checkpatch: trailing statements ensure we report the end of the line

When reporting some complex trailing statements we report only the
starting line of the error, that tends to imply the shown line is in error
and confuse the reader.  As we do know where the actual error is report
that line too with an appropriate gap marker where applicable.

    #ERROR: trailing statements should be on next line
    #1: FILE: Z202.c:1:
    +       for (pbh = page_buffers(bh->b_page); pbh != bh;
    +               pbh = pbh->b_this_page, key++);
    #ERROR: trailing statements should be on next line
    #4: FILE: Z202.c:4:
    +       for (pbh = page_buffers(bh->b_page);
    [...]
    +               pbh = pbh->b_this_page, key++);
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2001,7 +2001,16 @@ sub process {
 			if (length($c) && $s !~ /^\s*{?\s*\\*\s*$/ &&
 			    $c !~ /}\s*while\s*/)
 			{
-				ERROR("trailing statements should be on next line\n" . $herecurr);
+				# Find out how long the conditional actually is.
+				my @newlines = ($c =~ /\n/gs);
+				my $cond_lines = 1 + $#newlines;
+
+				my $stat_real = raw_line($linenr, $cond_lines);
+				if (defined($stat_real) && $cond_lines > 1) {
+					$stat_real = "[...]\n$stat_real";
+				}
+
+				ERROR("trailing statements should be on next line\n" . $herecurr . $stat_real);
 			}
 		}