Re: [PATCH] Refuse to install on XFS destroying its superblock

[Vladimir 'phcoder' Serbinenko]

Robert Millan wrote:
> On Fri, Oct 16, 2009 at 11:08:31PM +0200, Vladimir 'phcoder' Serbinenko wrote:
>   
>> Robert Millan wrote:
>>     
>>> On Fri, Oct 16, 2009 at 10:09:41PM +0200, Vladimir 'phcoder' Serbinenko 
>>> wrote:
>>>   
>>>       
>>>> Robert Millan wrote:
>>>>     
>>>>         
>>>>> On Fri, Oct 16, 2009 at 06:01:56PM +0200, Jordi Mallach wrote:
>>>>>   
>>>>>       
>>>>>           
>>>>>> On Fri, Oct 16, 2009 at 04:03:01PM +0200, Vladimir 'phcoder' Serbinenko 
>>>>>> wrote:
>>>>>>     
>>>>>>         
>>>>>>             
>>>>>>> +  if (memcmp (tmp_img, "XFSB", 4) == 0)
>>>>>>> +    grub_util_error ("Can't install on XFS.");
>>>>>>>       
>>>>>>>           
>>>>>>>               
>>>>>> Can this error message give some more detail on what the problem is?
>>>>>>     
>>>>>>         
>>>>>>             
>>>>> I suggest something like:
>>>>>
>>>>>   grub_util_warn ("Refusing to overwrite XFS meta-data.");
>>>>>
>>>>> This is more informative, and with grub_util_warn() user has an 
>>>>> opportunity to
>>>>> override it if she knows what she's doing.
>>>>>
>>>>>   
>>>>>       
>>>>>           
>>>> Installing with blocklists/to partition is considered
>>>> backward-compatibility feature. We never supported a config with XFS why
>>>> we would want bw-compat for it?
>>>>     
>>>>         
>>> Because we can't reliably tell if it's a config with XFS, only the user can.
>>> This is an issue for both MBR or PBR installs.
>>>
>>> Maybe "XFSB" is only a remnant from one of this disk / partition former
>>> lifes.  Maybe it's a valid XFS but user no longer cares about it.  Or
>>> maybe a DOS-style label was created on top of it, without overwriting the 
>>> first
>>> 440 bytes.  Or maybe another filesystem had overwritten most XFS metadata
>>> but preserved the first block (this is conceivable since other filesystems
>>> tend to avoid using the first block).
>>>
>>> If user has to workaround GRUB heuristics by dd'ing zeros into a partition
>>> before running grub-install, this is a sign GRUB isn't doing the right 
>>> thing.
>>>
>>>   
>>>       
>> Well, ok. But then I would ask to use a separate --force e.g.
>> --force-destroy-xfs since users and distributions tend to use --force
>> too much
>>     
>
> Ok.
>
>   


-- 
Regards
Vladimir 'phcoder' Serbinenko
Personal git repository: http://repo.or.cz/w/grub2/phcoder.git 

diff --git a/ChangeLog b/ChangeLog
index 960fc06..cc225a7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2009-10-16  Vladimir Serbinenko  <address@hidden>
 
+       * util/i386/pc/grub-setup.c (setup): Refuse to overwrite XFS superblock.
+       (options): New option --destroy-xfs.
+       (main): Handle --destroy-xfs.
+
+2009-10-16  Vladimir Serbinenko  <address@hidden>
+
        Let user specify OpenBSD root device.
 
        * loader/i386/bsd.c (openbsd_root): New variable.
diff --git a/util/i386/pc/grub-setup.c b/util/i386/pc/grub-setup.c
index ccfbd1d..4ef746b 100644
--- a/util/i386/pc/grub-setup.c
+++ b/util/i386/pc/grub-setup.c
@@ -86,7 +86,8 @@ grub_refresh (void)
 static void
 setup (const char *dir,
        const char *boot_file, const char *core_file,
-       const char *root, const char *dest, int must_embed, int force)
+       const char *root, const char *dest, int must_embed, int force,
+       int destroy_xfs)
 {
   char *boot_path, *core_path, *core_path_dev;
   char *boot_img, *core_img;
@@ -251,6 +252,13 @@ setup (const char *dir,
   if (grub_disk_read (dest_dev->disk, 0, 0, GRUB_DISK_SECTOR_SIZE, tmp_img))
     grub_util_error ("%s", grub_errmsg);
 
+  if (memcmp (tmp_img, "XFSB", 4) == 0)
+    {
+      grub_util_warn ("This install would require destroying XFS.");
+      if (! destroy_xfs)
+       grub_util_error ("If you really want to destroy it use --destroy-xfs.");
+    }
+
   /* Copy the possible DOS BPB.  */
   memcpy (boot_img + GRUB_BOOT_MACHINE_BPB_START,
          tmp_img + GRUB_BOOT_MACHINE_BPB_START,
@@ -556,6 +564,7 @@ static struct option options[] =
     {"device-map", required_argument, 0, 'm'},
     {"root-device", required_argument, 0, 'r'},
     {"force", no_argument, 0, 'f'},
+    {"destroy-xfs", no_argument, 0, 'X'},
     {"help", no_argument, 0, 'h'},
     {"version", no_argument, 0, 'V'},
     {"verbose", no_argument, 0, 'v'},
@@ -580,6 +589,7 @@ DEVICE must be a GRUB device (e.g. ``(hd0,1)'').\n\
   -m, --device-map=FILE   use FILE as the device map [default=%s]\n\
   -r, --root-device=DEV   use DEV as the root device [default=guessed]\n\
   -f, --force             install even if problems are detected\n\
+  --destroy-xfs           install even destroying XFS superblock\n\
   -h, --help              display this message and exit\n\
   -V, --version           print version information and exit\n\
   -v, --verbose           print verbose messages\n\
@@ -614,6 +624,7 @@ main (int argc, char *argv[])
   char *root_dev = 0;
   char *dest_dev;
   int must_embed = 0, force = 0;
+  int destroy_xfs = 0;
 
   progname = "grub-setup";
 
@@ -666,6 +677,10 @@ main (int argc, char *argv[])
            force = 1;
            break;
 
+         case 'X':
+           destroy_xfs = 1;
+           break;
+
          case 'h':
            usage (0);
            break;
@@ -767,7 +782,8 @@ main (int argc, char *argv[])
          setup (dir ? : DEFAULT_DIRECTORY,
                 boot_file ? : DEFAULT_BOOT_FILE,
                 core_file ? : DEFAULT_CORE_FILE,
-                root_dev, grub_util_get_grub_dev (devicelist[i]), 1, force);
+                root_dev, grub_util_get_grub_dev (devicelist[i]), 1, force,
+                destroy_xfs);
        }
     }
   else
@@ -776,7 +792,7 @@ main (int argc, char *argv[])
     setup (dir ? : DEFAULT_DIRECTORY,
           boot_file ? : DEFAULT_BOOT_FILE,
           core_file ? : DEFAULT_CORE_FILE,
-          root_dev, dest_dev, must_embed, force);
+          root_dev, dest_dev, must_embed, force, destroy_xfs);
 
   /* Free resources.  */
   grub_fini_all ();