Re: [PATCH 4/4] xfsprogs: zero out clean log in xfs_metadump

[Brian Foster <bfoster@redhat.com>]

On Fri, May 29, 2015 at 02:17:48PM -0500, Eric Sandeen wrote:
> When doing an xfs_metadump, if the log is clean, zero it out
> for 2 reasons:
> 
>  * It'll make the image more compressible
>  * It'll eliminate an un-obfuscated metadata source
> 
> If the log isn't clean, and the user expected obfuscation, warn
> that metadata in the log will not be obfuscated.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/db/metadump.c b/db/metadump.c
> index bea4e00..eb5e9da 100644
> --- a/db/metadump.c
> +++ b/db/metadump.c
> @@ -17,6 +17,7 @@
>   */
>  
>  #include <libxfs.h>
> +#include <libxlog.h>
>  #include "bmap.h"
>  #include "command.h"
>  #include "metadump.h"
> @@ -2169,6 +2170,8 @@ copy_sb_inodes(void)
>  static int
>  copy_log(void)
>  {
> +	int dirty;
> +
>  	if (show_progress)
>  		print_progress("Copying log");
>  
> @@ -2180,6 +2183,31 @@ copy_log(void)
>  		print_warning("cannot read log");
>  		return !stop_on_read_error;
>  	}
> +
> +	dirty = xlog_is_dirty(mp, &x, 0);
> +
> +	switch (dirty) {
> +	case 0:
> +		/* clear out a clean log */
> +		if (show_progress)
> +			print_progress("Zeroing clean log");
> +		memset(iocur_top->data, 0,
> +			mp->m_sb.sb_logblocks * mp->m_sb.sb_blocksize);

Hmm, so is there any reason in the future we might want a metadump with
a clean log matching what is actually on-disk? This is a debug tool
after all. Perhaps this is mainly covered by the unclean and/or error
cases, but that still seems like a potential loss of capability.

Anyways, I'm wondering if we should have an 'if (obfuscate)' here.
Thoughts?

Brian

> +		break;
> +	case 1:
> +		/* keep the dirty log */
> +		if (obfuscate)
> +			print_warning(
> +_("Filesystem log is dirty; image will contain unobfuscated metadata in log."));
> +		break;
> +	case -1:
> +		/* log detection error */
> +		if (obfuscate)
> +			print_warning(
> +_("Could not discern log; image will contain unobfuscated metadata in log."));
> +		break;
> +	}
> +
>  	return !write_buf(iocur_top);
>  }
>  
> 
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