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 16D0BC98332 for ; Sat, 26 Sep 2026 10:41:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1F0396B009D; Sat, 26 Sep 2026 06:41:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1A1B46B009E; Sat, 26 Sep 2026 06:41:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0B9166B009F; Sat, 26 Sep 2026 06:41:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D10C96B009D for ; Sat, 26 Sep 2026 06:41:53 -0400 (EDT) Received: from smtpin23.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 574AB160864 for ; Sat, 26 Sep 2026 10:41:53 +0000 (UTC) X-FDA: 85255572906.23.E189867 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf05.hostedemail.com (Postfix) with ESMTP id 9ACFC100007 for ; Sat, 26 Sep 2026 10:41:51 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IgB7NcLq; spf=pass (imf05.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 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=1790419311; 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=KhsTvKQ2fnSXkbWyS/YqLnoRwyxqzmWUbttn/FRcKWI=; b=qMjc6gI+dutKcic7doBZjmxvEnF2AV/IopOxbR46uGvZqp5E2cIgOvChwm7QmOrabNnvAH Ka7DpBCfoy8WzOc62n2HGTIIQlFY/hbuFdq5x/pCf8IxCp2dL/yalCSgQlFRep1UvuT5Pj Sb5ntaWDJ+DJxMv7+UyEl+KzW+pcE14= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=IgB7NcLq; spf=pass (imf05.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 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=1790419311; b=JNkw3JgSLfP0/BNc8Uj2Z/3V6RKl69ZVLRtfAIwa/dP2VvxNetL219cAU1yzLI/BAfmZ0T Dte3N0GAYEKSer57da5SqUb4yr2o1JPMD3BzZEvF8OTmig6yMnPnpIOBoeX0VAyHkMA+eO tMrP0FUu41HMF/TkN+sZfZNJFBD3aGE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 42ACF6020C; Sat, 26 Sep 2026 10:41:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 911E71F00898; Sat, 26 Sep 2026 10:41:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790419311; bh=KhsTvKQ2fnSXkbWyS/YqLnoRwyxqzmWUbttn/FRcKWI=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=IgB7NcLqpIid5a7MCnUMmAaPtKTkayne8jLDSMRHZx1NqxEy28NQKIqqBrt0kwUsH b5E7ISJiho2wtth7t14TdP78Czhi0m2aaVU46ti3XZ2s9NiPIXuYIZqBI9IVeuFTAQ 3B4P2xm6hgkmMtW2iPxKpO7XQPj0CPKepn2CxcLChKM8IfWc8/V43sabGia/2CONjN vXJmFU8Aa2uEMCUpSKmgh6j/AZY30D2+sEBUaGhTNIceeWCrK216ttRkZ+8Ahs2ssF T+WlcsrVxx9rA21TPxnmq+NDdoRaXN3nmOOgJMBEaNx73SJSFKP7jBJVqMVLoEWGGx dttV6cWAoZV7A== From: "Lorenzo Stoakes (ARM)" Date: Sat, 26 Sep 2026 11:41:11 +0100 Subject: [PATCH v3 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: <20260926-map-private-dev-zero-v3-6-d4781e84ccfc@kernel.org> References: <20260926-map-private-dev-zero-v3-0-d4781e84ccfc@kernel.org> In-Reply-To: <20260926-map-private-dev-zero-v3-0-d4781e84ccfc@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=4165; i=ljs@kernel.org; h=from:subject:message-id; bh=1leVrHr0vQD42BeUriV2AqaMbiNFdZlxKm+PRWQ0Ih0=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLK2L/SREO95sLjfyzgrouFDrfeE3dqSro5pNZGzGZ9n+ FT4iJp0lLIwiHExyIopsjz/Ir4/SCRsXucFfzeYOaxMIEMYuDgFYCKKuxkZOiYvr8vK8imSqFlU 8UpTYW9Zeu+KjWL9Qe51bNZezl6cjAyPA00aN+Xd1r+4LaIrQa/NWK/2fU96h8VzkaOvGUwSvRk B X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 9ACFC100007 X-Rspam-User: X-Stat-Signature: u3f89gxikdt7tihig6ztw3ax8r9859z6 X-HE-Tag: 1790419311-382984 X-HE-Meta: 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 PkDe6aSj V9xo2d9lijnfvn39PYzWy2gNr4SNGIYX3WPHnJZcrr3KGeoF+6dLytPeBTsD4XxuETvPMy0zoXx1jIuBh+Hw429EbaqSQZKcp4Ta6/16+AWUmmqWP4joX0tPXa1E27T8MignUstp49J1A97q1bkD2aiTHqUjmy1xH8iLZlk/w2Kp8eUrS0ALP7THBxOzbM7iqf8rzwzYIATAejq6CbUvyg+pwGkUJ/EJ9FJqAxNU9tNzycCXsMMY8/D3CmhlgGwgKABX00hcV7j8l9cBwnfjMDhDpW8e8UD476tgbGebxR1BZOLs= 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. Acked-by: David Hildenbrand (Arm) 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