Re: [PATCH 8/17] fsfreeze: allow bdev level thaws when the sb is unfrozen

[Jan Kara <jack@suse.cz>]

On Mon 07-01-13 20:32:13, Fernando Luis Vázquez Cao wrote:
> This behavior is important in a scenario where a filesystem frozen using
> freeze_bdev() is thawed through the superblock level API; if we
> caused subsequent calls to thaw_bdev() future calls to freeze_bdev()
> would fail to freeze the superblock.
> 
> We can get rid of this code away once bdev level fsfreeze and sb level
> fsfreeze are properly integrated.
  OK, makes sence. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

								Honza
> 
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Josef Bacik <jbacik@fusionio.com>
> Cc: Eric Sandeen <sandeen@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Dave Chinner <dchinner@redhat.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
> ---
> 
> diff -urNp linux-3.8-rc1-orig/fs/block_dev.c linux-3.8-rc1/fs/block_dev.c
> --- linux-3.8-rc1-orig/fs/block_dev.c	2012-12-25 11:52:04.344018000 +0900
> +++ linux-3.8-rc1/fs/block_dev.c	2012-12-25 16:11:12.648018000 +0900
> @@ -272,8 +272,19 @@ int thaw_bdev(struct block_device *bdev,
>  	}
>  
>  	error = thaw_super(sb);
> -	if (error)
> +	/*
> +	 * If the superblock is already unfrozen, i.e. thaw_super() returned
> +	 * -EINVAL, we consider the block device level thaw successful. This
> +	 * behavior is important in a scenario where a filesystem frozen using
> +	 * freeze_bdev() is thawed through the superblock level API; if we
> +	 * caused the subsequent thaw_bdev() to fail bdev->bd_fsfreeze_count
> +	 * would not go back to 0 which means that future calls to freeze_bdev()
> +	 * would not freeze the superblock, just increase the counter.
> +	 */
> +	if (error && error != -EINVAL)
>  		bdev->bd_fsfreeze_count++;
> +	else
> +		error = 0;
>  out:
>  	mutex_unlock(&bdev->bd_fsfreeze_mutex);
>  	return error;
> 
> 
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR
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