Btrfs: introduce a mutex lock for btrfs quota operations

The original code has one spin_lock 'qgroup_lock' to protect quota
configurations in memory. If we want to add a BTRFS_QGROUP_INFO_KEY,
it will be added to Btree firstly, and then update configurations in
memory,however, a race condition may happen between these operations.
For example:
	->add_qgroup_info_item()
		->add_qgroup_rb()

For the above case, del_qgroup_info_item() may happen just before
add_qgroup_rb().

What's worse, when we want to add a qgroup relation:
	->add_qgroup_relation_item()
		->add_qgroup_relations()

We don't have any checks whether 'src' and 'dst' exist before
add_qgroup_relation_item(), a race condition can also happen for
the above case.

To avoid race condition and have all the necessary checks, we introduce
a mutex lock 'qgroup_ioctl_lock', and we make all the user change operations
protected by the mutex lock.

Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 075a8a0..1a85040 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1583,6 +1583,9 @@ struct btrfs_fs_info {
        struct rb_root qgroup_tree;
        spinlock_t qgroup_lock;
 
+       /* protect user change for quota operations */
+       struct mutex qgroup_ioctl_lock;
+
        /* list of dirty qgroups to be written at next commit */
        struct list_head dirty_qgroups;
 

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 70e6b0c..9f83e5b 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2213,6 +2213,7 @@ int open_ctree(struct super_block *sb,
        mutex_init(&fs_info->dev_replace.lock);
 
        spin_lock_init(&fs_info->qgroup_lock);
+       mutex_init(&fs_info->qgroup_ioctl_lock);
        fs_info->qgroup_tree = RB_ROOT;
        INIT_LIST_HEAD(&fs_info->dirty_qgroups);
        fs_info->qgroup_seq = 1;

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 5be5a39..0a1f686 100644 (file)
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -791,6 +791,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
        int ret = 0;
        int slot;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        spin_lock(&fs_info->qgroup_lock);
        if (fs_info->quota_root) {
                fs_info->pending_quota_state = 1;
@@ -900,6 +901,7 @@ out_free_root:
                kfree(quota_root);
        }
 out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -910,10 +912,11 @@ int btrfs_quota_disable(struct btrfs_trans_handle *trans,
        struct btrfs_root *quota_root;
        int ret = 0;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        spin_lock(&fs_info->qgroup_lock);
        if (!fs_info->quota_root) {
                spin_unlock(&fs_info->qgroup_lock);
-               return 0;
+               goto out;
        }
        fs_info->quota_enabled = 0;
        fs_info->pending_quota_state = 0;
@@ -922,8 +925,10 @@ int btrfs_quota_disable(struct btrfs_trans_handle *trans,
        btrfs_free_qgroup_config(fs_info);
        spin_unlock(&fs_info->qgroup_lock);
 
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        ret = btrfs_clean_quota_tree(trans, quota_root);
        if (ret)
@@ -944,6 +949,7 @@ int btrfs_quota_disable(struct btrfs_trans_handle *trans,
        free_extent_buffer(quota_root->commit_root);
        kfree(quota_root);
 out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -959,24 +965,28 @@ int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
        struct btrfs_root *quota_root;
        int ret = 0;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        quota_root = fs_info->quota_root;
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        ret = add_qgroup_relation_item(trans, quota_root, src, dst);
        if (ret)
-               return ret;
+               goto out;
 
        ret = add_qgroup_relation_item(trans, quota_root, dst, src);
        if (ret) {
                del_qgroup_relation_item(trans, quota_root, src, dst);
-               return ret;
+               goto out;
        }
 
        spin_lock(&fs_info->qgroup_lock);
        ret = add_relation_rb(quota_root->fs_info, src, dst);
        spin_unlock(&fs_info->qgroup_lock);
-
+out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -987,9 +997,12 @@ int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
        int ret = 0;
        int err;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        quota_root = fs_info->quota_root;
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        ret = del_qgroup_relation_item(trans, quota_root, src, dst);
        err = del_qgroup_relation_item(trans, quota_root, dst, src);
@@ -1000,7 +1013,8 @@ int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
        del_relation_rb(fs_info, src, dst);
 
        spin_unlock(&fs_info->qgroup_lock);
-
+out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -1011,9 +1025,12 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans,
        struct btrfs_qgroup *qgroup;
        int ret = 0;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        quota_root = fs_info->quota_root;
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        ret = add_qgroup_item(trans, quota_root, qgroupid);
 
@@ -1023,7 +1040,8 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans,
 
        if (IS_ERR(qgroup))
                ret = PTR_ERR(qgroup);
-
+out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -1034,9 +1052,12 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
        struct btrfs_qgroup *qgroup;
        int ret = 0;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        quota_root = fs_info->quota_root;
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        /* check if there are no relations to this qgroup */
        spin_lock(&fs_info->qgroup_lock);
@@ -1044,7 +1065,8 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
        if (qgroup) {
                if (!list_empty(&qgroup->groups) || !list_empty(&qgroup->members)) {
                        spin_unlock(&fs_info->qgroup_lock);
-                       return -EBUSY;
+                       ret = -EBUSY;
+                       goto out;
                }
        }
        spin_unlock(&fs_info->qgroup_lock);
@@ -1054,7 +1076,8 @@ int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
        spin_lock(&fs_info->qgroup_lock);
        del_qgroup_rb(quota_root->fs_info, qgroupid);
        spin_unlock(&fs_info->qgroup_lock);
-
+out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -1062,12 +1085,16 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
                       struct btrfs_fs_info *fs_info, u64 qgroupid,
                       struct btrfs_qgroup_limit *limit)
 {
-       struct btrfs_root *quota_root = fs_info->quota_root;
+       struct btrfs_root *quota_root;
        struct btrfs_qgroup *qgroup;
        int ret = 0;
 
-       if (!quota_root)
-               return -EINVAL;
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
+       quota_root = fs_info->quota_root;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        ret = update_qgroup_limit_item(trans, quota_root, qgroupid,
                                       limit->flags, limit->max_rfer,
@@ -1094,7 +1121,8 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
 
 unlock:
        spin_unlock(&fs_info->qgroup_lock);
-
+out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }
 
@@ -1392,11 +1420,14 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
        struct btrfs_qgroup *dstgroup;
        u32 level_size = 0;
 
+       mutex_lock(&fs_info->qgroup_ioctl_lock);
        if (!fs_info->quota_enabled)
-               return 0;
+               goto out;
 
-       if (!quota_root)
-               return -EINVAL;
+       if (!quota_root) {
+               ret = -EINVAL;
+               goto out;
+       }
 
        /*
         * create a tracking group for the subvol itself
@@ -1523,6 +1554,7 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 unlock:
        spin_unlock(&fs_info->qgroup_lock);
 out:
+       mutex_unlock(&fs_info->qgroup_ioctl_lock);
        return ret;
 }