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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 371B2C7EE23 for ; Mon, 15 May 2023 17:14:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243439AbjEORO5 (ORCPT ); Mon, 15 May 2023 13:14:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243725AbjEOROb (ORCPT ); Mon, 15 May 2023 13:14:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20EF35BA3 for ; Mon, 15 May 2023 10:12:55 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6726762B5C for ; Mon, 15 May 2023 17:12:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26C18C433D2; Mon, 15 May 2023 17:12:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1684170749; bh=lDTQYbdc1BGD6M667YgLb39vXyQ/4IshAFZ7gVNmv8o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p1ZGmU4Jxi2komr/7La7AIVKdhTYGOr2nZFsR1arYfwR2JL1LPyXcdRhhdHOCPAPY aqAImgCgLmfSWHu4DDH5Pn5YQdvT9JffghEWxEjGL61dQ41rbZl9OoiSKvekdO5CHZ DLhc7qBzP4k8Cy1uE+f4IyDUk0Bn0BCEdU0zvBpM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable@kernel.org, syzbot+6b7df7d5506b32467149@syzkaller.appspotmail.com, Jan Kara , Christian Brauner , Theodore Tso Subject: [PATCH 6.1 229/239] ext4: fix lockdep warning when enabling MMP Date: Mon, 15 May 2023 18:28:12 +0200 Message-Id: <20230515161728.583672604@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230515161721.545370111@linuxfoundation.org> References: <20230515161721.545370111@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jan Kara commit 949f95ff39bf188e594e7ecd8e29b82eb108f5bf upstream. When we enable MMP in ext4_multi_mount_protect() during mount or remount, we end up calling sb_start_write() from write_mmp_block(). This triggers lockdep warning because freeze protection ranks above s_umount semaphore we are holding during mount / remount. The problem is harmless because we are guaranteed the filesystem is not frozen during mount / remount but still let's fix the warning by not grabbing freeze protection from ext4_multi_mount_protect(). Cc: stable@kernel.org Reported-by: syzbot+6b7df7d5506b32467149@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=ab7e5b6f400b7778d46f01841422e5718fb81843 Signed-off-by: Jan Kara Reviewed-by: Christian Brauner Link: https://lore.kernel.org/r/20230411121019.21940-1-jack@suse.cz Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/mmp.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) --- a/fs/ext4/mmp.c +++ b/fs/ext4/mmp.c @@ -39,28 +39,36 @@ static void ext4_mmp_csum_set(struct sup * Write the MMP block using REQ_SYNC to try to get the block on-disk * faster. */ -static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) +static int write_mmp_block_thawed(struct super_block *sb, + struct buffer_head *bh) { struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data); - /* - * We protect against freezing so that we don't create dirty buffers - * on frozen filesystem. - */ - sb_start_write(sb); ext4_mmp_csum_set(sb, mmp); lock_buffer(bh); bh->b_end_io = end_buffer_write_sync; get_bh(bh); submit_bh(REQ_OP_WRITE | REQ_SYNC | REQ_META | REQ_PRIO, bh); wait_on_buffer(bh); - sb_end_write(sb); if (unlikely(!buffer_uptodate(bh))) return -EIO; - return 0; } +static int write_mmp_block(struct super_block *sb, struct buffer_head *bh) +{ + int err; + + /* + * We protect against freezing so that we don't create dirty buffers + * on frozen filesystem. + */ + sb_start_write(sb); + err = write_mmp_block_thawed(sb, bh); + sb_end_write(sb); + return err; +} + /* * Read the MMP block. It _must_ be read from disk and hence we clear the * uptodate flag on the buffer. @@ -346,7 +354,11 @@ skip: seq = mmp_new_seq(); mmp->mmp_seq = cpu_to_le32(seq); - retval = write_mmp_block(sb, bh); + /* + * On mount / remount we are protected against fs freezing (by s_umount + * semaphore) and grabbing freeze protection upsets lockdep + */ + retval = write_mmp_block_thawed(sb, bh); if (retval) goto failed;