linux-ext4 - Re: [PATCH] ext4: don't set SB_RDONLY after filesystem errors

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Message-ID: <20240806-passt-weitgehend-6f1a0e7f3dbb@brauner>
Date: Tue, 6 Aug 2024 12:50:03 +0200
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>
Cc: Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] ext4: don't set SB_RDONLY after filesystem errors

On Mon, Aug 05, 2024 at 10:12:41PM GMT, Jan Kara wrote:
> When the filesystem is mounted with errors=remount-ro, we were setting
> SB_RDONLY flag to stop all filesystem modifications. We knew this misses
> proper locking (sb->s_umount) and does not go through proper filesystem
> remount procedure but it has been the way this worked since early ext2
> days and it was good enough for catastrophic situation damage
> mitigation. Recently, syzbot has found a way (see link) to trigger
> warnings in filesystem freezing because the code got confused by
> SB_RDONLY changing under its hands. Since these days we set
> EXT4_FLAGS_SHUTDOWN on the superblock which is enough to stop all
> filesystem modifications, modifying SB_RDONLY shouldn't be needed. So
> stop doing that.
> 
> Link: https://lore.kernel.org/all/000000000000b90a8e061e21d12f@google.com
> Reported-by: Christian Brauner <brauner@...nel.org>
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---

Thank you!
Reviewed-by: Christian Brauner <brauner@...nel.org>