From patchwork Wed Oct 19 13:41:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mel Gorman X-Patchwork-Id: 5576 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:4ac7:0:0:0:0:0 with SMTP id y7csp351857wrs; Wed, 19 Oct 2022 07:15:56 -0700 (PDT) X-Google-Smtp-Source: AMsMyM7stxYEJZsmbkhQlJ5e04PiL17MS0EK/X+IATyV7201ZeJyMAf1YzHLLi0FnNsEz5xHjyA4 X-Received: by 2002:a63:c5d:0:b0:460:17cc:73a6 with SMTP id 29-20020a630c5d000000b0046017cc73a6mr7361140pgm.332.1666188956253; Wed, 19 Oct 2022 07:15:56 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666188956; cv=none; d=google.com; s=arc-20160816; b=LlD4oDX756ZqW8aOGIYVM9I6kjfD9CatS++BwRRBN6QTZeoYF5CmEZjCrWz0pFV2q5 +twpWNoOhys5M6jPQ5fURO0VPlHUpoNbYUWOt1AGnya057Ctu/XFG3hdFoZGJz82xyZh BIJEL/vHCRtys8YoRR2nhQzCwDAiRYCBcI57MnbHx6o8MR9t1qcGWImSUWUnQyxx0+NT Ub4iEK0tN71iqyxHEgX6RI/sbolNjsxXG3wiLRZIK5x6DHtYOPUxgcRCTABFWQRSkFd7 QTz1PRx69WmNKG89ribmGbtinwmWq4RVb9W54WbA3WWAGBfZJ6lXyuLqCXCu8MtG9KNc 2suQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-disposition:mime-version:message-id :subject:cc:to:from:date; bh=rJn//J1pXRveT53FH9urln0UwTyS7Ia5rO0K35g086Y=; b=eWZh8WY64xM4OFzZ3o13LoS9cPmxHuY6ChEIDTq7R00cKrdM9xSZ7H1Z2pPXlrCXW+ UtXVdh9/EfRFmMBja6WUc4nqBwEPXOrnSt5dvs7ZXGwob1jJ9vQlbQzOT5y9kckkUjid dqHww+l+Y9FfJPl4qXEEYiBJ/Fvrid9PM4ZMh5xVfSmQMHDj1RzukLcMwr5tw2GOa2NC UOqhKzc/yFqLoqZsH7LnsJx7YPtxhm5V219Xw1/H7NRvEgBkHYC+wHQf8FwnWcwO0jhy lwJr1+SwpaVRqdXxGjm3Sd0Q5LAAM4MtwGDMmg5V7019GojbNvhr9Sq5gQgpI4M4G77x GGqg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id j192-20020a638bc9000000b00462c469b730si18317687pge.648.2022.10.19.07.15.33; Wed, 19 Oct 2022 07:15:56 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233232AbiJSOCq (ORCPT + 99 others); Wed, 19 Oct 2022 10:02:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230150AbiJSOCU (ORCPT ); Wed, 19 Oct 2022 10:02:20 -0400 Received: from outbound-smtp03.blacknight.com (outbound-smtp03.blacknight.com [81.17.249.16]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ADDCFC148E for ; Wed, 19 Oct 2022 06:43:23 -0700 (PDT) Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp03.blacknight.com (Postfix) with ESMTPS id 46053C0E01 for ; Wed, 19 Oct 2022 14:41:58 +0100 (IST) Received: (qmail 28192 invoked from network); 19 Oct 2022 13:41:58 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.198.246]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 19 Oct 2022 13:41:57 -0000 Date: Wed, 19 Oct 2022 14:41:56 +0100 From: Mel Gorman To: Matthew Wilcox Cc: Andrew Morton , Linux-MM , LKML Subject: [RFC PATCH] mm/huge_memory: Do not clobber swp_entry_t during THP split Message-ID: <20221019134156.zjyyn5aownakvztf@techsingularity.net> MIME-Version: 1.0 Content-Disposition: inline X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747125751214577796?= X-GMAIL-MSGID: =?utf-8?q?1747125751214577796?= The following has been observed when running stressng mmap since commit b653db77350c ("mm: Clear page->private when splitting or migrating a page") watchdog: BUG: soft lockup - CPU#75 stuck for 26s! [stress-ng:9546] CPU: 75 PID: 9546 Comm: stress-ng Tainted: G E 6.0.0-revert-b653db77-fix+ #29 0357d79b60fb09775f678e4f3f64ef0579ad1374 Hardware name: SGI.COM C2112-4GP3/X10DRT-P-Series, BIOS 2.0a 05/09/2016 RIP: 0010:xas_descend+0x28/0x80 Code: cc cc 0f b6 0e 48 8b 57 08 48 d3 ea 83 e2 3f 89 d0 48 83 c0 04 48 8b 44 c6 08 48 89 77 18 48 89 c1 83 e1 03 48 83 f9 02 75 08 <48> 3d fd 00 00 00 76 08 88 57 12 c3 cc cc cc cc 48 c1 e8 02 89 c2 RSP: 0018:ffffbbf02a2236a8 EFLAGS: 00000246 RAX: ffff9cab7d6a0002 RBX: ffffe04b0af88040 RCX: 0000000000000002 RDX: 0000000000000030 RSI: ffff9cab60509b60 RDI: ffffbbf02a2236c0 RBP: 0000000000000000 R08: ffff9cab60509b60 R09: ffffbbf02a2236c0 R10: 0000000000000001 R11: ffffbbf02a223698 R12: 0000000000000000 R13: ffff9cab4e28da80 R14: 0000000000039c01 R15: ffff9cab4e28da88 FS: 00007fab89b85e40(0000) GS:ffff9cea3fcc0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fab84e00000 CR3: 00000040b73a4003 CR4: 00000000003706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: xas_load+0x3a/0x50 __filemap_get_folio+0x80/0x370 ? put_swap_page+0x163/0x360 pagecache_get_page+0x13/0x90 __try_to_reclaim_swap+0x50/0x190 scan_swap_map_slots+0x31e/0x670 get_swap_pages+0x226/0x3c0 folio_alloc_swap+0x1cc/0x240 add_to_swap+0x14/0x70 shrink_page_list+0x968/0xbc0 reclaim_page_list+0x70/0xf0 reclaim_pages+0xdd/0x120 madvise_cold_or_pageout_pte_range+0x814/0xf30 walk_pgd_range+0x637/0xa30 __walk_page_range+0x142/0x170 walk_page_range+0x146/0x170 madvise_pageout+0xb7/0x280 ? asm_common_interrupt+0x22/0x40 madvise_vma_behavior+0x3b7/0xac0 ? find_vma+0x4a/0x70 ? find_vma+0x64/0x70 ? madvise_vma_anon_name+0x40/0x40 madvise_walk_vmas+0xa6/0x130 do_madvise+0x2f4/0x360 __x64_sys_madvise+0x26/0x30 do_syscall_64+0x5b/0x80 ? do_syscall_64+0x67/0x80 ? syscall_exit_to_user_mode+0x17/0x40 ? do_syscall_64+0x67/0x80 ? syscall_exit_to_user_mode+0x17/0x40 ? do_syscall_64+0x67/0x80 ? do_syscall_64+0x67/0x80 ? common_interrupt+0x8b/0xa0 entry_SYSCALL_64_after_hwframe+0x63/0xcd The problem can be reproduced with the mmtests config config-workload-stressng-mmap. It does not always happen and when it triggers is variable but it has happened on multiple machines. The intent of commit b653db77350c patch was to avoid the case where PG_private is clear but folio->private is not-NULL. However, THP tail pages uses page->private for "swp_entry_t if folio_test_swapcache()" as stated in the documentation for struct folio. This patch only clobbers page->private for tail pages if the head page was not in swapcache and warns once if page->private had an unexpected value. Fixes: b653db77350c ("mm: Clear page->private when splitting or migrating a page") Signed-off-by: Mel Gorman Acked-by: Brian Foster --- mm/huge_memory.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 1cc4a5f4791e..03fc7e5edf07 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2455,7 +2455,16 @@ static void __split_huge_page_tail(struct page *head, int tail, page_tail); page_tail->mapping = head->mapping; page_tail->index = head->index + tail; - page_tail->private = 0; + + /* + * page->private should not be set in tail pages with the exception + * of swap cache pages that store the swp_entry_t in tail pages. + * Fix up and warn once if private is unexpectedly set. + */ + if (!folio_test_swapcache(page_folio(head))) { + VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); + page_tail->private = 0; + } /* Page flags must be visible before we make the page non-compound. */ smp_wmb();