jbd2: If a journal checksum error is detected, propagate the error to ext4

If a journal checksum error is detected, the ext4 filesystem will call
ext4_error(), and the mount will either continue, become a read-only
mount, or cause a kernel panic based on the superblock flags
indicating the user's preference of what to do in case of filesystem
corruption being detected.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/super.c

@@ -2189,6 +2189,29 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
 	    EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
 		if (ext4_load_journal(sb, es, journal_devnum))
 			goto failed_mount3;
+		if (!(sb->s_flags & MS_RDONLY) &&
+		    EXT4_SB(sb)->s_journal->j_failed_commit) {
+			printk(KERN_CRIT "EXT4-fs error (device %s): "
+			       "ext4_fill_super: Journal transaction "
+			       "%u is corrupt\n", sb->s_id, 
+			       EXT4_SB(sb)->s_journal->j_failed_commit);
+			if (test_opt (sb, ERRORS_RO)) {
+				printk (KERN_CRIT
+					"Mounting filesystem read-only\n");
+				sb->s_flags |= MS_RDONLY;
+				EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
+				es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
+			}
+			if (test_opt(sb, ERRORS_PANIC)) {
+				EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
+				es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
+				ext4_commit_super(sb, es, 1);
+				printk(KERN_CRIT
+				       "EXT4-fs (device %s): mount failed\n",
+				      sb->s_id);
+				goto failed_mount4;
+			}
+		}
 	} else if (journal_inum) {
 		if (ext4_create_journal(sb, es, journal_inum))
 			goto failed_mount3;

fs/jbd2/recovery.c

@@ -611,9 +611,8 @@ static int do_one_pass(journal_t *journal,
 				chksum_err = chksum_seen = 0;
 
 				if (info->end_transaction) {
-					printk(KERN_ERR "JBD: Transaction %u "
-						"found to be corrupt.\n",
-						next_commit_ID - 1);
+					journal->j_failed_commit =
+						info->end_transaction;
 					brelse(bh);
 					break;
 				}
@@ -644,10 +643,8 @@ static int do_one_pass(journal_t *journal,
 
 					if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 					   JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
-						printk(KERN_ERR
-						       "JBD: Transaction %u "
-						       "found to be corrupt.\n",
-						       next_commit_ID);
+						journal->j_failed_commit =
+							next_commit_ID;
 						brelse(bh);
 						break;
 					}

include/linux/jbd2.h

@@ -919,6 +919,9 @@ struct journal_s
 	struct proc_dir_entry	*j_proc_entry;
 	struct transaction_stats_s j_stats;
 
+	/* Failed journal commit ID */
+	unsigned int		j_failed_commit;
+
 	/*
 	 * An opaque pointer to fs-private information.  ext3 puts its
 	 * superblock pointer here