imf27.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788866710; b=CPYLOT/fSgymasiiF5FNgJLg1OSoYPLEcUcvP7tTBQ/6AXdYxBkiKnohJEjiDmikXu180O Gk0oiz6qPDbpDfBuhAItt/Zi84I6HrRp25FA5lJeiGyWQAVsW6t9BIwrSkBRHp1xMLLXcZ 0GOsMdvaCjC3T0jBwnbFU/iKB6WtN9k= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0AF5543F8E; Tue, 8 Sep 2026 11:25:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7C87C1F00A3D; Tue, 8 Sep 2026 11:25:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788866708; bh=om0np5kv2o7p4ujdr2YodlAc5O6JiCLsFWeQl7Rh24s=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XgmNxLy3XXo6zJi+ipSK9/Kxq68nxv16sLLPsIcI4SUgz9twJMZI81MQ1uLL0ZcxC sd97Rux856rODIB4DkQj/J3btopjnfJz8KZCP9qLUOFtDQ2gQaa0TKT3NTVC4GBxU1 sI9BHcnkMlIEvT3Uq5LYGLwZs7FIfAp4e0w3RWiA0yOxITZIYl1/1TqH1gLG9liSBj Kb076kSuPDadjILy/hzduDtUlggkJN6sLYAXYVTZWNmCw9NK5UL2hwjZJMzMYTiv8Z l53JivNcQ3Y6aIvGa6Ww9F6P4pV3Nj1kltUc3JU6Apyk2SY5pGVVxBG5oH77ddyBC0 RtU5Qgx16whFQ== From: "Lorenzo Stoakes (ARM)" Date: Tue, 08 Sep 2026 12:23:43 +0100 Subject: [PATCH v2 6/6] tools/testing/selftests/mm: add MAP_PRIVATE-/dev/zero merge tests MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260908-map-private-dev-zero-v2-6-acc7b5625305@kernel.org> References: <20260908-map-private-dev-zero-v2-0-acc7b5625305@kernel.org> In-Reply-To: <20260908-map-private-dev-zero-v2-0-acc7b5625305@kernel.org> To: Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , David Hildenbrand , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , "Matthew Wilcox (Oracle)" , Jan Kara Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4111; i=ljs@kernel.org; h=from:subject:message-id; bh=3png0c8or7nYdCZx23lmGIGRrVIeUt4V+p87b2uuFI8=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLLmfyh8seHhftu6/WGcCu07NVd5JzsuVNKK1z46e9qze f6bWVjWd5SyMIhxMciKKbI8/yK+P0gkbF7nBX83mDmsTCBDGLg4BWAifVoM/3PfCx6wSxSaVbmk 7+bO4wwSV0UPetSq1M6ULVgWsuaT41aGfwpzf6lGe8wQfcrt4LPt3/Qizd8Nv+V/c+012bGWz6A mhwUA X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 1CFBB40002 X-Stat-Signature: za7mzo5hkce6mh7i1yux81sg5asta9c3 X-Rspam-User: X-HE-Tag: 1788866709-959910 X-HE-Meta: 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 Ick/w9i5 m6NEns+1Q74ijEIxrCRRtC0Sl7ttAhAvZL459qB5GJDKUKETXtOBfuEsxooIB/mbmgl4zdC0rd930qNmM9f2S53q3Tqu76r3ZOKXVqJVk3BB66vCMjt+8bBUDCNbkvibgOfAtk+FTxRGFtmiOyyUZQGCQ3LmdAfm1RCjm6cfrGSiDyCGJeVIMyJq03vOrrC7P6d0fB+qqf04inY3CrJnN8/IpLPRIPqEv+yRGoLobE8lJ5wNhL9kJJg8Kn0zYHuT/DlS0QxZ6j56Qr1X9d7HuhhZ8104m75/oD5Pd2RiJ+42c3lw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Assert that MAP_PRIVATE-mapped /dev/zero mappings behave like they are anonymous. Test both unfaulted and faulted/unfaulted merges with page offset 0 which would not merge if the mappings were treated as if they were file-backed. With the recent change that makes them behave as pure anonymous mappings, the merges should succeed as their page offsets are equal to their anonymous page offsets. Signed-off-by: Lorenzo Stoakes (ARM) --- tools/testing/selftests/mm/merge.c | 95 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) diff --git a/tools/testing/selftests/mm/merge.c b/tools/testing/selftests/mm/merge.c index 52b8727b6628..7dd2933417c1 100644 --- a/tools/testing/selftests/mm/merge.c +++ b/tools/testing/selftests/mm/merge.c @@ -1362,6 +1362,101 @@ TEST_F(merge, anon_and_page_offset_mismatch_memfd) ASSERT_EQ(procmap->query.vma_end, (unsigned long)ptr + 5 * page_size); } +TEST_F(merge, merge_map_private_dev_zero_unfaulted) +{ + struct procmap_fd *procmap = &self->procmap; + unsigned int page_size = self->page_size; + char *carveout = self->carveout; + char *ptr, *ptr2; + int fd_zero; + + if (access("/dev/zero", F_OK)) + SKIP(return, "No /dev/zero."); + fd_zero = open("/dev/zero", O_RDWR); + ASSERT_NE(fd_zero, -1); + + /* + * Map two MAP_PRIVATE-/dev/zero VMAs next to one another with offset 0 + * each. + * + * With these being made truly anonymous upon mapping, they will + * merge. If they were file-backed VMAs the page offsets would prevent + * the merge: + * + * |-----||------| |-------------| + * | ptr || ptr2 | -> | ptr | + * |-----||------| |-------------| + */ + ptr = mmap(carveout, 5 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + ptr2 = mmap(&carveout[5 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + close(fd_zero); + ASSERT_NE(ptr, MAP_FAILED); + ASSERT_NE(ptr2, MAP_FAILED); + + /* Assert that they merged. */ + 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 + 10 * page_size); +} + +TEST_F(merge, merge_map_private_dev_zero_faulted_unfaulted) +{ + struct procmap_fd *procmap = &self->procmap; + unsigned int page_size = self->page_size; + char *carveout = self->carveout; + char *ptr, *ptr2; + int fd_zero; + + if (access("/dev/zero", F_OK)) + SKIP(return, "No /dev/zero."); + fd_zero = open("/dev/zero", O_RDWR); + ASSERT_NE(fd_zero, -1); + + /* + * Map a MAP_PRIVATE mapping of /dev/zero with page offset 0, then fault + * it in: + * + * |-------------------------------| + * | faulted | + * |-------------------------------| + */ + ptr = mmap(carveout, 15 * page_size, PROT_READ | PROT_WRITE, + MAP_FIXED | MAP_PRIVATE, fd_zero, 0); + ASSERT_NE(ptr, MAP_FAILED); + memset(ptr, 'x', 15 * page_size); + + /* + * Unmap the middle: + * + * |---------| |---------| + * | faulted | | faulted | + * |---------| |---------| + */ + ASSERT_EQ(munmap(&ptr[5 * page_size], 5 * page_size), 0); + + /* + * Map in a new unfaulted mapping in the middle with page offset 0 - + * this should merge and would not if it were treated as a file rather + * than pure anon: + * + * |---------|-----------|---------| + * | faulted | unfaulted | faulted | + * |---------|-----------|---------| + */ + ptr2 = mmap(&carveout[5 * page_size], 5 * page_size, + PROT_READ | PROT_WRITE, MAP_FIXED | MAP_PRIVATE, + fd_zero, 0); + close(fd_zero); + ASSERT_NE(ptr2, MAP_FAILED); + + /* Assert that they merged. */ + 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 + 15 * page_size); +} + TEST_F(merge_with_fork, mremap_faulted_to_unfaulted_prev) { struct procmap_fd *procmap = &self->procmap; -- 2.55.0