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Re: [PATCH 4/4 V3] xfsprogs: zero out clean log in xfs_metadump

To: Eric Sandeen <sandeen@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: [PATCH 4/4 V3] xfsprogs: zero out clean log in xfs_metadump
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Mon, 08 Jun 2015 13:46:37 -0500
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <5575AF7A.8050306@xxxxxxxxxxx>
References: <5568B7CE.9030709@xxxxxxxxxx> <5568BB5C.4080400@xxxxxxxxxxx> <5575AF7A.8050306@xxxxxxxxxxx>
When doing an obfuscated 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@xxxxxxxxxx>
---

V2: If not obfuscating, copy log as-is
V3: Remove pointless "obfuscate" checks after goto

diff --git a/db/metadump.c b/db/metadump.c
index bea4e00..bdc48a0 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 +2183,34 @@ copy_log(void)
                print_warning("cannot read log");
                return !stop_on_read_error;
        }
+
+       /* If not obfuscating, just copy the log as it is */
+       if (!obfuscate)
+               goto done;
+
+       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);
+               break;
+       case 1:
+               /* keep the dirty log */
+               print_warning(
+_("Filesystem log is dirty; image will contain unobfuscated metadata in 
log."));
+               break;
+       case -1:
+               /* log detection error */
+               print_warning(
+_("Could not discern log; image will contain unobfuscated metadata in log."));
+               break;
+       }
+
+done:
        return !write_buf(iocur_top);
 }
 

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