xfs: repair superblocks

If one of the backup superblocks is found to differ seriously from
superblock 0, write out a fresh copy from the in-core sb.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/Makefile

@@ -168,6 +168,7 @@ xfs-$(CONFIG_XFS_QUOTA)		+= scrub/quota.o
 # online repair
 ifeq ($(CONFIG_XFS_ONLINE_REPAIR),y)
 xfs-y				+= $(addprefix scrub/, \
+				   agheader_repair.o \
 				   repair.o \
 				   )
 endif

fs/xfs/libxfs/xfs_sb.c

@@ -1097,3 +1097,25 @@ xfs_sb_read_secondary(
 	*bpp = bp;
 	return 0;
 }
+
+/* Get an uninitialised secondary superblock buffer. */
+int
+xfs_sb_get_secondary(
+	struct xfs_mount	*mp,
+	struct xfs_trans	*tp,
+	xfs_agnumber_t		agno,
+	struct xfs_buf		**bpp)
+{
+	struct xfs_buf		*bp;
+
+	ASSERT(agno != 0 && agno != NULLAGNUMBER);
+	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
+			XFS_AG_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
+			XFS_FSS_TO_BB(mp, 1), 0);
+	if (!bp)
+		return -ENOMEM;
+	bp->b_ops = &xfs_sb_buf_ops;
+	xfs_buf_oneshot(bp);
+	*bpp = bp;
+	return 0;
+}

fs/xfs/libxfs/xfs_sb.h

@@ -50,5 +50,8 @@ extern int	xfs_fs_geometry(struct xfs_sb *sbp, struct xfs_fsop_geom *geo,
 extern int	xfs_sb_read_secondary(struct xfs_mount *mp,
 				struct xfs_trans *tp, xfs_agnumber_t agno,
 				struct xfs_buf **bpp);
+extern int	xfs_sb_get_secondary(struct xfs_mount *mp,
+				struct xfs_trans *tp, xfs_agnumber_t agno,
+				struct xfs_buf **bpp);
 
 #endif	/* __XFS_SB_H__ */

fs/xfs/scrub/agheader_repair.c

@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2018 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_alloc.h"
+#include "xfs_ialloc.h"
+#include "xfs_rmap.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+
+/* Superblock */
+
+/* Repair the superblock. */
+int
+xfs_repair_superblock(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_mount		*mp = sc->mp;
+	struct xfs_buf			*bp;
+	xfs_agnumber_t			agno;
+	int				error;
+
+	/* Don't try to repair AG 0's sb; let xfs_repair deal with it. */
+	agno = sc->sm->sm_agno;
+	if (agno == 0)
+		return -EOPNOTSUPP;
+
+	error = xfs_sb_get_secondary(mp, sc->tp, agno, &bp);
+	if (error)
+		return error;
+
+	/* Copy AG 0's superblock to this one. */
+	xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
+	xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb);
+
+	/* Write this to disk. */
+	xfs_trans_buf_set_type(sc->tp, bp, XFS_BLFT_SB_BUF);
+	xfs_trans_log_buf(sc->tp, bp, 0, BBTOB(bp->b_length) - 1);
+	return error;
+}

fs/xfs/scrub/repair.h

@@ -102,6 +102,7 @@ int xfs_repair_ino_dqattach(struct xfs_scrub_context *sc);
 /* Metadata repairers */
 
 int xfs_repair_probe(struct xfs_scrub_context *sc);
+int xfs_repair_superblock(struct xfs_scrub_context *sc);
 
 #else
 
@@ -124,6 +125,7 @@ xfs_repair_calc_ag_resblks(
 }
 
 #define xfs_repair_probe		xfs_repair_notsupported
+#define xfs_repair_superblock		xfs_repair_notsupported
 
 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 

fs/xfs/scrub/scrub.c

@@ -216,7 +216,7 @@ static const struct xfs_scrub_meta_ops meta_scrub_ops[] = {
 		.type	= ST_PERAG,
 		.setup	= xfs_scrub_setup_fs,
 		.scrub	= xfs_scrub_superblock,
-		.repair	= xfs_repair_notsupported,
+		.repair	= xfs_repair_superblock,
 	},
 	[XFS_SCRUB_TYPE_AGF] = {	/* agf */
 		.type	= ST_PERAG,