linux-kernel - Re: [dm-devel] [stable][PATCH < 2.6.19] Fix data corruption with dm-crypt over RAID5

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Date:	Wed, 17 Jan 2007 00:44:08 -0800
From:	Piet Delaney <piet@...elane.com>
To:	device-mapper development <dm-devel@...hat.com>
Cc:	Piet Delaney <piet@...elane.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...l.org>,
	Chris Wright <chrisw@...s-sol.org>, dm-crypt@...ut.de,
	Andrey <dm-crypt-revealed-address@...ik.org>,
	Jens Axboe <jens.axboe@...cle.com>, agk@...hat.com
Subject: Re: [dm-devel] [stable][PATCH < 2.6.19] Fix data corruption with
	dm-crypt over RAID5

On Sat, 2006-12-02 at 03:27 +0100, Christophe Saout wrote:

Hi Christophe:

I'm wondering about trying out your patch with dm-crypt on 2.6.12. 
The code in drivers/md/dm-crypt.c`crypt_endio() appears to be the same.

Is there a reason that this isn't necessary or would be a bad idea.
Looks like the existing code isn't checking the BIO_UPTODATE flag
before doing the bio_put(). Looks the the second part of not calling
kcryptd_queue_io() and forwarding the processing to the cryptd is
effectively the same. The 1st change will set error if BIO_UPTODATE
isn't set and that will cause the 2nd change to skip calling 
kcryptd_queue_io().

I'm not sure about the change in the arg to bio_data_dir() 
changing from bio to io->bio. Perhaps they are equivalent;
care to comment on that.

Unless I hear otherwise I'll try it out Tomorrow.

-piet

> Fix corruption issue with dm-crypt on top of software raid5. Cancelled
> readahead bio's that report no error, just have BIO_UPTODATE cleared
> were reported as successful reads to the higher layers (and leaving
> random content in the buffer cache). Already fixed in 2.6.19.
> 
> Signed-off-by: Christophe Saout <christophe@...ut.de>
> 
> 
> --- linux-2.6.18.orig/drivers/md/dm-crypt.c	2006-09-20 05:42:06.000000000 +0200
> +++ linux-2.6.18/drivers/md/dm-crypt.c	2006-12-02 03:03:36.000000000 +0100
> @@ -717,13 +717,15 @@
>  	if (bio->bi_size)
>  		return 1;
>  
> +	if (!bio_flagged(bio, BIO_UPTODATE) && !error)
> +		error = -EIO;
> +                        
>  	bio_put(bio);
>  
>  	/*
>  	 * successful reads are decrypted by the worker thread
>  	 */
> -	if ((bio_data_dir(bio) == READ)
> -	    && bio_flagged(bio, BIO_UPTODATE)) {
> +	if (bio_data_dir(io->bio) == READ && !error) {
>  		kcryptd_queue_io(io);
>  		return 0;
>  	}
> 
> 
> --
> dm-devel mailing list
> dm-devel@...hat.com
> https://www.redhat.com/mailman/listinfo/dm-devel
-- 
Piet Delaney                                    Phone: (408) 200-5256
Blue Lane Technologies                          Fax:   (408) 200-5299
10450 Bubb Rd.
Cupertino, Ca. 95014                            Email: piet@...elane.com

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