From: Theodore Ts'o Subject: Re: [PATCH] ext4: do not try to write superblock on journal-less readonly remount Date: Tue, 25 Dec 2012 14:09:47 -0500 Message-ID: <20121225190947.GA16669@thunk.org> References: <1351154397-14743-1-git-send-email-mjt@msgid.tls.msk.ru> <50D025FE.5040201@msgid.tls.msk.ru> <50D089A2.8030809@redhat.com> <50D2D959.9060300@msgid.tls.msk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , linux-ext4@vger.kernel.org To: Michael Tokarev Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:40306 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754082Ab2LYTJy (ORCPT ); Tue, 25 Dec 2012 14:09:54 -0500 Content-Disposition: inline In-Reply-To: <50D2D959.9060300@msgid.tls.msk.ru> Sender: linux-ext4-owner@vger.kernel.org List-ID: OK, I'll take this; I'm going to take your suggestion and only call ext4_commit_super() when we are going from a read-write to read-only mount, since that's the only time when we need to force that the superblock be written out. - Ted commit 86fffe43a74af16e306896eba8210bebd33bfd1f Author: Michael Tokarev Date: Tue Dec 25 14:08:16 2012 -0500 ext4: do not try to write superblock on ro remount w/o journal When a journal-less ext4 filesystem is mounted on a read-only block device (blockdev --setro will do), each remount (for other, unrelated, flags, like suid=>nosuid etc) results in a series of scary messages from kernel telling about I/O errors on the device. This is becauese of the following code ext4_remount(): if (sbi->s_journal == NULL) ext4_commit_super(sb, 1); at the end of remount procedure, which forces writing (flushing) of a superblock regardless whenever it is dirty or not, if the filesystem is readonly or not, and whenever the device itself is readonly or not. We only need call ext4_commit_super when the file system had been previously mounted read/write. Thanks to Eric Sandeen for help in diagnosing this issue. Cc: stable@vger.kernel.org Signed-off-By: Michael Tokarev Signed-off-by: "Theodore Ts'o" diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 4969167..183ae34 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4729,7 +4729,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) } ext4_setup_system_zone(sb); - if (sbi->s_journal == NULL) + if (sbi->s_journal == NULL && !(old_sb_flags & MS_RDONLY)) ext4_commit_super(sb, 1); #ifdef CONFIG_QUOTA