From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7538113C3F2 for ; Sat, 22 Feb 2025 07:41:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740210086; cv=none; b=YHW3R3t3jbb2hcBqx0XwQ/7TsH8k6lrgIBhYzBNYA8BGsvAsQJAfd6Kn75d8DHHeGjsGxnOcAR7GVfnWaxpsMIYoZdRZBmgOkZloJqZS0UNbk2NbgDSmHiFQGDR8vGDoP6ZkSacPwtEu7HnMK+kz6eBU00L6fQES811Z6U8b9QQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740210086; c=relaxed/simple; bh=3h/oOXxNyk1GeCkXR31OeqcPgDyLOpqYMRTuUwVtpDQ=; h=Message-ID:Date:MIME-Version:CC:Subject:To:References:From: In-Reply-To:Content-Type; b=RYeVlR0fMZVfZn41gLcBfYtYXaJhno05N+rDh/f9hFuvhev6cpxF8uLLoEY52F3f1ECmPRkbvpAuJ3f6Z3ZM9IQDZ7MDmaEAUsAyZgqYP38rUXP+qjzadwPIzqCJFsa9uuY34CatTOxaIyImOEJvRKaQfAvd/hICIeNJyjeK5Fw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.234]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Z0Jjs50Nwz2JYZX; Sat, 22 Feb 2025 15:37:21 +0800 (CST) Received: from kwepemg100017.china.huawei.com (unknown [7.202.181.58]) by mail.maildlp.com (Postfix) with ESMTPS id 23C7E140155; Sat, 22 Feb 2025 15:41:20 +0800 (CST) Received: from [10.174.178.114] (10.174.178.114) by kwepemg100017.china.huawei.com (7.202.181.58) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Sat, 22 Feb 2025 15:41:18 +0800 Message-ID: Date: Sat, 22 Feb 2025 15:41:18 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird CC: , , , , , , , , , , , , , , Subject: Re: [PATCH] mm: swap: Avoid infinite loop if no valid swap entry found during do_swap_page To: References: <20250222024617.2790609-1-mawupeng1@huawei.com> From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemg100017.china.huawei.com (7.202.181.58) On 2025/2/22 15:33, Kairui Song wrote: > On Sat, Feb 22, 2025 at 10:56 AM Wupeng Ma wrote: >> >> From: Ma Wupeng >> >> During our test, infinite loop is produced during #PF will lead to infinite >> error log as follow: >> >> get_swap_device: Bad swap file entry 114000000 >> >> Digging into the source, we found that the swap entry is invalid due to >> unknown reason, and this lead to invalid swap_info_struct. Excessive log > > Hi Wupeng, > > What is the kernel version you are using? If it's another bug causing > this invalid swap entry, we should fix that bug instead, not > workaround it. > > This looks kind of similar to another PATCH & Bug report, corrupted > page table or swap entry: > https://lore.kernel.org/linux-mm/e223b0e6ba2f4924984b1917cc717bd5@honor.com/ > > Might be the same kernel bug? Gaoxu mentioned the bug was observed on > Kernel 6.6.30 (android version), and neither of these two workarounds > will fix it completely, the invalid value could cause many other > issues too. We definitely need to find out the root cause. We are having this problem in linux-v5.10, since the log is lost and swap is not enabled in this machines, maybe memory corrupted in the pt. > >> printing can fill up the prioritized log space, leading to the purging of >> originally valid logs and hindering problem troubleshooting. To make this >> more robust, kill this task. >> >> Signed-off-by: Ma Wupeng >> --- >> include/linux/swap.h | 1 + >> mm/memory.c | 9 ++++++++- >> mm/swapfile.c | 2 +- >> 3 files changed, 10 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/swap.h b/include/linux/swap.h >> index b13b72645db3..0fa39cf66bc4 100644 >> --- a/include/linux/swap.h >> +++ b/include/linux/swap.h >> @@ -508,6 +508,7 @@ struct backing_dev_info; >> extern int init_swap_address_space(unsigned int type, unsigned long nr_pages); >> extern void exit_swap_address_space(unsigned int type); >> extern struct swap_info_struct *get_swap_device(swp_entry_t entry); >> +struct swap_info_struct *_swap_info_get(swp_entry_t entry); >> sector_t swap_folio_sector(struct folio *folio); >> >> static inline void put_swap_device(struct swap_info_struct *si) >> diff --git a/mm/memory.c b/mm/memory.c >> index b4d3d4893267..2d36e5a644d1 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -4365,8 +4365,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) >> >> /* Prevent swapoff from happening to us. */ >> si = get_swap_device(entry); >> - if (unlikely(!si)) >> + if (unlikely(!si)) { >> + if (unlikely(!_swap_info_get(entry))) >> + /* >> + * return VM_FAULT_SIGBUS for invalid swap entry to >> + * avoid infinite #PF. >> + */ >> + ret = VM_FAULT_SIGBUS; > > This could lead to VM_FAULT_SIGBUS on swapoff. After swapoff > get_swap_device will return NULL. If swap is off, All swap pages should be swap in as expected, so such entry can not trigger do_swap_page?