ext4: print quota journalling mode on (re-)mount

Right now, it is hard to understand which quota journalling type is enabled:
you need to be quite familiar with kernel code and trace it or really
understand what different combinations of fs flags/mount options lead to.

This patch adds printing of current quota jounalling mode on each
mount/remount, thus making it easier to check it at a glance/in autotests.
The semantics is similar to ext4 data journalling modes:

* journalled - quota configured, journalling will be enabled
* writeback  - quota configured, journalling won't be enabled
* none       - quota isn't configured
* disabled   - kernel compiled without CONFIG_QUOTA feature

Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1603336860-16153-2-git-send-email-dotdot@yandex-team.ru
Signed-off-by: Roman Anufriev <dotdot@yandex-team.ru>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/super.c

@@ -4005,6 +4005,21 @@ static void ext4_set_resv_clusters(struct super_block *sb)
 	atomic64_set(&sbi->s_resv_clusters, resv_clusters);
 }
 
+static const char *ext4_quota_mode(struct super_block *sb)
+{
+#ifdef CONFIG_QUOTA
+	if (!ext4_quota_capable(sb))
+		return "none";
+
+	if (EXT4_SB(sb)->s_journal && ext4_is_quota_journalled(sb))
+		return "journalled";
+	else
+		return "writeback";
+#else
+	return "disabled";
+#endif
+}
+
 static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct dax_device *dax_dev = fs_dax_get_by_bdev(sb->s_bdev);
@@ -5090,10 +5105,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 
 	if (___ratelimit(&ext4_mount_msg_ratelimit, "EXT4-fs mount"))
 		ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
-			 "Opts: %.*s%s%s", descr,
+			 "Opts: %.*s%s%s. Quota mode: %s.", descr,
 			 (int) sizeof(sbi->s_es->s_mount_opts),
 			 sbi->s_es->s_mount_opts,
-			 *sbi->s_es->s_mount_opts ? "; " : "", orig_data);
+			 *sbi->s_es->s_mount_opts ? "; " : "", orig_data,
+			 ext4_quota_mode(sb));
 
 	if (es->s_error_count)
 		mod_timer(&sbi->s_err_report, jiffies + 300*HZ); /* 5 minutes */
@@ -6031,7 +6047,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 	 */
 	*flags = (*flags & ~vfs_flags) | (sb->s_flags & vfs_flags);
 
-	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s", orig_data);
+	ext4_msg(sb, KERN_INFO, "re-mounted. Opts: %s. Quota mode: %s.",
+		 orig_data, ext4_quota_mode(sb));
 	kfree(orig_data);
 	return 0;