[PATCH v4 03/18] btrfs: expose quota mode via sysfs

[Boris Burkov <boris@bur.io>]

Add a new sysfs file
/sys/fs/btrfs/<uuid>/qgroups/mode
which prints out the mode qgroups is running in. The possible modes are
disabled, qgroup, and squota

Signed-off-by: Boris Burkov <boris@bur.io>
---
 fs/btrfs/sysfs.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index b1d1ac25237b..e53614753391 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -2086,6 +2086,31 @@ static ssize_t qgroup_enabled_show(struct kobject *qgroups_kobj,
 }
 BTRFS_ATTR(qgroups, enabled, qgroup_enabled_show);
 
+static ssize_t qgroup_mode_show(struct kobject *qgroups_kobj,
+				struct kobj_attribute *a,
+				char *buf)
+{
+	struct btrfs_fs_info *fs_info = to_fs_info(qgroups_kobj->parent);
+	char *mode = "";
+
+	spin_lock(&fs_info->qgroup_lock);
+	switch (btrfs_qgroup_mode(fs_info)) {
+	case BTRFS_QGROUP_MODE_DISABLED:
+		mode = "disabled";
+		break;
+	case BTRFS_QGROUP_MODE_FULL:
+		mode = "qgroup";
+		break;
+	case BTRFS_QGROUP_MODE_SIMPLE:
+		mode = "squota";
+		break;
+	}
+	spin_unlock(&fs_info->qgroup_lock);
+
+	return sysfs_emit(buf, "%s\n", mode);
+}
+BTRFS_ATTR(qgroups, mode, qgroup_mode_show);
+
 static ssize_t qgroup_inconsistent_show(struct kobject *qgroups_kobj,
 					struct kobj_attribute *a,
 					char *buf)
@@ -2148,6 +2173,7 @@ static struct attribute *qgroups_attrs[] = {
 	BTRFS_ATTR_PTR(qgroups, enabled),
 	BTRFS_ATTR_PTR(qgroups, inconsistent),
 	BTRFS_ATTR_PTR(qgroups, drop_subtree_threshold),
+	BTRFS_ATTR_PTR(qgroups, mode),
 	NULL
 };
 ATTRIBUTE_GROUPS(qgroups);
-- 
2.41.0