btrfs: qgroup: export qgroups in sysfs

This patch will add the following sysfs interface:

  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/referenced
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/exclusive
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/max_referenced
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/max_exclusive
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/limit_flags

Which is also available in output of "btrfs qgroup show".

  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/rsv_data
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/rsv_meta_pertrans
  /sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/rsv_meta_prealloc

The last 3 rsv related members are not visible to users, but can be very
useful to debug qgroup limit related bugs.

Also, to avoid '/' used in <qgroup_id>, the separator between qgroup
level and qgroup id is changed to '_'.

The interface is not hidden behind 'debug' as we want this interface to
be included into production build and to provide another way to read the
qgroup information besides the ioctls.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 148 insertions, 0 deletions

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index a39bff64ff24..5885abe57c3e 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -19,6 +19,7 @@
 #include "volumes.h"
 #include "space-info.h"
 #include "block-group.h"
+#include "qgroup.h"
 
 struct btrfs_feature_attr {
 	struct kobj_attribute kobj_attr;
@@ -1455,6 +1456,153 @@ failure:
 	return error;
 }
 
+static inline struct btrfs_fs_info *qgroup_kobj_to_fs_info(struct kobject *kobj)
+{
+	return to_fs_info(kobj->parent->parent);
+}
+
+#define QGROUP_ATTR(_member, _show_name)					\
+static ssize_t btrfs_qgroup_show_##_member(struct kobject *qgroup_kobj,		\
+					   struct kobj_attribute *a,		\
+					   char *buf)				\
+{										\
+	struct btrfs_fs_info *fs_info = qgroup_kobj_to_fs_info(qgroup_kobj);	\
+	struct btrfs_qgroup *qgroup = container_of(qgroup_kobj,			\
+			struct btrfs_qgroup, kobj);				\
+	return btrfs_show_u64(&qgroup->_member, &fs_info->qgroup_lock, buf);	\
+}										\
+BTRFS_ATTR(qgroup, _show_name, btrfs_qgroup_show_##_member)
+
+#define QGROUP_RSV_ATTR(_name, _type)						\
+static ssize_t btrfs_qgroup_rsv_show_##_name(struct kobject *qgroup_kobj,	\
+					     struct kobj_attribute *a,		\
+					     char *buf)				\
+{										\
+	struct btrfs_fs_info *fs_info = qgroup_kobj_to_fs_info(qgroup_kobj);	\
+	struct btrfs_qgroup *qgroup = container_of(qgroup_kobj,			\
+			struct btrfs_qgroup, kobj);				\
+	return btrfs_show_u64(&qgroup->rsv.values[_type],			\
+			&fs_info->qgroup_lock, buf);				\
+}										\
+BTRFS_ATTR(qgroup, rsv_##_name, btrfs_qgroup_rsv_show_##_name)
+
+QGROUP_ATTR(rfer, referenced);
+QGROUP_ATTR(excl, exclusive);
+QGROUP_ATTR(max_rfer, max_referenced);
+QGROUP_ATTR(max_excl, max_exclusive);
+QGROUP_ATTR(lim_flags, limit_flags);
+QGROUP_RSV_ATTR(data, BTRFS_QGROUP_RSV_DATA);
+QGROUP_RSV_ATTR(meta_pertrans, BTRFS_QGROUP_RSV_META_PERTRANS);
+QGROUP_RSV_ATTR(meta_prealloc, BTRFS_QGROUP_RSV_META_PREALLOC);
+
+static struct attribute *qgroup_attrs[] = {
+	BTRFS_ATTR_PTR(qgroup, referenced),
+	BTRFS_ATTR_PTR(qgroup, exclusive),
+	BTRFS_ATTR_PTR(qgroup, max_referenced),
+	BTRFS_ATTR_PTR(qgroup, max_exclusive),
+	BTRFS_ATTR_PTR(qgroup, limit_flags),
+	BTRFS_ATTR_PTR(qgroup, rsv_data),
+	BTRFS_ATTR_PTR(qgroup, rsv_meta_pertrans),
+	BTRFS_ATTR_PTR(qgroup, rsv_meta_prealloc),
+	NULL
+};
+ATTRIBUTE_GROUPS(qgroup);
+
+static void qgroup_release(struct kobject *kobj)
+{
+	struct btrfs_qgroup *qgroup = container_of(kobj, struct btrfs_qgroup, kobj);
+
+	memset(&qgroup->kobj, 0, sizeof(*kobj));
+}
+
+static struct kobj_type qgroup_ktype = {
+	.sysfs_ops = &kobj_sysfs_ops,
+	.release = qgroup_release,
+	.default_groups = qgroup_groups,
+};
+
+int btrfs_sysfs_add_one_qgroup(struct btrfs_fs_info *fs_info,
+				struct btrfs_qgroup *qgroup)
+{
+	struct kobject *qgroups_kobj = fs_info->qgroups_kobj;
+	int ret;
+
+	if (test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state))
+		return 0;
+	if (qgroup->kobj.state_initialized)
+		return 0;
+	if (!qgroups_kobj)
+		return -EINVAL;
+
+	ret = kobject_init_and_add(&qgroup->kobj, &qgroup_ktype, qgroups_kobj,
+			"%hu_%llu", btrfs_qgroup_level(qgroup->qgroupid),
+			btrfs_qgroup_subvolid(qgroup->qgroupid));
+	if (ret < 0)
+		kobject_put(&qgroup->kobj);
+
+	return ret;
+}
+
+void btrfs_sysfs_del_qgroups(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_qgroup *qgroup;
+	struct btrfs_qgroup *next;
+
+	if (test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state))
+		return;
+
+	rbtree_postorder_for_each_entry_safe(qgroup, next,
+					     &fs_info->qgroup_tree, node)
+		btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
+	kobject_del(fs_info->qgroups_kobj);
+	kobject_put(fs_info->qgroups_kobj);
+	fs_info->qgroups_kobj = NULL;
+}
+
+/* Called when qgroups get initialized, thus there is no need for locking */
+int btrfs_sysfs_add_qgroups(struct btrfs_fs_info *fs_info)
+{
+	struct kobject *fsid_kobj = &fs_info->fs_devices->fsid_kobj;
+	struct btrfs_qgroup *qgroup;
+	struct btrfs_qgroup *next;
+	int ret = 0;
+
+	if (test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state))
+		return 0;
+
+	ASSERT(fsid_kobj);
+	if (fs_info->qgroups_kobj)
+		return 0;
+
+	fs_info->qgroups_kobj = kobject_create_and_add("qgroups", fsid_kobj);
+	if (!fs_info->qgroups_kobj) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	rbtree_postorder_for_each_entry_safe(qgroup, next,
+					     &fs_info->qgroup_tree, node) {
+		ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
+		if (ret < 0)
+			goto out;
+	}
+
+out:
+	if (ret < 0)
+		btrfs_sysfs_del_qgroups(fs_info);
+	return ret;
+}
+
+void btrfs_sysfs_del_one_qgroup(struct btrfs_fs_info *fs_info,
+				struct btrfs_qgroup *qgroup)
+{
+	if (test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state))
+		return;
+
+	if (qgroup->kobj.state_initialized) {
+		kobject_del(&qgroup->kobj);
+		kobject_put(&qgroup->kobj);
+	}
+}
 
 /*
  * Change per-fs features in /sys/fs/btrfs/UUID/features to match current