[PATCH] xfs_repair: allow filesystems with a single allocation group

[Christoph Hellwig]

Lachlan, Eric,

does this version look okay now?

On Mon, Jan 05, 2009 at 03:19:42PM -0500, Christoph Hellwig wrote:
> Currently xfs_repair bails out on a filesystem with just a single AG.
> But that's a perfectly valid configureation, so we should allow it.
> 
> Because we could cause harm only allow it when using the force_geometry
> suboption.  But we nice enough to tell the user about it when he needs it.
> 
> Also make sure to take the internal log into account when guestimating the
> first inode cluster offset.
> 
> I'll also cook up a testcase for repair on single AG filesystems.
> 
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> Reported-By: Arkadiusz Miskiewicz <arekm at maven.pl>
> 
> Index: xfsprogs-dev/repair/sb.c
> ===================================================================
> --- xfsprogs-dev.orig/repair/sb.c	2009-01-03 21:57:42.415546683 +0100
> +++ xfsprogs-dev/repair/sb.c	2009-01-05 21:19:01.706752325 +0100
> @@ -760,27 +760,37 @@ verify_set_primary_sb(xfs_sb_t		*rsb,
>  	switch (num_sbs)  {
>  	case 2:
>  		/*
> -		 * all them have to be right.  if not, report geometry
> -		 * and get out unless force option is in effect (-F)
> +		 * If we only have two allocation groups, and the superblock
> +		 * in the second allocation group differs from the primary
> +		 * superblock we can't verify the geometry information.
> +		 * Warn the user about this situation and get out unless
> +		 * explicitly overridden.
>  		 */
>  		if (current->refs != 2)  {
>  			if (!force_geo)  {
>  				do_warn(
> -	_("Only two AGs detected and they do not match - cannot proceed.\n"));
> +	_("Only two AGs detected and they do not match - "
> +	  "cannot validate filesystem geometry.\n"
> +	  "Use the -o force_geometry option to proceed.\n"));
>  				exit(1);
>  			}
>  		}
> -		break;
> +		goto out_free_list;
>  	case 1:
>  		/*
> -		 * just report the geometry info and get out.
> -		 * refuse to run further unless the force (-F)
> -		 * option is in effect.
> +		 * If we only have a single allocation group there is no
> +		 * secondary superblock that we can use to verify the geometry
> +		 * information.  Warn the user about this situation and get
> +		 * out unless explicitly overridden.
>  		 */
>  		if (!force_geo)  {
> -			do_warn(_("Only one AG detected - cannot proceed.\n"));
> +			do_warn(
> +	_("Only one AG detected - "
> +	  "cannot validate filesystem geometry.\n"
> +	  "Use the -o force_geometry option to proceed.\n"));
>  			exit(1);
>  		}
> +		goto out_free_list;
>  	default:
>  		/*
>  		 * at least half of the probed superblocks have
> @@ -820,6 +830,7 @@ verify_set_primary_sb(xfs_sb_t		*rsb,
>  		sb_width = sb->sb_width;
>  	}
>  
> +out_free_list:
>  	free_geo(list);
>  out:
>  	free(sb);
> Index: xfsprogs-dev/repair/xfs_repair.c
> ===================================================================
> --- xfsprogs-dev.orig/repair/xfs_repair.c	2009-01-03 21:57:42.416547229 +0100
> +++ xfsprogs-dev/repair/xfs_repair.c	2009-01-05 20:53:24.810738262 +0100
> @@ -62,6 +62,8 @@ char *o_opts[] = {
>  	"bhash",
>  #define	AG_STRIDE	4
>  	"ag_stride",
> +#define FORCE_GEO	5
> +	"force_geometry",
>  	NULL
>  };
>  
> @@ -258,6 +260,13 @@ process_args(int argc, char **argv)
>  				case AG_STRIDE:
>  					ag_stride = (int)strtol(val, NULL, 0);
>  					break;
> +				case FORCE_GEO:
> +					if (val)
> +						noval('o', o_opts, FORCE_GEO);
> +					if (force_geo)
> +						respec('o', o_opts, FORCE_GEO);
> +					force_geo = 1;
> +					break;
>  				default:
>  					unknown('o', val);
>  					break;
> @@ -409,6 +418,19 @@ calc_mkfs(xfs_mount_t *mp)
>  	fino_bno = inobt_root + XFS_MIN_FREELIST_RAW(1, 1, mp) + 1;
>  
>  	/*
> +	 * If we only have a single allocation group the log is also allocated
> +	 * in the first allocation group and we need to add the number of
> +	 * blocks used by the log to the above calculation.
> +	 * All this of course doesn't apply if we have an external log.
> +	 */
> +	if (mp->m_sb.sb_agcount == 1 && mp->m_sb.sb_logstart) {
> +		/*
> +		 * XXX(hch): verify that sb_logstart makes sense?
> +		 */
> +		 fino_bno += mp->m_sb.sb_logblocks;
> +	}
> +
> +	/*
>  	 * ditto the location of the first inode chunks in the fs ('/')
>  	 */
>  	if (xfs_sb_version_hasdalign(&mp->m_sb) && do_inoalign)  {
> Index: xfsprogs-dev/man/man8/xfs_repair.8
> ===================================================================
> --- xfsprogs-dev.orig/man/man8/xfs_repair.8	2009-01-05 21:11:50.054546919 +0100
> +++ xfsprogs-dev/man/man8/xfs_repair.8	2009-01-05 21:14:49.228027165 +0100
> @@ -146,6 +146,15 @@ RAM size.
>  This creates additional processing threads to parallel process
>  AGs that span multiple concat units. This can significantly
>  reduce repair times on concat based filesystems.
> +.TP
> +.BI force_geometry
> +Check the filesystem even if geometry information could not be validate.
> +Geometry information can not be validated if there is only a single
> +allocation group exists and thus no backups superblock exists, or
> +if there are two allocation groups and the two superblocks do not
> +agree on the filesystem geometry.  Only use this option if you validated
> +the geometry yourself and know what your doing.  In doubt do a run
> +in no modify mode first.
>  .RE
>  .TP
>  .B \-t " interval"
> 
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> http://oss.sgi.com/mailman/listinfo/xfs
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