From patchwork Sun Sep 3 15:13:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 719919 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 40E68CA0FE3 for ; Sun, 3 Sep 2023 15:13:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243373AbjICPNm (ORCPT ); Sun, 3 Sep 2023 11:13:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47958 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243295AbjICPNl (ORCPT ); Sun, 3 Sep 2023 11:13:41 -0400 Received: from mail-io1-xd2b.google.com (mail-io1-xd2b.google.com [IPv6:2607:f8b0:4864:20::d2b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2EDB2118 for ; Sun, 3 Sep 2023 08:13:38 -0700 (PDT) Received: by mail-io1-xd2b.google.com with SMTP id ca18e2360f4ac-795547f055fso33808039f.0 for ; Sun, 03 Sep 2023 08:13:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1693754017; x=1694358817; darn=vger.kernel.org; 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=L4plAmoxt0TIZz59K3TwGGgNGB354bzgqE5y3am6jPM=; b=tbXIpgfSOxUppfhpAF7YQgdPvus3o7YClNsvbLqZx/mQ8FFCPpJy04oAAYHKT1RV4v 28vSItNSLvFZRcXsXoXE4T5+du1AgR/xS6fVSUa8ssmDzUgDmY2NHWbXnjgmqlYnTCLK S1smp78E/XNZEB90mQ/TTiAWlphEjTRNSnCi0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693754017; x=1694358817; 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=L4plAmoxt0TIZz59K3TwGGgNGB354bzgqE5y3am6jPM=; b=Jc0x55vAKJR2BMwnOJv6geILW1PtTH1sfxBYDJE4omfHvyZlmRJ6QLyOktCz5Et0+S R4TOdfLy5YO4gJj+UMtjaJSz0XvqEL+XoWwuNE4G44baBYioPTCt9hgXyqeG6v5xeUGv TQSI23oXskR9c+rEzApT/9dmcKKUiuR+LYyKZcIKWEIYpI8x9uzfObPWKcEjGst6yBko tlk+FWqtXBGaSq0E7v/JcTGxzGvFQZ0IiL5L+rCsHhVjHFt19++6mKBb+RdMFoQv7orD /MEgZDrc/j9niq+raQXPOTbxiqglajjW5D7lwrjR2N8oWTbFwZPOADRHEx+3+RN1ZGuA T17w== X-Gm-Message-State: AOJu0Yx88kc1xNufiXiA3CxMfQsfk12npA8r4fsIov/CKWoA3CrZl9q3 r4T0Gr2u7KjDzUcp9W994o+Q6g== X-Google-Smtp-Source: AGHT+IHJGQrTQCQWJADO7oGCiqQCRPPFaXSY0O8+5g3/GiBjHqRcTCt3H4l78vIVACIFoG7YASx0Jw== X-Received: by 2002:a6b:7f46:0:b0:791:2db5:c779 with SMTP id m6-20020a6b7f46000000b007912db5c779mr11231804ioq.10.1693754017569; Sun, 03 Sep 2023 08:13:37 -0700 (PDT) Received: from joelboxx5.corp.google.com (156.190.123.34.bc.googleusercontent.com. [34.123.190.156]) by smtp.gmail.com with ESMTPSA id f5-20020a6b5105000000b007835a305f61sm2605897iob.36.2023.09.03.08.13.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Sep 2023 08:13:36 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Lorenzo Stoakes , Linus Torvalds , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan , Kalesh Singh , Lokesh Gidra Subject: [PATCH v6 1/7] mm/mremap: Optimize the start addresses in move_page_tables() Date: Sun, 3 Sep 2023 15:13:22 +0000 Message-ID: <20230903151328.2981432-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog In-Reply-To: <20230903151328.2981432-1-joel@joelfernandes.org> References: <20230903151328.2981432-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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. 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. d. We need to be careful about mremap of ranges within the VMA itself. For this purpose, I added checks to determine if the address after alignment falls within its VMA itself. [1] https://lore.kernel.org/all/ZB2GTBD%2FLWTrkOiO@dhcp22.suse.cz/ [2] https://lore.kernel.org/all/CAHk-=whd7msp8reJPfeGNyt0LiySMT0egExx3TVZSX3Ok6X=9g@mail.gmail.com/ Reviewed-by: Lorenzo Stoakes Suggested-by: Linus Torvalds Signed-off-by: Joel Fernandes (Google) --- mm/mremap.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index 11e06e4ab33b..1011326b7b80 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -489,6 +489,53 @@ static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, return moved; } +/* + * 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 can_align_down(struct vm_area_struct *vma, unsigned long addr_to_align, + unsigned long mask) +{ + unsigned long addr_masked = addr_to_align & mask; + + /* + * If @addr_to_align of either source or destination is not the beginning + * of the corresponding VMA, we can't align down or we will destroy part + * of the current mapping. + */ + if (vma->vm_start != addr_to_align) + return false; + + /* + * Make sure the realignment doesn't cause the address to fall on an + * existing mapping. + */ + return find_vma_intersection(vma->vm_mm, addr_masked, vma->vm_start) == NULL; +} + +/* Opportunistically realign to specified boundary for faster copy. */ +static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma, + unsigned long *new_addr, struct vm_area_struct *new_vma, + unsigned long mask) +{ + /* Skip if the addresses are already aligned. */ + if ((*old_addr & ~mask) == 0) + return; + + /* Only realign if the new and old addresses are mutually aligned. */ + if ((*old_addr & ~mask) != (*new_addr & ~mask)) + return; + + /* Ensure realignment doesn't cause overlap with existing mappings. */ + if (!can_align_down(old_vma, *old_addr, mask) || + !can_align_down(new_vma, *new_addr, mask)) + return; + + *old_addr = *old_addr & mask; + *new_addr = *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, @@ -508,6 +555,14 @@ unsigned long move_page_tables(struct vm_area_struct *vma, return move_hugetlb_page_tables(vma, new_vma, old_addr, new_addr, len); + /* + * If possible, realign addresses to PMD boundary for faster copy. + * Only realign if the mremap copying hits a PMD boundary. + */ + if ((vma != new_vma) + && (len >= PMD_SIZE - (old_addr & ~PMD_MASK))) + try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK); + flush_cache_range(vma, old_addr, old_end); mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm, old_addr, old_end); @@ -577,6 +632,13 @@ unsigned long move_page_tables(struct vm_area_struct *vma, mmu_notifier_invalidate_range_end(&range); + /* + * Prevent negative return values when {old,new}_addr was realigned + * but we broke out of the above loop for the first PMD itself. + */ + if (len + old_addr < old_end) + return 0; + return len + old_addr - old_end; /* how much done */ } From patchwork Sun Sep 3 15:13:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 719918 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 69DF0CA0FE3 for ; Sun, 3 Sep 2023 15:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243412AbjICPNp (ORCPT ); Sun, 3 Sep 2023 11:13:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53722 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243389AbjICPNm (ORCPT ); Sun, 3 Sep 2023 11:13:42 -0400 Received: from mail-io1-xd32.google.com (mail-io1-xd32.google.com [IPv6:2607:f8b0:4864:20::d32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15855115 for ; Sun, 3 Sep 2023 08:13:39 -0700 (PDT) Received: by mail-io1-xd32.google.com with SMTP id ca18e2360f4ac-792707f78b5so37988539f.1 for ; Sun, 03 Sep 2023 08:13:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1693754018; x=1694358818; darn=vger.kernel.org; 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=Oa7N2sPH/lilO/UwWqLMR+jDCHXNj+j722SD4+8DAS8=; b=p3ecb/r3Oez3FeX0zxpD3f9Ziln558UEzDLpuqh8HNXSknzOxmT4SPodW6rM8VjH8D Azrhc/vJThEJlKmycWClmEDvDZx4Giojf1un9nRL8S2WIhPxg8+KOoamMha3GHXFz0Wo +qIziE2JNDpIejHJ5haC6paenH8shfjHOMx2c= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693754018; x=1694358818; 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=Oa7N2sPH/lilO/UwWqLMR+jDCHXNj+j722SD4+8DAS8=; b=Jatum3/pSGH7X4HMoeI4vrBNgMolv2rUrBkfu8Szx+zeZCTnw4n0CjPb08pbyooUgK 4F4x2b39zSwzrAVH/ZQKvZfrTSZfBciF10Qyw5fC13dTHM3suZo34ao0idXWCM7HOSzE CNx2SCMyTch6jE4rKkp4JqDcH674AffIu8rdMaYdt0bw3EyWpAP9np5RoJuxzFuHwKNq UZuVqP7ZmUE50XmiA4SV5rl6iD+X+4Q71CnVrTFgTBlkPE5J6yZWoKXh73ro3xRFkmly 68Lez0JqI6eH5DJaPKRu8bdu1jENrklikBHyE3pYWjyz36j5KFu5MuRSI9UG0qyHavwp qeww== X-Gm-Message-State: AOJu0YxVBvBsuDzwbtLTGdiSCnMzRemfCBeuBxhGdc2cFP/Lz5a9F6NJ x2ucHkO4iq46ZH94M+dvOdtD8w== X-Google-Smtp-Source: AGHT+IGTBN7+8BUOuxu3HzD4jDZmr/y5lg4NupMcQKdCe0g07b+paLWsn6FtLb2h4fhMmD0ruozikg== X-Received: by 2002:a05:6602:210b:b0:787:169a:927 with SMTP id x11-20020a056602210b00b00787169a0927mr8408605iox.20.1693754018437; Sun, 03 Sep 2023 08:13:38 -0700 (PDT) Received: from joelboxx5.corp.google.com (156.190.123.34.bc.googleusercontent.com. [34.123.190.156]) by smtp.gmail.com with ESMTPSA id f5-20020a6b5105000000b007835a305f61sm2605897iob.36.2023.09.03.08.13.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Sep 2023 08:13:37 -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" , Suren Baghdasaryan , Kalesh Singh , Lokesh Gidra Subject: [PATCH v6 2/7] mm/mremap: Allow moves within the same VMA for stack moves Date: Sun, 3 Sep 2023 15:13:23 +0000 Message-ID: <20230903151328.2981432-3-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog In-Reply-To: <20230903151328.2981432-1-joel@joelfernandes.org> References: <20230903151328.2981432-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org For the stack move happening in shift_arg_pages(), the move is happening within the same VMA which spans the old and new ranges. In case the aligned address happens to fall within that VMA, allow such moves and don't abort the mremap alignment optimization. In the regular non-stack mremap case, we cannot allow any such moves as will end up destroying some part of the mapping (either the source of the move, or part of the existing mapping). So just avoid it for stack moves. Signed-off-by: Joel Fernandes (Google) Reviewed-by: Lorenzo Stoakes Acked-by: Michal Hocko --- fs/exec.c | 2 +- include/linux/mm.h | 2 +- mm/mremap.c | 33 +++++++++++++++++++-------------- 3 files changed, 21 insertions(+), 16 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 1a827d55ba94..244925307958 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -712,7 +712,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) * process cleanup to remove whatever mess we made. */ if (length != move_page_tables(vma, old_start, - vma, new_start, length, false)) + vma, new_start, length, false, true)) return -ENOMEM; lru_add_drain(); diff --git a/include/linux/mm.h b/include/linux/mm.h index 406ab9ea818f..e635d1fc73b6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2458,7 +2458,7 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); extern 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, - bool need_rmap_locks); + bool need_rmap_locks, bool for_stack); /* * Flags used by change_protection(). For now we make it a bitmap so diff --git a/mm/mremap.c b/mm/mremap.c index 1011326b7b80..2b51f8b7cad8 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -490,12 +490,13 @@ static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma, } /* - * 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. + * A helper to check if aligning down is OK. The aligned address should fall + * on *no mapping*. For the stack moving down, that's a special move within + * the VMA that is created to span the source and destination of the move, + * so we make an exception for it. */ static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_align, - unsigned long mask) + unsigned long mask, bool for_stack) { unsigned long addr_masked = addr_to_align & mask; @@ -504,9 +505,13 @@ static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_ali * of the corresponding VMA, we can't align down or we will destroy part * of the current mapping. */ - if (vma->vm_start != addr_to_align) + if (!for_stack && vma->vm_start != addr_to_align) return false; + /* In the stack case we explicitly permit in-VMA alignment. */ + if (for_stack && addr_masked >= vma->vm_start) + return true; + /* * Make sure the realignment doesn't cause the address to fall on an * existing mapping. @@ -517,7 +522,7 @@ static bool can_align_down(struct vm_area_struct *vma, unsigned long addr_to_ali /* Opportunistically realign to specified boundary for faster copy. */ static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old_vma, unsigned long *new_addr, struct vm_area_struct *new_vma, - unsigned long mask) + unsigned long mask, bool for_stack) { /* Skip if the addresses are already aligned. */ if ((*old_addr & ~mask) == 0) @@ -528,8 +533,8 @@ static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old return; /* Ensure realignment doesn't cause overlap with existing mappings. */ - if (!can_align_down(old_vma, *old_addr, mask) || - !can_align_down(new_vma, *new_addr, mask)) + if (!can_align_down(old_vma, *old_addr, mask, for_stack) || + !can_align_down(new_vma, *new_addr, mask, for_stack)) return; *old_addr = *old_addr & mask; @@ -539,7 +544,7 @@ static void try_realign_addr(unsigned long *old_addr, struct vm_area_struct *old 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, - bool need_rmap_locks) + bool need_rmap_locks, bool for_stack) { unsigned long extent, old_end; struct mmu_notifier_range range; @@ -559,9 +564,9 @@ unsigned long move_page_tables(struct vm_area_struct *vma, * If possible, realign addresses to PMD boundary for faster copy. * Only realign if the mremap copying hits a PMD boundary. */ - if ((vma != new_vma) - && (len >= PMD_SIZE - (old_addr & ~PMD_MASK))) - try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK); + if (len >= PMD_SIZE - (old_addr & ~PMD_MASK)) + try_realign_addr(&old_addr, vma, &new_addr, new_vma, PMD_MASK, + for_stack); flush_cache_range(vma, old_addr, old_end); mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm, @@ -708,7 +713,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, } moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, - need_rmap_locks); + need_rmap_locks, false); if (moved_len < old_len) { err = -ENOMEM; } else if (vma->vm_ops && vma->vm_ops->mremap) { @@ -722,7 +727,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, * and then proceed to unmap new area instead of old. */ move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, - true); + true, false); vma = new_vma; old_len = new_len; old_addr = new_addr; From patchwork Sun Sep 3 15:13:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 719917 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 DAB4BCA0FF3 for ; Sun, 3 Sep 2023 15:13:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243295AbjICPNu (ORCPT ); Sun, 3 Sep 2023 11:13:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53788 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243483AbjICPNp (ORCPT ); Sun, 3 Sep 2023 11:13:45 -0400 Received: from mail-io1-xd32.google.com (mail-io1-xd32.google.com [IPv6:2607:f8b0:4864:20::d32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B59A7AF for ; Sun, 3 Sep 2023 08:13:41 -0700 (PDT) Received: by mail-io1-xd32.google.com with SMTP id ca18e2360f4ac-792965813e7so30064439f.2 for ; Sun, 03 Sep 2023 08:13:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1693754021; x=1694358821; darn=vger.kernel.org; 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=+BMtnhYdeu/zB56jX4tl+3iW5OG7Lep/G1Bzlyk4Cto=; b=t/vtfEzYtLVv1yf2Lo7ALU4J2usC6H/HyqzAIFvreHvc91Lg1/S4u1MpnMjtdvH+Sf BPZtO3oPSPNGkTCRM6aRRFT+T9aSKnESqRIyUBsJ54BcD8tWU8IKBVANgYP1jugU2RK6 XCpkyOR9c0LDmFaG7jgf5VzEkMvoBbH6mSORI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693754021; x=1694358821; 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=+BMtnhYdeu/zB56jX4tl+3iW5OG7Lep/G1Bzlyk4Cto=; b=dD51I7WvmmocpNBAHwq4SA8fuW77wc4XQyws7VtSGZpY6jip4UD/KHh/lLqoV5rSNf ZqdYvdbdDnmynZmyXGVjkMFkzMzhsj3O3pwNFz/q/5NAKUcwyHq/W4u/QoviSMLjeqMm x/McZRHlc+DCweNGjoasPJjkoTCp1HalAfrMqYqr3CkjpWldlmUJ0WaSIs576YfeGQTu A/g3Qi5qn4U7dxdFGKSOr1mOT7xEitY3maQ490eezGzpB5Gm5kHPTtii7RrgVILJZvAI TCQDeIXl2GNmxvwvDhhK1pX1Z0ofDtBJZL0hwbAzdK7zc67UA7podPZ26j9Nb64tlO8f k49A== X-Gm-Message-State: AOJu0YwAEzBZ22l1aD1UBTTyCI62wcHFVqy0gq91gcNV6QkY1e1HZdET 3sz1bE5qF/HcURZJT0PVlWGnyQ== X-Google-Smtp-Source: AGHT+IGoiNLSWXDDcRwa+CUKmoRj1KyKVnC5w9SpA0dWyRbwniu1q3CeYE3pp5OaUl5HGdBBsO8atw== X-Received: by 2002:a6b:f104:0:b0:795:1a7c:486f with SMTP id e4-20020a6bf104000000b007951a7c486fmr8841640iog.14.1693754021116; Sun, 03 Sep 2023 08:13:41 -0700 (PDT) Received: from joelboxx5.corp.google.com (156.190.123.34.bc.googleusercontent.com. [34.123.190.156]) by smtp.gmail.com with ESMTPSA id f5-20020a6b5105000000b007835a305f61sm2605897iob.36.2023.09.03.08.13.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Sep 2023 08:13:40 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: "Joel Fernandes (Google)" , Lorenzo Stoakes , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan , Kalesh Singh , Lokesh Gidra Subject: [PATCH v6 5/7] selftests: mm: Add a test for remapping to area immediately after existing mapping Date: Sun, 3 Sep 2023 15:13:26 +0000 Message-ID: <20230903151328.2981432-6-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog In-Reply-To: <20230903151328.2981432-1-joel@joelfernandes.org> References: <20230903151328.2981432-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org This patch adds support for verifying that we correctly handle the situation where something is already mapped before the destination of the remap. 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). can_align_down(old_vma->vm_start=2900000, old_addr=2900000, mask=-2097152): 0 can_align_down(new_vma->vm_start=2f00000, new_addr=2f00000, mask=-2097152): 0 === Starting move_page_tables === Doing PUD move for 2800000 -> 2e00000 of extent=200000 <-- Optimization Doing PUD move for 2a00000 -> 3000000 of extent=200000 Doing PUD move for 2c00000 -> 3200000 of extent=200000 Don't optimize when there is alignment but there is previous mapping (this is tested by this patch). Notice that can_align_down() returns 1 for the destination mapping as we detected there is something there. can_align_down(old_vma->vm_start=2900000, old_addr=2900000, mask=-2097152): 0 can_align_down(new_vma->vm_start=5700000, new_addr=5700000, mask=-2097152): 1 === Starting move_page_tables === Doing move_ptes for 2900000 -> 5700000 of extent=100000 <-- Unoptimized Doing PUD move for 2a00000 -> 5800000 of extent=200000 Doing PUD move for 2c00000 -> 5a00000 of extent=200000 Reviewed-by: Lorenzo Stoakes 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/selftests/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; }; 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 = {0, 0}, t_end = {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; } - /* Set byte pattern */ + /* Set byte pattern for source block. */ srand(pattern_seed); for (i = 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 = (void *) (((unsigned long long) src_addr + c.region_size + offset) & align_mask); + /* Remap after the destination block preamble. */ + addr += c.dest_preamble_size; + /* See comment in get_source_mapping() */ if (!((unsigned long long) addr & c.dest_alignment)) addr = (void *) ((unsigned long long) addr | c.dest_alignment); @@ -327,6 +331,24 @@ static long long remap_region(struct config c, unsigned int threshold_mb, addr += c.dest_alignment; } + if (c.dest_preamble_size) { + dest_preamble_addr = 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 == MAP_FAILED) { + ksft_print_msg("Failed to map dest preamble region: %s\n", + strerror(errno)); + ret = -1; + goto clean_up_src; + } + + /* Set byte pattern for the dest preamble block. */ + srand(pattern_seed); + for (i = 0; i < c.dest_preamble_size; i++) + memset((char *) dest_preamble_addr + i, (char) rand(), 1); + } + clock_gettime(CLOCK_MONOTONIC, &t_start); dest_addr = 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 == MAP_FAILED) { ksft_print_msg("mremap failed: %s\n", strerror(errno)); ret = -1; - goto clean_up_src; + goto clean_up_dest_preamble; } /* Verify byte pattern after remapping */ @@ -353,6 +375,23 @@ static long long remap_region(struct config c, unsigned int threshold_mb, } } + /* Verify the dest preamble byte pattern after remapping */ + if (c.dest_preamble_size) { + srand(pattern_seed); + for (i = 0; i < c.dest_preamble_size; i++) { + char c = (char) rand(); + + if (((char *) dest_preamble_addr)[i] != 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 = -1; + goto clean_up_dest; + } + } + } + start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec; end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec; ret = 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 int *threshold_mb, return 0; } -#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 = VALIDATION_DEFAULT_THRESHOLD; unsigned int pattern_seed; int num_expand_tests = 2; - struct test test_cases[MAX_TEST]; + struct test test_cases[MAX_TEST] = {}; 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] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS, "5MB mremap - Source 1MB-aligned, Destination 1MB-aligned"); + /* Src and Dest addr 1MB aligned. 5MB mremap. */ + test_cases[14] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS, + "5MB mremap - Source 1MB-aligned, Dest 1MB-aligned with 40MB Preamble"); + test_cases[14].config.dest_preamble_size = 10 * _4MB; + perf_test_cases[0] = MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS, "1GB mremap - Source PTE-aligned, Destination PTE-aligned"); /* From patchwork Sun Sep 3 15:13:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Joel Fernandes \(Google\)" X-Patchwork-Id: 719916 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 627DFC83F2C for ; Sun, 3 Sep 2023 15:13:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244223AbjICPNx (ORCPT ); Sun, 3 Sep 2023 11:13:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53848 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243793AbjICPNt (ORCPT ); Sun, 3 Sep 2023 11:13:49 -0400 Received: from mail-io1-xd30.google.com (mail-io1-xd30.google.com [IPv6:2607:f8b0:4864:20::d30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9936612A for ; Sun, 3 Sep 2023 08:13:43 -0700 (PDT) Received: by mail-io1-xd30.google.com with SMTP id ca18e2360f4ac-79564282cb1so21313239f.2 for ; Sun, 03 Sep 2023 08:13:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; t=1693754023; x=1694358823; darn=vger.kernel.org; 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=f+nqtAseasZFOdOpIwYvU1wfrPMXCZ3Zt4BE+IzJOeI=; b=icCM7tAzofuObhoJQPpsMpaO+grSsCguGAmim704GqP8i0u1ttjtGUGUoHa3E5vRjs zKxkWRouRndPglhy6x+rPOwjcFPdDCi93iOcjGd+LXmjzx2cItmRTPTG83TYiYP7RiAU fnxCDKydFoOsyu+ocnnMmvLl1vFOjDaUJGR6w= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693754023; x=1694358823; 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=f+nqtAseasZFOdOpIwYvU1wfrPMXCZ3Zt4BE+IzJOeI=; b=Xm80vcrB1EF1cqy912Pt2TTkmiGaGo3jcg9hIcx1SrDSZ1pO149n6AwbgsAgND5yAf jbtDiRquYgPwamlh3jTL2+VUsvggTTK4UVsbTJFe4iS3cUAmyG2KuuEaSPxHfY4wdGLS 1kEdohc2IEPEJFJY0rpbv5X0ZtFDX3DQXFd138RwQx5LVesxaTpJuz2gU4LJxiy96/WC qnec6k5XWUjIasPCBvE3AzqJG4QeUf5JoGv/e1/kjFuWh1zh4N+nfdcGIUdMoF55ckyQ TVFPdRMTwfkrk+cnoZm0FkwQuYkt/7+2ej8cFv2tae+f35o+6BxnCkkKA1wjJtJIr5XC TwCw== X-Gm-Message-State: AOJu0Yze8Dom+z0NBTW3jNg0q7XTYaOnqoBhEL6jKpBzYO3mO2h/cEJU T9c7bvUPxlOx3/xMOWm/Kb6tlg== X-Google-Smtp-Source: AGHT+IG0ubtl3WQP2iLAfgo/8U3Gp+Qcadj9ljmVKqqAyOzu0TCZj645xHn8dTLLCtLKiiIphITokw== X-Received: by 2002:a6b:ec16:0:b0:792:82f8:6f90 with SMTP id c22-20020a6bec16000000b0079282f86f90mr8856879ioh.16.1693754022914; Sun, 03 Sep 2023 08:13:42 -0700 (PDT) Received: from joelboxx5.corp.google.com (156.190.123.34.bc.googleusercontent.com. [34.123.190.156]) by smtp.gmail.com with ESMTPSA id f5-20020a6b5105000000b007835a305f61sm2605897iob.36.2023.09.03.08.13.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Sep 2023 08:13:42 -0700 (PDT) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org Cc: Joel Fernandes , Lorenzo Stoakes , linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Shuah Khan , Vlastimil Babka , Michal Hocko , Linus Torvalds , Kirill A Shutemov , "Liam R. Howlett" , "Paul E. McKenney" , Suren Baghdasaryan , Kalesh Singh , Lokesh Gidra Subject: [PATCH v6 7/7] selftests: mm: Add a test for moving from an offset from start of mapping Date: Sun, 3 Sep 2023 15:13:28 +0000 Message-ID: <20230903151328.2981432-8-joel@joelfernandes.org> X-Mailer: git-send-email 2.42.0.283.g2d96d420d3-goog In-Reply-To: <20230903151328.2981432-1-joel@joelfernandes.org> References: <20230903151328.2981432-1-joel@joelfernandes.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org From: Joel Fernandes It is possible that the aligned address falls on no existing mapping, however that does not mean that we can just align it down to that. This test verifies that the "vma->vm_start != addr_to_align" check in can_align_down() prevents disastrous results if aligning down when source and dest are mutually aligned within a PMD but the source/dest addresses requested are not at the beginning of the respective mapping containing these addresses. Reviewed-by: Lorenzo Stoakes Signed-off-by: Joel Fernandes (Google) --- tools/testing/selftests/mm/mremap_test.c | 189 ++++++++++++++++------- 1 file changed, 134 insertions(+), 55 deletions(-) diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c index 12a095457f4c..1f836e670a37 100644 --- a/tools/testing/selftests/mm/mremap_test.c +++ b/tools/testing/selftests/mm/mremap_test.c @@ -24,6 +24,7 @@ #define MIN(X, Y) ((X) < (Y) ? (X) : (Y)) #define SIZE_MB(m) ((size_t)m * (1024 * 1024)) +#define SIZE_KB(k) ((size_t)k * 1024) struct config { unsigned long long src_alignment; @@ -148,6 +149,60 @@ static bool is_range_mapped(FILE *maps_fp, void *start, void *end) return success; } +/* + * Returns the start address of the mapping on success, else returns + * NULL on failure. + */ +static void *get_source_mapping(struct config c) +{ + unsigned long long addr = 0ULL; + void *src_addr = NULL; + unsigned long long mmap_min_addr; + + mmap_min_addr = 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 += 10 * _4MB; + +retry: + addr += c.src_alignment; + if (addr < mmap_min_addr) + goto retry; + + src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE, + MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED, + -1, 0); + if (src_addr == MAP_FAILED) { + if (errno == EPERM || errno == EEXIST) + goto retry; + goto error; + } + /* + * Check that the address is aligned to the specified alignment. + * Addresses which have alignments that are multiples of that + * specified are not considered valid. For instance, 1GB address is + * 2MB-aligned, however it will not be considered valid for a + * requested alignment of 2MB. This is done to reduce coincidental + * alignment in the tests. + */ + if (((unsigned long long) src_addr & (c.src_alignment - 1)) || + !((unsigned long long) src_addr & c.src_alignment)) { + munmap(src_addr, c.region_size); + goto retry; + } + + if (!src_addr) + goto error; + + return src_addr; +error: + ksft_print_msg("Failed to map source region: %s\n", + strerror(errno)); + return NULL; +} + /* * This test validates that merge is called when expanding a mapping. * Mapping containing three pages is created, middle page is unmapped @@ -300,60 +355,6 @@ static void mremap_move_within_range(char pattern_seed) ksft_test_result_fail("%s\n", test_name); } -/* - * Returns the start address of the mapping on success, else returns - * NULL on failure. - */ -static void *get_source_mapping(struct config c) -{ - unsigned long long addr = 0ULL; - void *src_addr = NULL; - unsigned long long mmap_min_addr; - - mmap_min_addr = 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 += 10 * _4MB; - -retry: - addr += c.src_alignment; - if (addr < mmap_min_addr) - goto retry; - - src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE, - MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED, - -1, 0); - if (src_addr == MAP_FAILED) { - if (errno == EPERM || errno == EEXIST) - goto retry; - goto error; - } - /* - * Check that the address is aligned to the specified alignment. - * Addresses which have alignments that are multiples of that - * specified are not considered valid. For instance, 1GB address is - * 2MB-aligned, however it will not be considered valid for a - * requested alignment of 2MB. This is done to reduce coincidental - * alignment in the tests. - */ - if (((unsigned long long) src_addr & (c.src_alignment - 1)) || - !((unsigned long long) src_addr & c.src_alignment)) { - munmap(src_addr, c.region_size); - goto retry; - } - - if (!src_addr) - goto error; - - return src_addr; -error: - ksft_print_msg("Failed to map source region: %s\n", - strerror(errno)); - return NULL; -} - /* Returns the time taken for the remap on success else returns -1. */ static long long remap_region(struct config c, unsigned int threshold_mb, char pattern_seed) @@ -487,6 +488,83 @@ static long long remap_region(struct config c, unsigned int threshold_mb, return ret; } +/* + * Verify that an mremap aligning down does not destroy + * the beginning of the mapping just because the aligned + * down address landed on a mapping that maybe does not exist. + */ +static void mremap_move_1mb_from_start(char pattern_seed) +{ + char *test_name = "mremap move 1mb from start at 1MB+256KB aligned src"; + void *src = NULL, *dest = NULL; + int i, success = 1; + + /* Config to reuse get_source_mapping() to do an aligned mmap. */ + struct config c = { + .src_alignment = SIZE_MB(1) + SIZE_KB(256), + .region_size = SIZE_MB(6) + }; + + src = get_source_mapping(c); + if (!src) { + success = 0; + goto out; + } + + c.src_alignment = SIZE_MB(1) + SIZE_KB(256); + dest = get_source_mapping(c); + if (!dest) { + success = 0; + goto out; + } + + /* Set byte pattern for source block. */ + srand(pattern_seed); + for (i = 0; i < SIZE_MB(2); i++) { + ((char *)src)[i] = (char) rand(); + } + + /* + * Unmap the beginning of dest so that the aligned address + * falls on no mapping. + */ + munmap(dest, SIZE_MB(1)); + + void *new_ptr = mremap(src + SIZE_MB(1), SIZE_MB(1), SIZE_MB(1), + MREMAP_MAYMOVE | MREMAP_FIXED, dest + SIZE_MB(1)); + if (new_ptr == MAP_FAILED) { + perror("mremap"); + success = 0; + goto out; + } + + /* Verify byte pattern after remapping */ + srand(pattern_seed); + for (i = 0; i < SIZE_MB(1); i++) { + char c = (char) rand(); + + if (((char *)src)[i] != c) { + ksft_print_msg("Data at src at %d got corrupted due to unrelated mremap\n", + i); + ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff, + ((char *) src)[i] & 0xff); + success = 0; + } + } + +out: + if (src && munmap(src, c.region_size) == -1) + perror("munmap src"); + + if (dest && munmap(dest, c.region_size) == -1) + perror("munmap dest"); + + if (success) + ksft_test_result_pass("%s\n", test_name); + else + ksft_test_result_fail("%s\n", test_name); +} + static void run_mremap_test_case(struct test test_case, int *failures, unsigned int threshold_mb, unsigned int pattern_seed) @@ -565,7 +643,7 @@ int main(int argc, char **argv) unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD; unsigned int pattern_seed; int num_expand_tests = 2; - int num_misc_tests = 1; + int num_misc_tests = 2; struct test test_cases[MAX_TEST] = {}; struct test perf_test_cases[MAX_PERF_TEST]; int page_size; @@ -666,6 +744,7 @@ int main(int argc, char **argv) fclose(maps_fp); mremap_move_within_range(pattern_seed); + mremap_move_1mb_from_start(pattern_seed); if (run_perf_tests) { ksft_print_msg("\n%s\n",