[PATCH 6/7] Btrfs: remove unnecessary spin_lock holding for find_qgroup_rb()

[Wang Shilong]

From: Wang Shilong <wangsl-f...@cn.fujitsu.com>

Since mutex has been used for quota operations, we don't have to
hold spin_lock when calling find_qgroup_rb.

Signed-off-by: Wang Shilong <wangsl-f...@cn.fujitsu.com>
Reviewed-by: Miao Xie <mi...@cn.fujitsu.com>
---
 fs/btrfs/qgroup.c |   15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index e3598fa..e123d5c 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -98,7 +98,10 @@ struct btrfs_qgroup_list {
        struct btrfs_qgroup *member;
 };
 
-/* must be called with qgroup_lock held */
+/*
+ * don't need to be held by spin_lock, because it has been protected by
+ * quota_lock
+ */
 static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
                                           u64 qgroupid)
 {
@@ -1041,15 +1044,12 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle 
*trans,
                return -EINVAL;
 
        /* check if there are no relations to this qgroup */
-       spin_lock(&fs_info->qgroup_lock);
        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (qgroup) {
                if (!list_empty(&qgroup->groups) || 
!list_empty(&qgroup->members)) {
-                       spin_unlock(&fs_info->qgroup_lock);
                        return -EBUSY;
                }
        }
-       spin_unlock(&fs_info->qgroup_lock);
 
        ret = del_qgroup_item(trans, quota_root, qgroupid);
 
@@ -1081,22 +1081,19 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
                       (unsigned long long)qgroupid);
        }
 
-       spin_lock(&fs_info->qgroup_lock);
-
        qgroup = find_qgroup_rb(fs_info, qgroupid);
        if (!qgroup) {
                ret = -ENOENT;
-               goto unlock;
+               return ret;
        }
+       spin_lock(&fs_info->qgroup_lock);
        qgroup->lim_flags = limit->flags;
        qgroup->max_rfer = limit->max_rfer;
        qgroup->max_excl = limit->max_excl;
        qgroup->rsv_rfer = limit->rsv_rfer;
        qgroup->rsv_excl = limit->rsv_excl;
 
-unlock:
        spin_unlock(&fs_info->qgroup_lock);
-
        return ret;
 }
 
-- 
1.7.7.6

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