[PATCH v2 2/2] btrfs: qgroup: add sysfs interface for debug

Qu Wenruo
2020-06-28T05:08:21Z

This patch will add the following sysfs interface:
/sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/reference
/sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/exclusive
/sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/max_reference
/sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/max_exclusive
/sys/fs/btrfs/<UUID>/qgroups/<qgroup_id>/limit_flags
^^^ Above are already in "btrfs qgroup show" command output ^^^

/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 I want this interface to
be included into production build so we could have an easier life to
debug qgroup rsv related bugs.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
fs/btrfs/ctree.h | 1 +
fs/btrfs/qgroup.c | 44 +++++++++++---
fs/btrfs/qgroup.h | 11 ++++
fs/btrfs/sysfs.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/sysfs.h | 6 ++
5 files changed, 204 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d8301bf240e0..9c0394893e8e 100644
--- a/fs/btrfs/ctree.h
+++ b/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;

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 014d32429165..fc90ec0a86f1 100644
--- a/fs/btrfs/qgroup.c
+++ b/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);
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index 3be5198a3719..0116779d34e5 100644
--- a/fs/btrfs/qgroup.h
+++ b/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
*/
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index a39bff64ff24..3d7a939601a9 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 +1456,156 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
return error;
}

+static 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, reference);
+QGROUP_ATTR(excl, exclusive);
+QGROUP_ATTR(max_rfer, max_reference);
+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, reference),
+ BTRFS_ATTR_PTR(qgroup, exclusive),
+ BTRFS_ATTR_PTR(qgroup, max_reference),
+ 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 qgroup get initialized, thus there is no need for extra lock. */
+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
diff --git a/fs/btrfs/sysfs.h b/fs/btrfs/sysfs.h
index 718a26c97833..1e27a9c94c84 100644
--- a/fs/btrfs/sysfs.h
+++ b/fs/btrfs/sysfs.h
@@ -36,4 +36,10 @@ 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
--
2.27.0