linux-kernel - Re: [PATCH] ext3: Don't update superblock write time when filesystem is read-only

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Date:	Mon, 5 Oct 2009 14:24:09 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Jan Kara <jack@...e.cz>,
	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	sandeen@...hat.com
Subject: Re: [PATCH] ext3: Don't update superblock write time when
	filesystem is read-only

On Sat 03-10-09 23:12:38, Theodore Ts'o wrote:
> This avoids updating the superblock write time when we are mounting
> the root file system read/only but we need to replay the journal; at
> that point, for people who are east of GMT and who make their clock
> tick in localtime for Windows bug-for-bug compatibility, and this will
> cause e2fsck to complain and force a full file system check.
  Thanks, the patch is queued in my queue already. I just held it for a
while because Eric also had a valid point - maybe fsck is too strict when
it forces a full filesystem check just because the superblock write time is
in future? On a pc-class hw, clocks go often wrong. Even I remember setting
system clock on my desktop a few hours back because it just gets out of
sync and I don't run NTP...
  So I'm not against your patch because it can help in some cases and
it's not a big deal but I think a proper fix would be in fsck...

								Honza
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  fs/ext3/super.c |   13 ++++++++++++-
>  1 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/ext3/super.c b/fs/ext3/super.c
> index 72743d3..7a520a8 100644
> --- a/fs/ext3/super.c
> +++ b/fs/ext3/super.c
> @@ -2321,7 +2321,18 @@ static int ext3_commit_super(struct super_block *sb,
>  
>  	if (!sbh)
>  		return error;
> -	es->s_wtime = cpu_to_le32(get_seconds());
> +	/*
> +	 * If the file system is mounted read-only, don't update the
> +	 * superblock write time.  This avoids updating the superblock
> +	 * write time when we are mounting the root file system
> +	 * read/only but we need to replay the journal; at that point,
> +	 * for people who are east of GMT and who make their clock
> +	 * tick in localtime for Windows bug-for-bug compatibility,
> +	 * the clock is set in the future, and this will cause e2fsck
> +	 * to complain and force a full file system check.
> +	 */
> +	if (!(sb->s_flags & MS_RDONLY))
> +		es->s_wtime = cpu_to_le32(get_seconds());
>  	es->s_free_blocks_count = cpu_to_le32(ext3_count_free_blocks(sb));
>  	es->s_free_inodes_count = cpu_to_le32(ext3_count_free_inodes(sb));
>  	BUFFER_TRACE(sbh, "marking dirty");
> -- 
> 1.6.4.4.2.g31f8e.dirty
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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