xfs: update superblock counters correctly for !lazysbcount

Keep the mount superblock counters up to date for !lazysbcount
filesystems so that when we log the superblock they do not need
updating in any way because they are already correct.

It's found by what Zorro reported:
1. mkfs.xfs -f -l lazy-count=0 -m crc=0 $dev
2. mount $dev $mnt
3. fsstress -d $mnt -p 100 -n 1000 (maybe need more or less io load)
4. umount $mnt
5. xfs_repair -n $dev
and I've seen no problem with this patch.

Signed-off-by: Dave Chinner <[email protected]>
Reported-by: Zorro Lang <[email protected]>
Reviewed-by: Gao Xiang <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Brian Foster <[email protected]>

Author: Dave Chinner

fs/xfs/libxfs/xfs_sb.c

@@ -926,9 +926,19 @@ xfs_log_sb(
 	struct xfs_mount	*mp = tp->t_mountp;
 	struct xfs_buf		*bp = xfs_trans_getsb(tp);
 
-	mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount);
-	mp->m_sb.sb_ifree = percpu_counter_sum(&mp->m_ifree);
-	mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+	/*
+	 * Lazy sb counters don't update the in-core superblock so do that now.
+	 * If this is at unmount, the counters will be exactly correct, but at
+	 * any other time they will only be ballpark correct because of
+	 * reservations that have been taken out percpu counters. If we have an
+	 * unclean shutdown, this will be corrected by log recovery rebuilding
+	 * the counters from the AGF block counts.
+	 */
+	if (xfs_sb_version_haslazysbcount(&mp->m_sb)) {
+		mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount);
+		mp->m_sb.sb_ifree = percpu_counter_sum(&mp->m_ifree);
+		mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+	}
 
 	xfs_sb_to_disk(bp->b_addr, &mp->m_sb);
 	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);

fs/xfs/xfs_trans.c

@@ -622,6 +622,9 @@ xfs_trans_unreserve_and_mod_sb(
 
 	/* apply remaining deltas */
 	spin_lock(&mp->m_sb_lock);
+	mp->m_sb.sb_fdblocks += tp->t_fdblocks_delta + tp->t_res_fdblocks_delta;
+	mp->m_sb.sb_icount += idelta;
+	mp->m_sb.sb_ifree += ifreedelta;
 	mp->m_sb.sb_frextents += rtxdelta;
 	mp->m_sb.sb_dblocks += tp->t_dblocks_delta;
 	mp->m_sb.sb_agcount += tp->t_agcount_delta;