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[PATCH, RFC] xfs_repair: allow filesystems with a single AG

To: Arkadiusz Miskiewicz <arekm@xxxxxxxx>
Subject: [PATCH, RFC] xfs_repair: allow filesystems with a single AG
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Wed, 24 Dec 2008 18:19:01 -0500
Cc: xfs@xxxxxxxxxxx
User-agent: Mutt/1.5.18 (2008-05-17)
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.

Skip the geomery validation because we simply can't do it if we don't
have a secondary SB, and make sure to take the internal log into account
when guestimating the first inode cluster.

I'll also cook up a testcase for repair on single AG filesystems.


Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reported-By: Arkadiusz Miskiewicz <arekm@xxxxxxxx>

Index: xfsprogs/repair/sb.c
===================================================================
--- xfsprogs.orig/repair/sb.c   2008-12-24 23:36:29.946033933 +0100
+++ xfsprogs/repair/sb.c        2008-12-24 23:42:08.101044710 +0100
@@ -773,14 +773,17 @@ verify_set_primary_sb(xfs_sb_t            *rsb,
                break;
        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.  Not much we can do here, as we don't want
+                * to prevent the user from checking the filesystem.
+                *
+                * XXX(hch): We should allow putting a secondary superblock
+                *           into the last sector of a filesystem to so that
+                *           we can still have a backup for single allocation
+                *           group filesystems.
                 */
-               if (!force_geo)  {
-                       do_warn(_("Only one AG detected - cannot proceed.\n"));
-                       exit(1);
-               }
+               break;
        default:
                /*
                 * at least half of the probed superblocks have
Index: xfsprogs/repair/xfs_repair.c
===================================================================
--- xfsprogs.orig/repair/xfs_repair.c   2008-12-25 00:00:09.116033372 +0100
+++ xfsprogs/repair/xfs_repair.c        2008-12-25 00:07:50.295036179 +0100
@@ -409,6 +409,19 @@ 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)  {

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