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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C909EC32771 for ; Tue, 21 Jan 2020 01:49:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A73B322522 for ; Tue, 21 Jan 2020 01:49:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728794AbgAUBt2 (ORCPT ); Mon, 20 Jan 2020 20:49:28 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:57968 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728512AbgAUBt1 (ORCPT ); Mon, 20 Jan 2020 20:49:27 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1itifU-00CNBW-Pd; Tue, 21 Jan 2020 01:49:25 +0000 Date: Tue, 21 Jan 2020 01:49:24 +0000 From: Al Viro To: Namjae Jeon Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, valdis.kletnieks@vt.edu, hch@lst.de, sj1557.seo@samsung.com, pali.rohar@gmail.com, arnd@arndb.de, namjae.jeon@samsung.com Subject: Re: [PATCH v12 02/13] exfat: add super block operations Message-ID: <20200121014924.GI8904@ZenIV.linux.org.uk> References: <20200120124428.17863-1-linkinjeon@gmail.com> <20200120124428.17863-3-linkinjeon@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200120124428.17863-3-linkinjeon@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 20, 2020 at 09:44:17PM +0900, Namjae Jeon wrote: > +static void exfat_put_super(struct super_block *sb) > +{ > + struct exfat_sb_info *sbi = EXFAT_SB(sb); > + > + mutex_lock(&sbi->s_lock); > + if (test_and_clear_bit(EXFAT_SB_DIRTY, &sbi->s_state)) > + sync_blockdev(sb->s_bdev); > + exfat_set_vol_flags(sb, VOL_CLEAN); > + exfat_free_upcase_table(sb); > + exfat_free_bitmap(sb); > + mutex_unlock(&sbi->s_lock); > + > + if (sbi->nls_io) { > + unload_nls(sbi->nls_io); > + sbi->nls_io = NULL; > + } > + exfat_free_iocharset(sbi); > + sb->s_fs_info = NULL; > + kfree(sbi); > +} You need to RCU-delay freeing sbi and zeroing ->nls_io. *Everything* used by ->d_compare() and ->d_hash() needs that treatment. RCU-mode pathwalk can stray into a filesystem that has already been lazy-umounted and is just one close() away from shutdown. It's OK, as long as you make sure that all structures used in methods that could be called in RCU mode (->d_compare(), ->d_hash(), rcu-case ->d_revalidate(), rcu-case ->permission()) have destruction RCU-delayed. Look at what VFAT is doing; that's precisely the reason for that delayed_free() thing in there. > +static void exfat_destroy_inode(struct inode *inode) > +{ > + kmem_cache_free(exfat_inode_cachep, EXFAT_I(inode)); > +} No. Again, that MUST be RCU-delayed; either put an explicit call_rcu() here, or leave as-is, but make that ->free_inode(). > +static void __exit exit_exfat_fs(void) > +{ > + kmem_cache_destroy(exfat_inode_cachep); > + unregister_filesystem(&exfat_fs_type); ... and add rcu_barrier() here. > + exfat_cache_shutdown();