HACKATHON: Example interdiff github action

.github/workflows/upstream-commit-check.yml

@@ -35,6 +35,26 @@ jobs:
         with:
           python-version: '3.x'
 
+      - name: Install build dependencies for patchutils
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential autoconf automake libtool gnulib
+
+      - name: Clone and build custom patchutils
+        run: |
+          git clone https://github.com/kerneltoast/patchutils
+          cd patchutils
+          ./bootstrap
+          ./configure
+          make -j$(nproc)
+
+      - name: Download run_interdiff.py
+        run: |
+          curl -sL \
+            https://raw.githubusercontent.com/ctrliq/kernel-src-tree-tools/hackathon-cve-check/run_interdiff.py \
+            -o run_interdiff.py
+          chmod +x run_interdiff.py
+
       - name: Run upstream fixes check
         id: checkkernel
         run: |
@@ -44,6 +64,15 @@ jobs:
             echo "has_findings=true" >> $GITHUB_OUTPUT
           fi
 
+      - name: Run interdiff check
+        id: interdiff
+        run: |
+          python3 run_interdiff.py --repo . --pr_branch "${{ github.head_ref }}" --base_branch "${{ github.base_ref }}" --markdown --interdiff ./patchutils/src/interdiff | tee interdiff_result.txt
+          # Save non-empty results for PR comment
+          if grep -q -v "All backported commits match their upstream counterparts." interdiff_result.txt; then
+            echo "has_differences=true" >> $GITHUB_OUTPUT
+          fi
+
       - name: Comment on PR if issues found
         if: steps.checkkernel.outputs.has_findings == 'true'
         env:
@@ -52,3 +81,12 @@ jobs:
           gh pr comment ${{ github.event.pull_request.number }} \
             --body "$(cat result.txt)" \
             --repo ${{ github.repository }}
+
+      - name: Comment on PR if interdiff differences found
+        if: steps.interdiff.outputs.has_differences == 'true'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh pr comment ${{ github.event.pull_request.number }} \
+            --body "$(cat interdiff_result.txt)" \
+            --repo ${{ github.repository }}

fs/ext4/ext4.h

@@ -1803,7 +1803,8 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 enum {
 	EXT4_MF_MNTDIR_SAMPLED,
 	EXT4_MF_FS_ABORTED,	/* Fatal error detected */
-	EXT4_MF_FC_INELIGIBLE	/* Fast commit ineligible */
+	EXT4_MF_FC_INELIGIBLE,	/* Fast commit ineligible */
+	EXT4_MF_JOURNAL_DESTROY	/* Journal is in process of destroying */
 };
 
 static inline void ext4_set_mount_flag(struct super_block *sb, int bit)

fs/ext4/ext4_jbd2.h

@@ -521,6 +521,21 @@ static inline int ext4_journal_destroy(struct ext4_sb_info *sbi, journal_t *jour
 {
 	int err = 0;
 
+	/*
+	 * At this point only two things can be operating on the journal.
+	 * JBD2 thread performing transaction commit and s_sb_upd_work
+	 * issuing sb update through the journal. Once we set
+	 * EXT4_JOURNAL_DESTROY, new ext4_handle_error() calls will not
+	 * queue s_sb_upd_work and ext4_force_commit() makes sure any
+	 * ext4_handle_error() calls from the running transaction commit are
+	 * finished. Hence no new s_sb_upd_work can be queued after we
+	 * flush it here.
+	 */
+	ext4_set_mount_flag(sbi->s_sb, EXT4_MF_JOURNAL_DESTROY);
+
+	ext4_force_commit(sbi->s_sb);
+	flush_work(&sbi->s_sb_upd_work);
+
 	err = jbd2_journal_destroy(journal);
 	sbi->s_journal = NULL;
 

fs/ext4/super.c

@@ -668,9 +668,13 @@ static void ext4_handle_error(struct super_block *sb, bool force_ro, int error,
 		 * In case the fs should keep running, we need to writeout
 		 * superblock through the journal. Due to lock ordering
 		 * constraints, it may not be safe to do it right here so we
-		 * defer superblock flushing to a workqueue.
+		 * defer superblock flushing to a workqueue. We just need to be
+		 * careful when the journal is already shutting down. If we get
+		 * here in that case, just update the sb directly as the last
+		 * transaction won't commit anyway.
 		 */
-		if (continue_fs && journal)
+		if (continue_fs && journal &&
+		    !ext4_test_mount_flag(sb, EXT4_MF_JOURNAL_DESTROY))
 			schedule_work(&EXT4_SB(sb)->s_sb_upd_work);
 		else
 			ext4_commit_super(sb);
@@ -1203,7 +1207,6 @@ static void ext4_put_super(struct super_block *sb)
 	ext4_unregister_li_request(sb);
 	ext4_quota_off_umount(sb);
 
-	flush_work(&sbi->s_sb_upd_work);
 	destroy_workqueue(sbi->rsv_conversion_wq);
 	ext4_release_orphan_info(sb);
 
@@ -1213,7 +1216,8 @@ static void ext4_put_super(struct super_block *sb)
 		if ((err < 0) && !aborted) {
 			ext4_abort(sb, -err, "Couldn't clean up the journal");
 		}
-	}
+	} else
+		flush_work(&sbi->s_sb_upd_work);
 
 	ext4_es_unregister_shrinker(sbi);
 	del_timer_sync(&sbi->s_err_report);
@@ -4891,8 +4895,6 @@ static int ext4_load_and_init_journal(struct super_block *sb,
 	return 0;
 
 out:
-	/* flush s_sb_upd_work before destroying the journal. */
-	flush_work(&sbi->s_sb_upd_work);
 	ext4_journal_destroy(sbi, sbi->s_journal);
 	return -EINVAL;
 }
@@ -5599,8 +5601,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	sbi->s_ea_block_cache = NULL;
 
 	if (sbi->s_journal) {
-		/* flush s_sb_upd_work before journal destroy. */
-		flush_work(&sbi->s_sb_upd_work);
 		ext4_journal_destroy(sbi, sbi->s_journal);
 	}
 failed_mount3a: