ext4: Record error messages in super block

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cc5c157..056da19 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -326,10 +326,52 @@  int __ext4_journal_stop(const char *where, unsigned int line, handle_t *handle)
 	return err;
 }
 
+/* record error messages after journal super block */
+static void ext4_record_journal_err(struct super_block *sb, const char *where,
+		const char *function, const char *fmt, va_list args)
+{
+#define MSGLEN 256
+	journal_t *journal = EXT4_SB(sb)->s_journal;
+	char *buf;
+	unsigned long offset;
+	int len;
+	if (!journal)
+		return;
+
+	buf = (char *)journal->j_superblock;
+	offset = (unsigned long)buf % sb->s_blocksize;
+	buf += sizeof(journal_superblock_t);
+	offset += sizeof(journal_superblock_t);
+
+	/* seek to end of message buffer */
+	while (offset < sb->s_blocksize && *buf) {
+		buf += MSGLEN;
+		offset += MSGLEN;
+	}
+
+	if (offset+MSGLEN > sb->s_blocksize)
+		/* no space left in message buffer */
+		return;
+
+	len = snprintf(buf, MSGLEN, "%s: %s: ", where, function);
+	len += vsnprintf(buf + len, MSGLEN - len, fmt, args);
+}
+
+static void ext4_record_journal_errstr(struct super_block *sb,
+		const char *where, const char *function, ...)
+{
+	va_list args;
+
+	va_start(args, function);
+	ext4_record_journal_err(sb, where, function, "%s\n", args);
+	va_end(args);
+}
+
 void ext4_journal_abort_handle(const char *caller, unsigned int line,
 			       const char *err_fn, struct buffer_head *bh,
 			       handle_t *handle, int err)
 {
+	struct super_block *sb = handle->h_transaction->t_journal->j_private;
 	char nbuf[16];
 	const char *errstr = ext4_decode_error(NULL, err, nbuf);
 
@@ -347,6 +389,8 @@  void ext4_journal_abort_handle(const char *caller, unsigned int line,
 	printk(KERN_ERR "%s:%d: aborting transaction: %s in %s\n",
 	       caller, line, errstr, err_fn);
 
+	/* record error message in journal super block */
+	ext4_record_journal_errstr(sb, caller, err_fn, errstr);
 	jbd2_journal_abort_handle(handle);
 }
 
@@ -434,6 +478,11 @@  void __ext4_error(struct super_block *sb, const char *function,
 	       sb->s_id, function, line, current->comm, &vaf);
 	va_end(args);
 
+	/* record error message in journal super block */
+	va_start(args, fmt);
+	ext4_record_journal_err(sb, __func__, function, fmt, args);
+	va_end(args);
+
 	ext4_handle_error(sb);
 }
 
@@ -458,6 +507,11 @@  void ext4_error_inode(struct inode *inode, const char *function,
 	printk(KERN_CONT "comm %s: %pV\n", current->comm, &vaf);
 	va_end(args);
 
+	/* record error message in journal super block */
+	va_start(args, fmt);
+	ext4_record_journal_err(inode->i_sb, __func__, function, fmt, args);
+	va_end(args);
+
 	ext4_handle_error(inode->i_sb);
 }
 
@@ -488,6 +542,11 @@  void ext4_error_file(struct file *file, const char *function,
 	printk(KERN_CONT "comm %s: path %s: %pV\n", current->comm, path, &vaf);
 	va_end(args);
 
+	/* record error message in journal super block */
+	va_start(args, fmt);
+	ext4_record_journal_err(inode->i_sb, __func__, function, fmt, args);
+	va_end(args);
+
 	ext4_handle_error(inode->i_sb);
 }
 
@@ -546,6 +605,9 @@  void __ext4_std_error(struct super_block *sb, const char *function,
 	       sb->s_id, function, line, errstr);
 	save_error_info(sb, function, line);
 
+	/* record error message in journal super block */
+	ext4_record_journal_errstr(sb, __func__, function, errstr);
+
 	ext4_handle_error(sb);
 }
 
@@ -572,6 +634,11 @@  void __ext4_abort(struct super_block *sb, const char *function,
 	printk("\n");
 	va_end(args);
 
+	/* record error message in journal super block */
+	va_start(args, fmt);
+	ext4_record_journal_err(sb, __func__, function, fmt, args);
+	va_end(args);
+
 	if ((sb->s_flags & MS_RDONLY) == 0) {
 		ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
 		sb->s_flags |= MS_RDONLY;
@@ -638,6 +705,11 @@  __acquires(bitlock)
 	printk(KERN_CONT "%pV\n", &vaf);
 	va_end(args);
 
+	/* record error message in journal super block */
+	va_start(args, fmt);
+	ext4_record_journal_err(sb, __func__, function, fmt, args);
+	va_end(args);
+
 	if (test_opt(sb, ERRORS_CONT)) {
 		ext4_commit_super(sb, 0);
 		return;
@@ -4141,11 +4213,34 @@  static void ext4_clear_journal_err(struct super_block *sb,
 	if (j_errno) {
 		char nbuf[16];
 
+		char *buf1, *buf2;
+		unsigned long offset1, offset2;
+		int len1, len2;
+
+		/* copy message buffer from journal to super block */
+		buf1 = (char *)journal->j_superblock;
+		offset1 = (unsigned long)buf1 % sb->s_blocksize;
+		buf1 += sizeof(journal_superblock_t);
+		offset1 += sizeof(journal_superblock_t);
+		len1 = sb->s_blocksize - offset1;
+		buf2 = (char *)EXT4_SB(sb)->s_es;
+		offset2 = (unsigned long)buf2 % sb->s_blocksize;
+		buf2 += sizeof(struct ext4_super_block);
+		offset2 += sizeof(struct ext4_super_block);
+		len2 = sb->s_blocksize - offset2;
+		if (len2 > len1)
+			len2 = len1;
+		if (len2 > 0 && *buf1)
+			memcpy(buf2, buf1, len2);
 		errstr = ext4_decode_error(sb, j_errno, nbuf);
 		ext4_warning(sb, "Filesystem error recorded "
 			     "from previous mount: %s", errstr);
 		ext4_warning(sb, "Marking fs in need of filesystem check.");
 
+		/* clear journal message buffer */
+		if (len1 > 0)
+			memset(buf1, 0, len1);
+
 		EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
 		es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
 		ext4_commit_super(sb, 1);