[RFC PATCH] checkpatch: check Fixes for a Cc: stable tag

[Sabrina Dubroca]

I keep forgetting to add a "Cc: stable@xxxxxxxxxx" tag to my
Fixes. Not all fixes deserve one, but it's a good reminder.

Only print a CHECK-level message if one of the Fixes tags belongs to a
commit present in a released kernel. Fixes for stuff that's only in
-next should be fine without the Cc.

Assisted-by: LLM
Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
---
I don't deserve the credit for more than "suggested-by" on this,
I just fed the idea to claude and it produced this. It seems to do
what I wanted, and looks fairly reasonable to me (as someone who
doesn't know Perl).

 scripts/checkpatch.pl | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8a7787d228a6..8f675445ba51 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1292,6 +1292,16 @@ sub git_commit_info {
 	return ($id, $desc);
 }
 
+sub git_commit_in_release {
+	my ($commit) = @_;
+
+	return undef if ((which("git") eq "") || !(-e "$gitroot"));
+
+	`${git_command} describe --contains --match 'v*' --exclude '*-rc*' $commit 2>/dev/null`;
+
+	return $? == 0;
+}
+
 $chk_signoff = 0 if ($file);
 $chk_fixes_tag = 0 if ($file);
 
@@ -2687,6 +2697,8 @@ sub process {
 	my $fixes_tag = 0;
 	my $is_revert = 0;
 	my $needs_fixes_tag = "";
+	my $has_cc_stable = 0;
+	my @old_fixes_without_cc_stable = ();
 	my $author = '';
 	my $authorsignoff = 0;
 	my $author_sob = '';
@@ -3085,6 +3097,11 @@ sub process {
 			my $email = $4;
 			my $ucfirst_sign_off = ucfirst(lc($sign_off));
 
+			if ($sign_off =~ /^cc:$/i &&
+			    $email =~ /stable\@(?:vger\.)?kernel\.org/i) {
+				$has_cc_stable = 1;
+			}
+
 			if ($sign_off !~ /$signature_tags/) {
 				my $suggested_signature = find_standard_signature($sign_off);
 				if ($suggested_signature eq "") {
@@ -3309,6 +3326,15 @@ sub process {
 					$fixed[$fixlinenr] = $fixed;
 				}
 			}
+
+			# Cc: stable@xxxxxxxxxxxxxxx may appear later in the
+			# tags block, so defer the check until the whole
+			# commit log has been scanned.
+			if (defined($cid)) {
+				if (git_commit_in_release($cid)) {
+					push(@old_fixes_without_cc_stable, $herecurr);
+				}
+			}
 		}
 
 # Check email subject for common tools that don't need to be mentioned
@@ -7869,6 +7895,12 @@ sub process {
 			WARN("MISSING_FIXES_TAG",
 				 "The commit message has '$needs_fixes_tag', perhaps it also needs a 'Fixes:' tag?\n");
 		}
+		if (!$has_cc_stable) {
+			foreach my $fixes_herecurr (@old_fixes_without_cc_stable) {
+				CHK("MISSING_FIXES_STABLE_TAG",
+					 "The commit fixed by the Fixes: tag is already present in a released kernel, should the commit have a Cc: stable tag?\n" . $fixes_herecurr);
+			}
+		}
 	}
 	if ($is_patch && $has_commit_log && $chk_signoff) {
 		if ($signoff == 0) {
-- 
2.55.0