From nobody Sun Feb 8 05:35:11 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65F2EC77B7F for ; Thu, 18 May 2023 02:19:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229835AbjERCTB (ORCPT ); Wed, 17 May 2023 22:19:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229824AbjERCSr (ORCPT ); Wed, 17 May 2023 22:18:47 -0400 Received: from mail-qv1-xf34.google.com (mail-qv1-xf34.google.com [IPv6:2607:f8b0:4864:20::f34]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 024DC210C for ; Wed, 17 May 2023 19:18:46 -0700 (PDT) Received: by mail-qv1-xf34.google.com with SMTP id 6a1803df08f44-6238daae378so2863126d6.1 for ; Wed, 17 May 2023 19:18:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1684376325; x=1686968325; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=sKe+AGy/Knc6S6d8Do5DN/gqM9Uy00SAbxH28Kp1LUQ=; b=gpiRUjEC25YrRlvGt299DCLZarxkVMlPppBRMeGjpsXJgixg9Mf1V9AuFtBCGh5WIO zYyRiKyN25sNF/Dcpz8SONWOiUN5ginUd3c7nz+IsRYtc1emCT1YYGJXOzWz7hQjxiRf eGy+COuTrQdS11tlfAZg8TDkFkoBJhCtLoMlI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684376325; x=1686968325; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=sKe+AGy/Knc6S6d8Do5DN/gqM9Uy00SAbxH28Kp1LUQ=; b=jQIgLyjHPpSrl5Tu3QGr45g54zHi6eRFo3/EPi+Q4AFCNeQ/VgndEoU1lkL8kY9/8i CgHqcgoDcsoKjhrjMaLC+srrSQoY2kuPXIl2cSsCskVuit6U8GbqQtqnHF7tmz8YRP2m Yl07dFMBvVM47d/8R1MoSfISHp8xZ82MvKmmxzJNZo0e3kM5k6C7nyo6vu5PYgVuve6Y FuZogMVhqAi9N1YyMMg4SyAs9sHzhCTH64xe9XTQ665N6+/CNMP90R/d9lw8SS/QDilF 3OOOKUP9XQsmYkAXxCEamxpcMRgXC8HI2bBX8C8Vk1hFa9+4lWLwQ3JW4bpZZubMSpqo B6bA== X-Gm-Message-State: AC+VfDya4FtcQk93KGKmb3cEJ1yipYlZhjJQH+4vjZtbOec9xucMGGol 88Yrq8ZOZYvGIdZnG9evtzlGFXnOaOC5TqdFoz4= X-Google-Smtp-Source: ACHHUZ777yYcb28ukvf7wMe6arbQau3nQ7xByk5Y74MW/Ag+xPWbEEnjrqrm1N1GiSy28LtIBX+nRg== X-Received: by 2002:a05:6214:2349:b0:5e8:3496:e641 with SMTP id hu9-20020a056214234900b005e83496e641mr2657341qvb.13.1684376324809; Wed, 17 May 2023 19:18:44 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (129.239.188.35.bc.googleusercontent.com. [35.188.239.129]) by smtp.gmail.com with ESMTPSA id j13-20020a05620a000d00b007577ccf566asm85082qki.93.2023.05.17.19.18.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 May 2023 19:18:44 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" Subject: [PATCH RFC 1/4] mm/mremap: Optimize the start addresses in move_page_tables() Date: Thu, 18 May 2023 02:18:22 +0000 Message-ID: <20230518021825.712742-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog In-Reply-To: <20230518021825.712742-1-joel@joelfernandes.org> References: <20230518021825.712742-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Recently, we see reports [1] of a warning that triggers due to move_page_tables() doing a downward and overlapping move on a mutually-aligned offset within a PMD. By mutual alignment, I mean the source and destination addresses of the mremap are at the same offset within a PMD. This mutual alignment along with the fact that the move is downward is sufficient to cause a warning related to having an allocated PMD that does not have PTEs in it. This warning will only trigger when there is mutual alignment in the move operation. A solution, as suggested by Linus Torvalds [2], is to initiate the copy process at the PMD level whenever such alignment is present. Implementing this approach will not only prevent the warning from being triggered, but it will also optimize the operation as this method should enhance the speed of the copy process whenever there's a possibility to start copying at the PMD level. Some more points: a. The optimization can be done only when both the source and destination of the mremap do not have anything mapped below it up to a PMD boundary. I add support to detect that. b. #1 is not a problem for the call to move_page_tables() from exec.c as nothing is expected to be mapped below the source/destination. However, for non-overlapping mutually aligned moves as triggered by mremap(2), I added support for checking such cases. c. I currently only optimize for PMD moves, in the future I/we can build on this work and do PUD moves as well if there is a need for this. But I want to take it one step at a time. [1] https://lore.kernel.org/all/ZB2GTBD%2FLWTrkOiO@dhcp22.suse.cz/ [2] https://lore.kernel.org/all/CAHk-=3Dwhd7msp8reJPfeGNyt0LiySMT0egExx3TVZ= SX3Ok6X=3D9g@mail.gmail.com/ Signed-off-by: Joel Fernandes (Google) --- mm/mremap.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index 411a85682b58..d7ee3b20e170 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -478,6 +478,51 @@ static bool move_pgt_entry(enum pgt_entry entry, struc= t vm_area_struct *vma, return moved; } =20 +/* + * A helper to check if a previous mapping exists. Required for + * move_page_tables() and realign_addr() to determine if a previous mapping + * exists before we can do realignment optimizations. + */ +static bool check_addr_in_prev(struct vm_area_struct *vma, unsigned long a= ddr, + unsigned long mask) +{ + int addr_masked =3D addr & mask; + struct vm_area_struct *prev =3D NULL, *cur =3D NULL; + + /* If the masked address is within vma, there is no prev mapping of conce= rn. */ + if (vma->vm_start <=3D addr_masked) + return false; + + /* + * Attempt to find vma before prev that contains the address. + * On any issue, assume the address is within a previous mapping. + * @mmap write lock is held here, so the lookup is safe. + */ + cur =3D find_vma_prev(vma->vm_mm, vma->vm_start, &prev); + if (!cur || cur !=3D vma || !prev) + return true; + + /* The masked address fell within a previous mapping. */ + if (prev->vm_end > addr_masked) + return true; + + return false; +} + +/* Opportunistically realign to specified boundary for faster copy. */ +static void realign_addr(unsigned long *old_addr, struct vm_area_struct *o= ld_vma, + unsigned long *new_addr, struct vm_area_struct *new_vma, + unsigned long mask) +{ + if ((*old_addr & ~mask) && + (*old_addr & ~mask) =3D=3D (*new_addr & ~mask) && + !check_addr_in_prev(old_vma, *old_addr, mask) && + !check_addr_in_prev(new_vma, *new_addr, mask)) { + *old_addr =3D *old_addr & mask; + *new_addr =3D *new_addr & mask; + } +} + unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long old_addr, struct vm_area_struct *new_vma, unsigned long new_addr, unsigned long len, @@ -493,6 +538,10 @@ unsigned long move_page_tables(struct vm_area_struct *= vma, =20 old_end =3D old_addr + len; =20 + /* If possible, realign addresses to PMD boundary for faster copy. */ + if (len >=3D PMD_SIZE) + realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK); + if (is_vm_hugetlb_page(vma)) return move_hugetlb_page_tables(vma, new_vma, old_addr, new_addr, len); --=20 2.40.1.606.ga4b1b128d6-goog From nobody Sun Feb 8 05:35:11 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 53C12C77B7A for ; Thu, 18 May 2023 02:19:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229905AbjERCTI (ORCPT ); Wed, 17 May 2023 22:19:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56064 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229851AbjERCSs (ORCPT ); Wed, 17 May 2023 22:18:48 -0400 Received: from mail-qt1-x82f.google.com (mail-qt1-x82f.google.com [IPv6:2607:f8b0:4864:20::82f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 63FAA210C for ; Wed, 17 May 2023 19:18:47 -0700 (PDT) Received: by mail-qt1-x82f.google.com with SMTP id d75a77b69052e-3f52009f79dso3739871cf.1 for ; Wed, 17 May 2023 19:18:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1684376326; x=1686968326; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=RjDDJEmMByrSrRAzAnrYD81CTFNgsqIfOqapJ9IGu5M=; b=mQQrGh4h/KNWIK2PoMB6Pztwf3cVCXmBMz0qqgOhBsvYUoYmvpqwqduJIzlAMMC7YK ZrUS/hiBuG72PkbcadbIrnygdqpWVUoSGwOt1fIX6LFaYv2ZtLweuzoryGI5e/lbAEvj QAZwZXY/iYOPxIXmup+iJ05KpzCFPd+H+MV7k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684376326; x=1686968326; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=RjDDJEmMByrSrRAzAnrYD81CTFNgsqIfOqapJ9IGu5M=; b=Q/S1KR0foY6LzmuZjYDbtMUopnF9s0nhgASiCTYbTDub1bxXqkieaK2RucSC7ofZLk 6LFTklhpxd9B2mCUC+PqP9Ey6UQ1m42JIsXBmVCpcZHkcZ1yhZtLzyseDQ7eza3Vfu2u EgKe/bRJ2JcvNhziXnUaK4TM1F8M3alB2bpNGKvyVxgKAN4lM05Lt3Uo69nFEgbX3IGU loPxhgVkMNwuZDsF3Wy1xsDayUAwlGmDHknJl86u5qCK2fxgwJYOSesmwd/Il5uWZT9e gku0AQtgHw1DvU0lyTvGgGIAWOSi1/645fwDeShHWXkQTmQCPRpLZbKDLoWITwy1bsLJ qcIg== X-Gm-Message-State: AC+VfDxpU3uThaMKlrog+pkByD0g80ySWbCkf9LShPFIF5KNgP2mcg72 ZpUUeIymaPg6K5eYIT6Hbi8w/MV4bAudSNFM8aE= X-Google-Smtp-Source: ACHHUZ7onnyA0YRXFWFSrDrQsTcQvuLRzQPOgD7sBT31Y/nwpybDDjLCC9uzwGCwdRjZeUxjOoHbXw== X-Received: by 2002:ac8:588f:0:b0:3f5:2fa4:43bd with SMTP id t15-20020ac8588f000000b003f52fa443bdmr3399132qta.3.1684376325860; Wed, 17 May 2023 19:18:45 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (129.239.188.35.bc.googleusercontent.com. [35.188.239.129]) by smtp.gmail.com with ESMTPSA id j13-20020a05620a000d00b007577ccf566asm85082qki.93.2023.05.17.19.18.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 May 2023 19:18:45 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" Subject: [PATCH RFC 2/4] selftests: mm: Fix failure case when new remap region was not found Date: Thu, 18 May 2023 02:18:23 +0000 Message-ID: <20230518021825.712742-3-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog In-Reply-To: <20230518021825.712742-1-joel@joelfernandes.org> References: <20230518021825.712742-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When a valid remap region could not be found, the source mapping is not cleaned up. Fix the goto statement such that the clean up happens. Signed-off-by: Joel Fernandes (Google) --- tools/testing/selftests/mm/mremap_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selft= ests/mm/mremap_test.c index 5c3773de9f0f..6822d657f589 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -316,7 +316,7 @@ static long long remap_region(struct config c, unsigned= int threshold_mb, if (addr + c.dest_alignment < addr) { ksft_print_msg("Couldn't find a valid region to remap to\n"); ret =3D -1; - goto out; + goto clean_up_src; } addr +=3D c.dest_alignment; } --=20 2.40.1.606.ga4b1b128d6-goog From nobody Sun Feb 8 05:35:11 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65C4BC77B7A for ; Thu, 18 May 2023 02:19:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229577AbjERCTL (ORCPT ); Wed, 17 May 2023 22:19:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56072 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229862AbjERCSs (ORCPT ); Wed, 17 May 2023 22:18:48 -0400 Received: from mail-qk1-x72c.google.com (mail-qk1-x72c.google.com [IPv6:2607:f8b0:4864:20::72c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B3B82213B for ; Wed, 17 May 2023 19:18:47 -0700 (PDT) Received: by mail-qk1-x72c.google.com with SMTP id af79cd13be357-75773a7bd66so169714185a.1 for ; Wed, 17 May 2023 19:18:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1684376326; x=1686968326; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=O+pMaJ78vDhX/WJumeumdh2Ew8rPwZqh+d939UbVmCI=; b=laThT9KmuWwvZ+2Yoy5xsTan07ApYzz/BleFpSz8wK9Si/Q7ltWEJAFVbUqtOZ4D6L TMd2/Y9xWpgxsYsAa9xV49mMbN1y6fwgjT/pKe1dU8Islleu93aNaPSMOLxKyhX/jNrJ 4p5p9XM83q3qupRwXWj+wCh1LxpyNLzARQFWk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684376326; x=1686968326; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=O+pMaJ78vDhX/WJumeumdh2Ew8rPwZqh+d939UbVmCI=; b=K3OeF0vr2oLnSIO/gnKDUC7NTKrph7kaq0jaXLhwwqz8nAYDsjsD1wqfKdX1rPM5mD IYohXIuGKJkjTmBfs86x+MCNOkmO0mI9N3Cj8qbSpr5pyzIlulgewWfobr7N8dRm5+MR jNj8I32lncFBnS0vf5UL6dfb98LHOuYA47TARJj+V0bhdjkwoKd3PphT1g1xFKlwfcEZ EBXE2BsfdRGsY6J9HjUvhgVUjxl7ZyFNnTB9e+rlQeGRjN3dkjiB7+YYjfk3Zy9V74f4 IZE0s8h/0R3uebEF7OBQcanf1cLdlhbu/xt418xN9lA2GB6XYLgomj7WJmwMF8jUvUmx J6JA== X-Gm-Message-State: AC+VfDy4Jtao9CZfeuIwvM6RZ+evQbn63mADOuchhAVfmReJwqdUdNIg MnuABAt7/UNyWh4R4Ep4g35LiIClvjtfMj5epxQ= X-Google-Smtp-Source: ACHHUZ6UnCuj5Nq3VC1ze3Rr3HeldoNEZzJlJJp6jYqyiOJjllcKquWS6RDoPMf5upFCbGWuS1xJyg== X-Received: by 2002:ac8:59cf:0:b0:3f5:315f:5c19 with SMTP id f15-20020ac859cf000000b003f5315f5c19mr3147223qtf.62.1684376326582; Wed, 17 May 2023 19:18:46 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (129.239.188.35.bc.googleusercontent.com. [35.188.239.129]) by smtp.gmail.com with ESMTPSA id j13-20020a05620a000d00b007577ccf566asm85082qki.93.2023.05.17.19.18.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 May 2023 19:18:46 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" Subject: [PATCH RFC 3/4] selftests: mm: Add a test for mutually aligned moves > PMD size Date: Thu, 18 May 2023 02:18:24 +0000 Message-ID: <20230518021825.712742-4-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog In-Reply-To: <20230518021825.712742-1-joel@joelfernandes.org> References: <20230518021825.712742-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This patch adds a test case to check if a PMD-alignment optimization successfully happens. I add support to make sure there is some room before the source mapping, otherwise the optimization to trigger PMD-aligned move will be disabled as the kernel will detect that a mapping before the source exists and such optimization becomes impossible. Signed-off-by: Joel Fernandes (Google) --- tools/testing/selftests/mm/mremap_test.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selft= ests/mm/mremap_test.c index 6822d657f589..6304eb0947a3 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -44,6 +44,7 @@ enum { _1MB =3D 1ULL << 20, _2MB =3D 2ULL << 20, _4MB =3D 4ULL << 20, + _5MB =3D 5ULL << 20, _1GB =3D 1ULL << 30, _2GB =3D 2ULL << 30, PMD =3D _2MB, @@ -235,6 +236,11 @@ static void *get_source_mapping(struct config c) unsigned long long mmap_min_addr; =20 mmap_min_addr =3D get_mmap_min_addr(); + /* + * For some tests, we need to not have any mappings below the + * source mapping. Add some headroom to mmap_min_addr for this. + */ + mmap_min_addr +=3D 10 * _4MB; =20 retry: addr +=3D c.src_alignment; @@ -434,7 +440,7 @@ static int parse_args(int argc, char **argv, unsigned i= nt *threshold_mb, return 0; } =20 -#define MAX_TEST 13 +#define MAX_TEST 14 #define MAX_PERF_TEST 3 int main(int argc, char **argv) { @@ -500,6 +506,10 @@ int main(int argc, char **argv) test_cases[12] =3D MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCC= ESS, "2GB mremap - Source PUD-aligned, Destination PUD-aligned"); =20 + /* Src and Dest addr 1MB aligned. 5MB mremap. */ + test_cases[13] =3D MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SU= CCESS, + "5MB mremap - Source 1MB-aligned, Destination 1MB-aligned"); + perf_test_cases[0] =3D MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAP= PING, EXPECT_SUCCESS, "1GB mremap - Source PTE-aligned, Destination PTE-aligned"); /* --=20 2.40.1.606.ga4b1b128d6-goog From nobody Sun Feb 8 05:35:11 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F159C77B75 for ; Thu, 18 May 2023 02:19:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229815AbjERCTO (ORCPT ); Wed, 17 May 2023 22:19:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229875AbjERCSy (ORCPT ); Wed, 17 May 2023 22:18:54 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A35DE26B1 for ; Wed, 17 May 2023 19:18:48 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id af79cd13be357-7576516c81fso155721985a.1 for ; Wed, 17 May 2023 19:18:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1684376327; x=1686968327; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=tGuemAvtIS/ALPtC/Ke2yJXoSr37KqjSOh21F52Z0b4=; b=XjEWVFgjHhBSgx+JzMuzHzMuMMrg6ZCjBCCAdXf//YzfKBHsPOaTSvveyrxyVc63mB OszLdP5qzb0tPw+Ax1TNz+UB1DuNFET/RCjILS/7u5bCzvBBR1KOj19dWdhgLKcgBzef NYJtJv4KZejE9EsPY58w3IzlHS7ZNhsiLoXuY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684376327; x=1686968327; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=tGuemAvtIS/ALPtC/Ke2yJXoSr37KqjSOh21F52Z0b4=; b=P/BRLGB/geuPaXTI/edfVPIn+Vcvj9Z1nRpc7dNufByLG/3p5LO2Oyr/O0A+EOp3wy mK/9hxMVDmKY26vlV6tubxS/9Wlj2lfkbN8yA5ER+UAT+VVyLB8P5QL1fxy7Wr0W6skq Et/M+iZKCkt1LjeHGxObUv33arn1w+YrBU8xHWkB/Mbl1RrFur1DA4rp4B2YbQwVFOBm jkRSeoN6VjPhhc92zQ3mDYeb4cyCWUiuXnYT7a1HUwS6FOrjrD8D4M+vmuWDV3bsV8j8 ovXzHTAXnCTya/OaQtbr4gmmg/c69qZm0Uhg1zCg4cPZ6DZ3XSBzXD8DmMvZYuxd4TGn dglA== X-Gm-Message-State: AC+VfDzGTDhe1KKDsB6CCu1y7LV9WMniDndlSOGCm4V4U41zf9ggMTl+ mGbOblhhx0wZP82Xd+fNyc6JyXN36mZ0ZxIqdTY= X-Google-Smtp-Source: ACHHUZ4YcOJzn6aoVPNard/VpdQHjhpKxZ/STCMnHfkC5tH5L1a/155XBb4RZDt8EkvRYuJwqaMCWA== X-Received: by 2002:a05:622a:1d0:b0:3ef:366b:5afa with SMTP id t16-20020a05622a01d000b003ef366b5afamr3403956qtw.54.1684376327485; Wed, 17 May 2023 19:18:47 -0700 (PDT) Received: from joelboxx.c.googlers.com.com (129.239.188.35.bc.googleusercontent.com. [35.188.239.129]) by smtp.gmail.com with ESMTPSA id j13-20020a05620a000d00b007577ccf566asm85082qki.93.2023.05.17.19.18.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 May 2023 19:18:46 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Lorenzo Stoakes , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" Subject: [PATCH RFC 4/4] selftests: mm: Add a test for remapping to area immediately after existing mapping Date: Thu, 18 May 2023 02:18:25 +0000 Message-ID: <20230518021825.712742-5-joel@joelfernandes.org> X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog In-Reply-To: <20230518021825.712742-1-joel@joelfernandes.org> References: <20230518021825.712742-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This patch adds support for verifying that we correctly handle the situation where something is already mapped before the destination of the r= emap. Any realignment of destination address and PMD-copy will destroy that existing mapping. In such cases, we need to avoid doing the optimization. To test this, we map an area called the preamble before the remap region. Then we verify after the mremap operation that this region did not = get corrupted. Putting some prints in the kernel, I verified that we optimize correctly in different situations: Optimize when there is alignment and no previous mapping (this is tested by previous patch). check_addr_in_prev(old_vma->vm_start=3D2900000, old_addr=3D2900000, mask=3D= -2097152): 0 check_addr_in_prev(new_vma->vm_start=3D2f00000, new_addr=3D2f00000, mask=3D= -2097152): 0 =3D=3D=3D Starting move_page_tables =3D=3D=3D Doing PUD move for 2800000 -> 2e00000 of extent=3D200000 <-- Optimization Doing PUD move for 2a00000 -> 3000000 of extent=3D200000 Doing PUD move for 2c00000 -> 3200000 of extent=3D200000 Don't optimize when there is alignment but there is previous mapping (this is tested by this patch). Notice that check_addr_in_prev() returns 1 for the destination mapping as we detected there is something there. check_addr_in_prev(old_vma->vm_start=3D2900000, old_addr=3D2900000, mask=3D= -2097152): 0 check_addr_in_prev(new_vma->vm_start=3D5700000, new_addr=3D5700000, mask=3D= -2097152): 1 =3D=3D=3D Starting move_page_tables =3D=3D=3D Doing move_ptes for 2900000 -> 5700000 of extent=3D100000 <-- Unoptimized Doing PUD move for 2a00000 -> 5800000 of extent=3D200000 Doing PUD move for 2c00000 -> 5a00000 of extent=3D200000 Signed-off-by: Joel Fernandes (Google) --- tools/testing/selftests/mm/mremap_test.c | 57 +++++++++++++++++++++--- 1 file changed, 52 insertions(+), 5 deletions(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selft= ests/mm/mremap_test.c index 6304eb0947a3..d7366074e2a8 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -29,6 +29,7 @@ struct config { unsigned long long dest_alignment; unsigned long long region_size; int overlapping; + int dest_preamble_size; }; =20 struct test { @@ -283,7 +284,7 @@ static void *get_source_mapping(struct config c) static long long remap_region(struct config c, unsigned int threshold_mb, char pattern_seed) { - void *addr, *src_addr, *dest_addr; + void *addr, *src_addr, *dest_addr, *dest_preamble_addr; unsigned long long i; struct timespec t_start =3D {0, 0}, t_end =3D {0, 0}; long long start_ns, end_ns, align_mask, ret, offset; @@ -300,7 +301,7 @@ static long long remap_region(struct config c, unsigned= int threshold_mb, goto out; } =20 - /* Set byte pattern */ + /* Set byte pattern for source block. */ srand(pattern_seed); for (i =3D 0; i < threshold; i++) memset((char *) src_addr + i, (char) rand(), 1); @@ -312,6 +313,9 @@ static long long remap_region(struct config c, unsigned= int threshold_mb, addr =3D (void *) (((unsigned long long) src_addr + c.region_size + offset) & align_mask); =20 + /* Remap after the destination block preamble. */ + addr +=3D c.dest_preamble_size; + /* See comment in get_source_mapping() */ if (!((unsigned long long) addr & c.dest_alignment)) addr =3D (void *) ((unsigned long long) addr | c.dest_alignment); @@ -327,6 +331,24 @@ static long long remap_region(struct config c, unsigne= d int threshold_mb, addr +=3D c.dest_alignment; } =20 + if (c.dest_preamble_size) { + dest_preamble_addr =3D mmap((void *) addr - c.dest_preamble_size, c.dest= _preamble_size, + PROT_READ | PROT_WRITE, + MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED, + -1, 0); + if (dest_preamble_addr =3D=3D MAP_FAILED) { + ksft_print_msg("Failed to map dest preamble region: %s\n", + strerror(errno)); + ret =3D -1; + goto clean_up_src; + } + + /* Set byte pattern for the dest preamble block. */ + srand(pattern_seed); + for (i =3D 0; i < c.dest_preamble_size; i++) + memset((char *) dest_preamble_addr + i, (char) rand(), 1); + } + clock_gettime(CLOCK_MONOTONIC, &t_start); dest_addr =3D mremap(src_addr, c.region_size, c.region_size, MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr); @@ -335,7 +357,7 @@ static long long remap_region(struct config c, unsigned= int threshold_mb, if (dest_addr =3D=3D MAP_FAILED) { ksft_print_msg("mremap failed: %s\n", strerror(errno)); ret =3D -1; - goto clean_up_src; + goto clean_up_dest_preamble; } =20 /* Verify byte pattern after remapping */ @@ -353,6 +375,23 @@ static long long remap_region(struct config c, unsigne= d int threshold_mb, } } =20 + /* Verify the dest preamble byte pattern after remapping */ + if (c.dest_preamble_size) { + srand(pattern_seed); + for (i =3D 0; i < c.dest_preamble_size; i++) { + char c =3D (char) rand(); + + if (((char *) dest_preamble_addr)[i] !=3D c) { + ksft_print_msg("Preamble data after remap doesn't match at offset %d\n= ", + i); + ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff, + ((char *) dest_preamble_addr)[i] & 0xff); + ret =3D -1; + goto clean_up_dest; + } + } + } + start_ns =3D t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec; end_ns =3D t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec; ret =3D end_ns - start_ns; @@ -365,6 +404,9 @@ static long long remap_region(struct config c, unsigned= int threshold_mb, */ clean_up_dest: munmap(dest_addr, c.region_size); +clean_up_dest_preamble: + if (c.dest_preamble_size && dest_preamble_addr) + munmap(dest_preamble_addr, c.dest_preamble_size); clean_up_src: munmap(src_addr, c.region_size); out: @@ -440,7 +482,7 @@ static int parse_args(int argc, char **argv, unsigned i= nt *threshold_mb, return 0; } =20 -#define MAX_TEST 14 +#define MAX_TEST 15 #define MAX_PERF_TEST 3 int main(int argc, char **argv) { @@ -449,7 +491,7 @@ int main(int argc, char **argv) unsigned int threshold_mb =3D VALIDATION_DEFAULT_THRESHOLD; unsigned int pattern_seed; int num_expand_tests =3D 2; - struct test test_cases[MAX_TEST]; + struct test test_cases[MAX_TEST] =3D {}; struct test perf_test_cases[MAX_PERF_TEST]; int page_size; time_t t; @@ -510,6 +552,11 @@ int main(int argc, char **argv) test_cases[13] =3D MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SU= CCESS, "5MB mremap - Source 1MB-aligned, Destination 1MB-aligned"); =20 + /* Src and Dest addr 1MB aligned. 5MB mremap. */ + test_cases[14] =3D MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SU= CCESS, + "5MB mremap - Source 1MB-aligned, Dest 1MB-aligned with 40MB Preambl= e"); + test_cases[14].config.dest_preamble_size =3D 10 * _4MB; + perf_test_cases[0] =3D MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAP= PING, EXPECT_SUCCESS, "1GB mremap - Source PTE-aligned, Destination PTE-aligned"); /* --=20 2.40.1.606.ga4b1b128d6-goog