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>

fs/btrfs/ctree.h

@@ -779,6 +779,7 @@ struct btrfs_fs_info {
 	u32 thread_pool_size;
 
 	struct kobject *space_info_kobj;
+	struct kobject *qgroups_kobj;
 
 	u64 total_pinned;
 

fs/btrfs/qgroup.c

@@ -22,6 +22,7 @@
 #include "extent_io.h"
 #include "qgroup.h"
 #include "block-group.h"
+#include "sysfs.h"
 
 /* TODO XXX FIXME
  *  - subvol delete -> delete when ref goes to 0? delete limits also?
@@ -220,10 +221,12 @@ static struct btrfs_qgroup *add_qgroup_rb(struct btrfs_fs_info *fs_info,
 	return qgroup;
 }
 
-static void __del_qgroup_rb(struct btrfs_qgroup *qgroup)
+static void __del_qgroup_rb(struct btrfs_fs_info *fs_info,
+			    struct btrfs_qgroup *qgroup)
 {
 	struct btrfs_qgroup_list *list;
 
+	btrfs_sysfs_del_one_qgroup(fs_info, qgroup);
 	list_del(&qgroup->dirty);
 	while (!list_empty(&qgroup->groups)) {
 		list = list_first_entry(&qgroup->groups,
@@ -252,7 +255,7 @@ static int del_qgroup_rb(struct btrfs_fs_info *fs_info, u64 qgroupid)
 		return -ENOENT;
 
 	rb_erase(&qgroup->node, &fs_info->qgroup_tree);
-	__del_qgroup_rb(qgroup);
+	__del_qgroup_rb(fs_info, qgroup);
 	return 0;
 }
 
@@ -351,6 +354,9 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
 		goto out;
 	}
 
+	ret = btrfs_sysfs_add_qgroups(fs_info);
+	if (ret < 0)
+		goto out;
 	/* default this to quota off, in case no status key is found */
 	fs_info->qgroup_flags = 0;
 
@@ -412,6 +418,10 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
 				goto out;
 			}
 		}
+		ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
+		if (ret < 0)
+			goto out;
+
 		switch (found_key.type) {
 		case BTRFS_QGROUP_INFO_KEY: {
 			struct btrfs_qgroup_info_item *ptr;
@@ -500,16 +510,12 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
 		ulist_free(fs_info->qgroup_ulist);
 		fs_info->qgroup_ulist = NULL;
 		fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+		btrfs_sysfs_del_qgroups(fs_info);
 	}
 
 	return ret < 0 ? ret : 0;
 }
 
-static u64 btrfs_qgroup_subvolid(u64 qgroupid)
-{
-	return (qgroupid & ((1ULL << BTRFS_QGROUP_LEVEL_SHIFT) - 1));
-}
-
 /*
  * Called in close_ctree() when quota is still enabled.  This verifies we don't
  * leak some reserved space.
@@ -562,7 +568,7 @@ void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info)
 	while ((n = rb_first(&fs_info->qgroup_tree))) {
 		qgroup = rb_entry(n, struct btrfs_qgroup, node);
 		rb_erase(n, &fs_info->qgroup_tree);
-		__del_qgroup_rb(qgroup);
+		__del_qgroup_rb(fs_info, qgroup);
 	}
 	/*
 	 * We call btrfs_free_qgroup_config() when unmounting
@@ -571,6 +577,7 @@ void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info)
 	 */
 	ulist_free(fs_info->qgroup_ulist);
 	fs_info->qgroup_ulist = NULL;
+	btrfs_sysfs_del_qgroups(fs_info);
 }
 
 static int add_qgroup_relation_item(struct btrfs_trans_handle *trans, u64 src,
@@ -943,6 +950,9 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
 		goto out;
 	}
 
+	ret = btrfs_sysfs_add_qgroups(fs_info);
+	if (ret < 0)
+		goto out;
 	/*
 	 * 1 for quota root item
 	 * 1 for BTRFS_QGROUP_STATUS item
@@ -1030,6 +1040,11 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
 				btrfs_abort_transaction(trans, ret);
 				goto out_free_path;
 			}
+			ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
+			if (ret < 0) {
+				btrfs_abort_transaction(trans, ret);
+				goto out_free_path;
+			}
 		}
 		ret = btrfs_next_item(tree_root, path);
 		if (ret < 0) {
@@ -1054,6 +1069,11 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
 		btrfs_abort_transaction(trans, ret);
 		goto out_free_path;
 	}
+	ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
+	if (ret < 0) {
+		btrfs_abort_transaction(trans, ret);
+		goto out_free_path;
+	}
 
 	ret = btrfs_commit_transaction(trans);
 	trans = NULL;
@@ -1089,6 +1109,7 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info)
 		fs_info->qgroup_ulist = NULL;
 		if (trans)
 			btrfs_end_transaction(trans);
+		btrfs_sysfs_del_qgroups(fs_info);
 	}
 	mutex_unlock(&fs_info->qgroup_ioctl_lock);
 	return ret;
@@ -1441,8 +1462,11 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
 	qgroup = add_qgroup_rb(fs_info, qgroupid);
 	spin_unlock(&fs_info->qgroup_lock);
 
-	if (IS_ERR(qgroup))
+	if (IS_ERR(qgroup)) {
 		ret = PTR_ERR(qgroup);
+		goto out;
+	}
+	ret = btrfs_sysfs_add_one_qgroup(fs_info, qgroup);
 out:
 	mutex_unlock(&fs_info->qgroup_ioctl_lock);
 	return ret;
@@ -2861,6 +2885,8 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
 
 unlock:
 	spin_unlock(&fs_info->qgroup_lock);
+	if (!ret)
+		ret = btrfs_sysfs_add_one_qgroup(fs_info, dstgroup);
 out:
 	if (!committing)
 		mutex_unlock(&fs_info->qgroup_ioctl_lock);

fs/btrfs/qgroup.h

@@ -8,6 +8,7 @@
 
 #include <linux/spinlock.h>
 #include <linux/rbtree.h>
+#include <linux/kobject.h>
 #include "ulist.h"
 #include "delayed-ref.h"
 
@@ -223,8 +224,18 @@ struct btrfs_qgroup {
 	 */
 	u64 old_refcnt;
 	u64 new_refcnt;
+
+	/*
+	 * Sysfs kobjectid
+	 */
+	struct kobject kobj;
 };
 
+static inline u64 btrfs_qgroup_subvolid(u64 qgroupid)
+{
+	return (qgroupid & ((1ULL << BTRFS_QGROUP_LEVEL_SHIFT) - 1));
+}
+
 /*
  * For qgroup event trace points only
  */

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 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 	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

fs/btrfs/sysfs.h

@@ -36,4 +36,11 @@ int btrfs_sysfs_add_space_info_type(struct btrfs_fs_info *fs_info,
 void btrfs_sysfs_remove_space_info(struct btrfs_space_info *space_info);
 void btrfs_sysfs_update_devid(struct btrfs_device *device);
 
+int btrfs_sysfs_add_one_qgroup(struct btrfs_fs_info *fs_info,
+				struct btrfs_qgroup *qgroup);
+void btrfs_sysfs_del_qgroups(struct btrfs_fs_info *fs_info);
+int btrfs_sysfs_add_qgroups(struct btrfs_fs_info *fs_info);
+void btrfs_sysfs_del_one_qgroup(struct btrfs_fs_info *fs_info,
+				struct btrfs_qgroup *qgroup);
+
 #endif