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]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD9D2C433F5 for ; Wed, 25 May 2022 06:40:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0E94C8D0003; Wed, 25 May 2022 02:40:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0985A8D0001; Wed, 25 May 2022 02:40:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EEB198D0003; Wed, 25 May 2022 02:40:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id DF1D48D0001 for ; Wed, 25 May 2022 02:40:46 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id A67C120A71 for ; Wed, 25 May 2022 06:40:46 +0000 (UTC) X-FDA: 79503317292.27.745A36D Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf07.hostedemail.com (Postfix) with ESMTP id E693440007 for ; Wed, 25 May 2022 06:40:34 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4L7Lz24Nf5zjWy0; Wed, 25 May 2022 14:39:58 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 25 May 2022 14:40:40 +0800 Subject: Re: [PATCH v4 4/5] mm/shmem: fix infinite loop when swap in shmem error at swapoff time To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: "akpm@linux-foundation.org" , "hughd@google.com" , "willy@infradead.org" , "vbabka@suse.cz" , "dhowells@redhat.com" , "neilb@suse.de" , "apopple@nvidia.com" , "david@redhat.com" , "surenb@google.com" , "peterx@redhat.com" , "rcampbell@nvidia.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20220519125030.21486-1-linmiaohe@huawei.com> <20220519125030.21486-5-linmiaohe@huawei.com> <20220525043233.GA808704@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: Date: Wed, 25 May 2022 14:40:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220525043233.GA808704@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Authentication-Results: imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Stat-Signature: cmsrwx1heddyqyb5a38okx481u7wsr1j X-Rspamd-Queue-Id: E693440007 X-Rspamd-Server: rspam01 X-HE-Tag: 1653460834-348683 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/5/25 12:32, HORIGUCHI NAOYA(堀口 直也) wrote: > On Thu, May 19, 2022 at 08:50:29PM +0800, Miaohe Lin wrote: >> When swap in shmem error at swapoff time, there would be a infinite loop >> in the while loop in shmem_unuse_inode(). It's because swapin error is >> deliberately ignored now and thus info->swapped will never reach 0. So >> we can't escape the loop in shmem_unuse(). >> >> In order to fix the issue, swapin_error entry is stored in the mapping >> when swapin error occurs. So the swapcache page can be freed and the >> user won't end up with a permanently mounted swap because a sector is >> bad. If the page is accessed later, the user process will be killed >> so that corrupted data is never consumed. On the other hand, if the >> page is never accessed, the user won't even notice it. >> >> Reported-by: Naoya Horiguchi >> Signed-off-by: Miaohe Lin >> --- > > ... >> @@ -1672,6 +1676,36 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp, >> return error; >> } >> >> +static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index, >> + struct folio *folio, swp_entry_t swap) >> +{ >> + struct address_space *mapping = inode->i_mapping; >> + struct shmem_inode_info *info = SHMEM_I(inode); >> + swp_entry_t swapin_error; >> + void *old; >> + >> + swapin_error = make_swapin_error_entry(&folio->page); >> + old = xa_cmpxchg_irq(&mapping->i_pages, index, >> + swp_to_radix_entry(swap), >> + swp_to_radix_entry(swapin_error), 0); >> + if (old != swp_to_radix_entry(swap)) >> + return; >> + >> + folio_wait_writeback(folio); >> + delete_from_swap_cache(&folio->page); >> + spin_lock_irq(&info->lock); >> + /* >> + * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks won't >> + * be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in >> + * shmem_evict_inode. >> + */ >> + info->alloced--; >> + info->swapped--; > > I'm not familiar with folio yet and might miss some basic thing, > but is it OK to decrement by one instead of folio_nr_pages()? info->swapped is also decremented by one in shmem_swapin_folio(). In fact, no huge page swapin is supported yet (this is also true for non-shmem case). So I think info->swapped-- should be OK. Or am I miss something? > > Thanks, > Naoya Horiguchi Many thanks for review and comment! It's really helpful! :) >