e2fsck: Detect unordered extents in an extent node

The logical block numbers must be monotonically increasing, and there
must not be any overlapping extents.  If any are found, report them as
filesystem corruption.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/e2fsck/problem.c b/e2fsck/problem.c
index d9ae911..81ad9b0 100644
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -849,6 +849,11 @@
 	  N_("Fast symlink %i has EXTENT_FL set.  "),
 	  PROMPT_CLEAR, 0 },
 
+	/* Extents are out of order */
+	{ PR_1_OUT_OF_ORDER_EXTENTS,
+	  N_("@i %i has out of order extents\n\t(@n logical @b %c, physical @b %b, len %N)\n"),
+	  PROMPT_CLEAR, 0 },
+
 	/* Pass 1b errors */
 
 	/* Pass 1B: Rescan for duplicate/bad blocks */