Re: [PATCH 1/7] fsfreeze: Prevent emergency thaw from looping infinitely

[Jan Kara <jack@suse.cz>]

On Tue 10-07-12 17:20:57, Fernando Luis Vázquez Cao wrote:
> The thawing of a filesystem through sysrq-j loops infinitely as it
> incorrectly detects a thawed filesytsem as frozen and tries to
> unfreeze repeatedly. This is a regression caused by
> 4504230a71566785a05d3e6b53fa1ee071b864eb ("freeze_bdev: grab active
> reference to frozen superblocks") in that it no longer returned
> -EINVAL for superblocks that were not frozen.
  Umm, I don't think above mentioned commit is really guilty. Also I think
your patch breaks thawing of a block device without mounted filesystem -
you end up returning EINVAL for that...

								Honza
> 
> Return -EINVAL when the filesystem is already unfrozen to avoid this
> problem.
> 
> Cc: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> ---
> 
> diff -urNp linux-3.5-rc4-orig/fs/block_dev.c linux-3.5-rc4/fs/block_dev.c
> --- linux-3.5-rc4-orig/fs/block_dev.c	2012-06-27 12:00:47.694616000 +0900
> +++ linux-3.5-rc4/fs/block_dev.c	2012-06-29 13:38:23.841352532 +0900
> @@ -319,22 +319,20 @@ int thaw_bdev(struct block_device *bdev,
>  	if (!bdev->bd_fsfreeze_count)
>  		goto out;
>  
> -	error = 0;
> -	if (--bdev->bd_fsfreeze_count > 0)
> +	if (--bdev->bd_fsfreeze_count > 0) {
> +		error = 0;
>  		goto out;
> +	}
>  
>  	if (!sb)
>  		goto out;
>  
>  	error = thaw_super(sb);
> -	if (error) {
> +	if (error)
>  		bdev->bd_fsfreeze_count++;
> -		mutex_unlock(&bdev->bd_fsfreeze_mutex);
> -		return error;
> -	}
>  out:
>  	mutex_unlock(&bdev->bd_fsfreeze_mutex);
> -	return 0;
> +	return error;
>  }
>  EXPORT_SYMBOL(thaw_bdev);
>  
> 
> 
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-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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