xfs: verify icount in superblock write

Add a helper predicate to check the inode count for sanity, then use it
in the superblock write verifier to inspect sb_icount.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>

fs/xfs/libxfs/xfs_sb.c

@@ -154,9 +154,10 @@ xfs_validate_sb_write(
 	 * Carry out additional sb summary counter sanity checks when we write
 	 * the superblock.  We skip this in the read validator because there
 	 * could be newer superblocks in the log and if the values are garbage
-	 * we'll recalculate them at the end of log mount.
+	 * even after replay we'll recalculate them at the end of log mount.
 	 */
 	if (sbp->sb_fdblocks > sbp->sb_dblocks ||
+	    !xfs_verify_icount(mp, sbp->sb_icount) ||
 	    sbp->sb_ifree > sbp->sb_icount) {
 		xfs_warn(mp, "SB summary counter sanity check failed");
 		return -EFSCORRUPTED;

fs/xfs/libxfs/xfs_types.c

@@ -171,3 +171,37 @@ xfs_verify_rtbno(
 {
 	return rtbno < mp->m_sb.sb_rblocks;
 }
+
+/* Calculate the range of valid icount values. */
+static void
+xfs_icount_range(
+	struct xfs_mount	*mp,
+	unsigned long long	*min,
+	unsigned long long	*max)
+{
+	unsigned long long	nr_inos = 0;
+	xfs_agnumber_t		agno;
+
+	/* root, rtbitmap, rtsum all live in the first chunk */
+	*min = XFS_INODES_PER_CHUNK;
+
+	for (agno = 0; agno < mp->m_sb.sb_agcount; agno++) {
+		xfs_agino_t	first, last;
+
+		xfs_agino_range(mp, agno, &first, &last);
+		nr_inos += last - first + 1;
+	}
+	*max = nr_inos;
+}
+
+/* Sanity-checking of inode counts. */
+bool
+xfs_verify_icount(
+	struct xfs_mount	*mp,
+	unsigned long long	icount)
+{
+	unsigned long long	min, max;
+
+	xfs_icount_range(mp, &min, &max);
+	return icount >= min && icount <= max;
+}

fs/xfs/libxfs/xfs_types.h

@@ -165,5 +165,6 @@ bool xfs_verify_ino(struct xfs_mount *mp, xfs_ino_t ino);
 bool xfs_internal_inum(struct xfs_mount *mp, xfs_ino_t ino);
 bool xfs_verify_dir_ino(struct xfs_mount *mp, xfs_ino_t ino);
 bool xfs_verify_rtbno(struct xfs_mount *mp, xfs_rtblock_t rtbno);
+bool xfs_verify_icount(struct xfs_mount *mp, unsigned long long icount);
 
 #endif	/* __XFS_TYPES_H__ */