linux-kernel - Re: [PATCH v6] e2fsck: Correct ext4 dates generated by old kernels.

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Message-ID: <1385762083.20396.48.camel@chiang>
Date:	Fri, 29 Nov 2013 16:54:43 -0500
From:	David Turner <novalis@...alis.org>
To:	Mark Harris <mhlk@....us>
Cc:	Andreas Dilger <adilger@...ger.ca>, Theodore Ts'o <tytso@....edu>,
	Jan Kara <jack@...e.cz>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6] e2fsck: Correct ext4 dates generated by old kernels.

Is this version good, or should I make some more improvements?

On Thu, 2013-11-14 at 16:06 -0500, David Turner wrote:
> Not sure what the official subject line format is for revising only 
> one of N patches, so I'm trying this one.  Let me now if it is wrong.
> 
> On Thu, 2013-11-14 at 02:15 -0800, Mark Harris wrote:
> > > + * mis-encoded.
> > > + */
> > > +#define EXT4_EXTRA_NEGATIVE_DATE_CUTOFF 5 * (1ULL << 32)
> > 
> > Wouldn't 2242 be 0x200000000ULL, i.e. 2 * (1ULL << 32)?
> 
> Actually, it would be 2 * (1LL << 32), because we later use it in a
> comparison with a signed value.  
> 
> --
> Older kernels on 64-bit machines would incorrectly encode pre-1970
> ext4 dates as post-2311 dates.  Detect and correct this (assuming the
> current date is before 2242).
> 
> Signed-off-by: David Turner <novalis@...alis.org>
> ---
>  e2fsck/pass1.c   | 41 +++++++++++++++++++++++++++++++++++++++++
>  e2fsck/problem.c |  4 ++++
>  e2fsck/problem.h |  4 ++++
>  3 files changed, 49 insertions(+)
> 
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index ab23e42..e19855f 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -348,6 +348,24 @@ fix:
>  				EXT2_INODE_SIZE(sb), "pass1");
>  }
>  
> +#define EXT4_EPOCH_BITS 2
> +#define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)
> +
> +static int check_inode_extra_negative_epoch(__u32 xtime, __u32 extra) {
> +	return (xtime & (1 << 31)) != 0 &&
> +		(extra & EXT4_EPOCH_MASK) == EXT4_EPOCH_MASK;
> +}
> +
> +#define CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, xtime) \
> +	check_inode_extra_negative_epoch(inode->i_##xtime, \
> +					 inode->i_##xtime##_extra)
> +
> +/* When today's date is earlier than 2242, we assume that atimes,
> + * ctimes, and mtimes with years in the range 2310..2378 are actually
> + * pre-1970 dates mis-encoded.
> + */
> +#define EXT4_EXTRA_NEGATIVE_DATE_CUTOFF 2 * (1LL << 32)
> +
>  static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
>  {
>  	struct ext2_super_block *sb = ctx->fs->super;
> @@ -388,6 +406,29 @@ static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
>  		/* it seems inode has an extended attribute(s) in body */
>  		check_ea_in_inode(ctx, pctx);
>  	}
> +
> +	/*
> +	 * If the inode's extended atime (ctime, mtime) is stored in
> +	 * the old, invalid format, repair it. 
> +	 */
> +	if (sizeof(time_t) > 4 && ctx->now < EXT4_EXTRA_NEGATIVE_DATE_CUTOFF &&
> +	    (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, atime) ||
> +	     CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, ctime) ||
> +	     CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, mtime))) {
> +
> +		if (!fix_problem(ctx, PR_1_EA_TIME_OUT_OF_RANGE, pctx))
> +			return;
> +
> +		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, atime))
> +			inode->i_atime_extra &= ~EXT4_EPOCH_MASK;
> +		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, ctime))
> +			inode->i_ctime_extra &= ~EXT4_EPOCH_MASK;
> +		if (CHECK_INODE_EXTRA_NEGATIVE_EPOCH(inode, mtime))
> +			inode->i_mtime_extra &= ~EXT4_EPOCH_MASK;
> +		e2fsck_write_inode_full(ctx, pctx->ino, pctx->inode,
> +					EXT2_INODE_SIZE(sb), "pass1");
> +	}
> +
>  }
>  
>  /*
> diff --git a/e2fsck/problem.c b/e2fsck/problem.c
> index 897693a..b212d00 100644
> --- a/e2fsck/problem.c
> +++ b/e2fsck/problem.c
> @@ -1018,6 +1018,10 @@ static struct e2fsck_problem problem_table[] = {
>  	  N_("@i %i, end of extent exceeds allowed value\n\t(logical @b %c, physical @b %b, len %N)\n"),
>  	  PROMPT_CLEAR, 0 },
>  
> +  /* Timestamp(s) on inode beyond 2310-04-04 are likely pre-1970 dates. */
> +	{ PR_1_EA_TIME_OUT_OF_RANGE,
> +		N_("Timestamp(s) on @i %i beyond 2310-04-04 are likely pre-1970 dates.\n"),
> +		PROMPT_FIX | PR_PREEN_OK | PR_NO_OK, 0 },
>  
>  	/* Pass 1b errors */
>  
> diff --git a/e2fsck/problem.h b/e2fsck/problem.h
> index ae1ed26..3710638 100644
> --- a/e2fsck/problem.h
> +++ b/e2fsck/problem.h
> @@ -593,6 +593,10 @@ struct problem_context {
>  #define PR_1_EXTENT_INDEX_START_INVALID	0x01006D
>  
>  #define PR_1_EXTENT_END_OUT_OF_BOUNDS	0x01006E
> +
> +/* Timestamp(s) on inode beyond 2310-04-04 are likely pre-1970 dates. */
> +#define PR_1_EA_TIME_OUT_OF_RANGE	0x01006F
> +
>  /*
>   * Pass 1b errors
>   */


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