From: Jan Kara <jack@suse.cz>
To: Daeho Jeong <daeho.jeong@samsung.com>
Cc: tytso@mit.edu, linux-ext4@vger.kernel.org,
Kitae Lee <kitae87.lee@samsung.com>
Subject: Re: [PATCH] ext4: guarantee already started handles to successfully finish while ro remounting
Date: Thu, 5 May 2016 15:45:11 +0200 [thread overview]
Message-ID: <20160505134511.GH1970@quack2.suse.cz> (raw)
In-Reply-To: <1462150237-20701-1-git-send-email-daeho.jeong@samsung.com>
On Mon 02-05-16 09:50:37, Daeho Jeong wrote:
> We check whether a new handle can be started through
> ext4_journal_check_start() and the function refuses to start the handle
> when the filesystem is mounted with read-only. But now, when we remount
> the filesystem with read-only option, already started handles are
> allowed to be written on disk, but the subsequent metadata modification
> using the handles are refused by ext4_journal_check_start().
>
> As an example, in ext4_evict_inode(), i_size can be set to 0 using
> a successfully started handle, but, when we remount the filesystem
> with read-only option at that time, the subsequent ext4_truncate()
> will be failed and the filesystem integrity will be damaged.
>
> Therefore, we need to permit the metadata modification using already
> started handles to be proceeded, even if s_flags of the filesystem is
> set to MS_RDONLY.
>
> Kitae found the problem and suggested the solution.
So can you share a reproducer for this issue? Because my initial thinking
is that checks during remount should fail the remount with EBUSY if there
is any modification outstanding... If they don't we have a racy remount and
fs-freezing code, which is a bug.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2016-05-05 13:45 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-02 0:50 [PATCH] ext4: guarantee already started handles to successfully finish while ro remounting Daeho Jeong
2016-05-05 13:45 ` Jan Kara [this message]
2016-05-05 15:44 ` Theodore Ts'o
2016-05-06 5:35 Daeho Jeong
2016-05-06 6:01 Daeho Jeong
2016-05-06 13:00 ` Theodore Ts'o
2016-05-06 20:01 ` Andreas Dilger
2016-05-06 23:36 ` tytso
2016-05-09 8:40 ` Jan Kara
2016-05-07 13:05 Daeho Jeong
2016-05-07 17:47 ` Theodore Ts'o
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