xfs: report proper f_files in statfs if we overshoot imaxpct

Normally, a statfs syscall reports m_maxicount as f_files
(total file nodes in file system) because it is supposed
to be the upper limit for dynamically-allocated inodes.

It's possible, however, to overshoot imaxpct / m_maxicount.
If this happens, we should report the actual number of allocated
inodes, which is contained in sb_icount.  Add one more adjustment
to the statfs code to make this happen.

Reported-by: Alexander Tsvetkov <alexander.tsvetkov@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_super.c

@@ -1111,6 +1111,11 @@ xfs_fs_statfs(
 					statp->f_files,
 					mp->m_maxicount);
 
+	/* If sb_icount overshot maxicount, report actual allocation */
+	statp->f_files = max_t(typeof(statp->f_files),
+					statp->f_files,
+					sbp->sb_icount);
+
 	/* make sure statp->f_ffree does not underflow */
 	ffree = statp->f_files - (sbp->sb_icount - sbp->sb_ifree);
 	statp->f_ffree = max_t(__int64_t, ffree, 0);