xfs_repair: try to correct sb_unit value from secondaries

If the primary superblock's sb_unit leads to a rootino calculation that
doesn't match sb_rootino /but/ we can find a secondary superblock whose
sb_unit does match, fix the primary.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/libxfs/libxfs_api_defs.h b/libxfs/libxfs_api_defs.h
index 7c629c625f078b8805a2dd9bfbf3fa05a66bed0a..1a438e5867b5fa517c53c8ba7e4e5c7b3e21a74d 100644 (file)
--- a/libxfs/libxfs_api_defs.h
+++ b/libxfs/libxfs_api_defs.h
@@ -143,6 +143,7 @@
 #define xfs_rtfree_extent              libxfs_rtfree_extent
 #define xfs_sb_from_disk               libxfs_sb_from_disk
 #define xfs_sb_quota_from_disk         libxfs_sb_quota_from_disk
+#define xfs_sb_read_secondary          libxfs_sb_read_secondary
 #define xfs_sb_to_disk                 libxfs_sb_to_disk
 #define xfs_symlink_blocks             libxfs_symlink_blocks
 #define xfs_symlink_hdr_ok             libxfs_symlink_hdr_ok

diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index b34d41d48ad764e7f7a91dca989b0c38d2d8c380..eb1ce5460d3825aaec0cd4613b8daa552da79bf2 100644 (file)
--- a/repair/xfs_repair.c
+++ b/repair/xfs_repair.c
@@ -457,6 +457,84 @@ out:
        return ret;
 }
 
+/*
+ * If any of the secondary SBs contain a *correct* value for sunit, write that
+ * back to the primary superblock.
+ */
+static void
+guess_correct_sunit(
+       struct xfs_mount        *mp)
+{
+       struct xfs_sb           sb;
+       struct xfs_buf          *bp;
+       xfs_ino_t               calc_rootino = NULLFSINO;
+       xfs_agnumber_t          agno;
+       unsigned int            new_sunit;
+       unsigned int            sunit_guess;
+       int                     error;
+
+       /* Try reading secondary supers to see if we find a good sb_unit. */
+       for (agno = 1; agno < mp->m_sb.sb_agcount; agno++) {
+               error = -libxfs_sb_read_secondary(mp, NULL, agno, &bp);
+               if (error)
+                       continue;
+               libxfs_sb_from_disk(&sb, XFS_BUF_TO_SBP(bp));
+               libxfs_putbuf(bp);
+
+               calc_rootino = libxfs_ialloc_calc_rootino(mp, sb.sb_unit);
+               if (calc_rootino == mp->m_sb.sb_rootino)
+                       break;
+       }
+
+       /* If we found a reasonable value, log where we found it. */
+       if (calc_rootino == mp->m_sb.sb_rootino) {
+               do_warn(_("AG %u superblock contains plausible sb_unit value\n"),
+                               agno);
+               new_sunit = sb.sb_unit;
+               goto fix;
+       }
+
+       /* Try successive powers of two. */
+       for (sunit_guess = 1;
+            sunit_guess <= XFS_AG_MAX_BLOCKS(mp->m_sb.sb_blocklog);
+            sunit_guess *= 2) {
+               calc_rootino = libxfs_ialloc_calc_rootino(mp, sunit_guess);
+               if (calc_rootino == mp->m_sb.sb_rootino)
+                       break;
+       }
+
+       /* If we found a reasonable value, log where we found it. */
+       if (calc_rootino == mp->m_sb.sb_rootino) {
+               do_warn(_("Found an sb_unit value that looks plausible\n"));
+               new_sunit = sunit_guess;
+               goto fix;
+       }
+
+       do_warn(_("Could not estimate a plausible sb_unit value\n"));
+       return;
+
+fix:
+       if (!no_modify)
+               do_warn(_("Resetting sb_unit to %u\n"), new_sunit);
+       else
+               do_warn(_("Would reset sb_unit to %u\n"), new_sunit);
+
+       /*
+        * Just set the value -- safe since the superblock doesn't get flushed
+        * out if no_modify is set.
+        */
+       mp->m_sb.sb_unit = new_sunit;
+
+       /* Make sure that swidth is still a multiple of sunit. */
+       if (mp->m_sb.sb_width % mp->m_sb.sb_unit == 0)
+               return;
+
+       if (!no_modify)
+               do_warn(_("Resetting sb_width to %u\n"), new_sunit);
+       else
+               do_warn(_("Would reset sb_width to %u\n"), new_sunit);
+}
+
 /*
  * Make sure that the first 3 inodes in the filesystem are the root directory,
  * the realtime bitmap, and the realtime summary, in that order.
@@ -480,6 +558,7 @@ calc_mkfs(
                do_warn(
 _("sb root inode value %" PRIu64 " valid but in unaligned location (expected %"PRIu64") possibly due to sunit change\n"),
                        mp->m_sb.sb_rootino, rootino);
+               guess_correct_sunit(mp);
                rootino = mp->m_sb.sb_rootino;
        }