checkpatch: improve octal permissions test speed

The current octal permissions test is very slow.

When patch ("checkpatch: add checks for constant non-octal permissions")
was added, processing time approximately tripled.

Regain almost all of the performance by not looping through all the
possible functions unless the line contains one of the functions.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -388,6 +388,13 @@ our @mode_permission_funcs = (
 	["(?:CLASS|DEVICE|SENSOR)_ATTR", 2],
 );
 
+#Create a search pattern for all these functions to speed up a loop below
+our $mode_perms_search = "";
+foreach my $entry (@mode_permission_funcs) {
+	$mode_perms_search .= '|' if ($mode_perms_search ne "");
+	$mode_perms_search .= $entry->[0];
+}
+
 our $allowed_asm_includes = qr{(?x:
 	irq|
 	memory
@@ -4524,26 +4531,30 @@ sub process {
 			     "Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
 		}
 
-		foreach my $entry (@mode_permission_funcs) {
-			my $func = $entry->[0];
-			my $arg_pos = $entry->[1];
-
-			my $skip_args = "";
-			if ($arg_pos > 1) {
-				$arg_pos--;
-				$skip_args = "(?:\\s*$FuncArg\\s*,\\s*){$arg_pos,$arg_pos}";
-			}
-			my $test = "\\b$func\\s*\\(${skip_args}([\\d]+)\\s*[,\\)]";
-			if ($^V && $^V ge 5.10.0 &&
-			    $line =~ /$test/) {
-				my $val = $1;
-				$val = $6 if ($skip_args ne "");
-
-				if ($val !~ /^0$/ &&
-				    (($val =~ /^$Int$/ && $val !~ /^$Octal$/) ||
-				     length($val) ne 4)) {
-					ERROR("NON_OCTAL_PERMISSIONS",
-					      "Use 4 digit octal (0777) not decimal permissions\n" . $herecurr);
+# Mode permission misuses where it seems decimal should be octal
+# This uses a shortcut match to avoid unnecessary uses of a slow foreach loop
+		if ($^V && $^V ge 5.10.0 &&
+		    $line =~ /$mode_perms_search/) {
+			foreach my $entry (@mode_permission_funcs) {
+				my $func = $entry->[0];
+				my $arg_pos = $entry->[1];
+
+				my $skip_args = "";
+				if ($arg_pos > 1) {
+					$arg_pos--;
+					$skip_args = "(?:\\s*$FuncArg\\s*,\\s*){$arg_pos,$arg_pos}";
+				}
+				my $test = "\\b$func\\s*\\(${skip_args}([\\d]+)\\s*[,\\)]";
+				if ($line =~ /$test/) {
+					my $val = $1;
+					$val = $6 if ($skip_args ne "");
+
+					if ($val !~ /^0$/ &&
+					    (($val =~ /^$Int$/ && $val !~ /^$Octal$/) ||
+					     length($val) ne 4)) {
+						ERROR("NON_OCTAL_PERMISSIONS",
+						      "Use 4 digit octal (0777) not decimal permissions\n" . $herecurr);
+					}
 				}
 			}
 		}