xfs: check the realtime superblock at mount time

Check the realtime superblock at mount time, to ensure that the label
and uuids actually match the primary superblock on the data device.  If
the rt superblock is good, attach it to the xfs_mount so that the log
can use ordered buffers to keep this primary in sync with the primary
super on the data device.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 50 insertions, 0 deletions

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index b4687a8759b1..abeedc848b3b 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -1152,6 +1152,56 @@ out_unlock:
 	return error;
 }
 
+/* Read the realtime superblock and attach it to the mount. */
+int
+xfs_rtmount_readsb(
+	struct xfs_mount	*mp)
+{
+	struct xfs_buf		*bp;
+	int			error;
+
+	if (!xfs_has_rtsb(mp))
+		return 0;
+	if (mp->m_sb.sb_rblocks == 0)
+		return 0;
+	if (mp->m_rtdev_targp == NULL) {
+		xfs_warn(mp,
+	"Filesystem has a realtime volume, use rtdev=device option");
+		return -ENODEV;
+	}
+
+	/* m_blkbb_log is not set up yet */
+	error = xfs_buf_read_uncached(mp->m_rtdev_targp, XFS_RTSB_DADDR,
+			mp->m_sb.sb_blocksize >> BBSHIFT, XBF_NO_IOACCT, &bp,
+			&xfs_rtsb_buf_ops);
+	if (error) {
+		xfs_warn(mp, "rt sb validate failed with error %d.", error);
+		/* bad CRC means corrupted metadata */
+		if (error == -EFSBADCRC)
+			error = -EFSCORRUPTED;
+		return error;
+	}
+
+	mp->m_rtsb_bp = bp;
+	xfs_buf_unlock(bp);
+	return 0;
+}
+
+/* Detach the realtime superblock from the mount and free it. */
+void
+xfs_rtmount_freesb(
+	struct xfs_mount	*mp)
+{
+	struct xfs_buf		*bp = mp->m_rtsb_bp;
+
+	if (!bp)
+		return;
+
+	xfs_buf_lock(bp);
+	mp->m_rtsb_bp = NULL;
+	xfs_buf_relse(bp);
+}
+
 /*
  * Initialize realtime fields in the mount structure.
  */