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

This patch try to add a check before creating/destroying a qgroup.

Signed-off-by: Wang Shilong <wangsl-f...@cn.fujitsu.com>
Reviewed-by: Miao Xie <mi...@cn.fujitsu.com>
---
 fs/btrfs/ioctl.c |   41 ++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 40 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3c4fde0..8a01326 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3784,6 +3784,42 @@ drop_write:
        return ret;
 }
 
+static int may_qgroup_create(struct btrfs_root *root,
+                            struct btrfs_ioctl_qgroup_create_args *sa)
+{
+       int ret = 0;
+       struct btrfs_key key;
+       struct btrfs_path *path;
+
+       if (!root->fs_info->quota_root)
+               return -EINVAL;
+
+       path = btrfs_alloc_path();
+       if (!path) {
+               ret = -ENOMEM;
+               return ret;
+       }
+
+       key.objectid = 0;
+       key.type = BTRFS_QGROUP_INFO_KEY;
+       key.offset = sa->qgroupid;
+
+       ret = btrfs_search_slot(NULL, root->fs_info->quota_root,
+                               &key, path, 0, 0);
+       if (sa->create) {
+               if (!ret)
+                       ret = -EEXIST;
+               if (ret > 0)
+                       ret = 0;
+               goto out;
+       }
+       if (ret > 0)
+               ret = -ENOENT;
+out:
+       btrfs_free_path(path);
+       return ret;
+}
+
 static long btrfs_ioctl_qgroup_create(struct file *file, void __user *arg)
 {
        struct btrfs_root *root = BTRFS_I(file_inode(file))->root;
@@ -3810,13 +3846,16 @@ static long btrfs_ioctl_qgroup_create(struct file 
*file, void __user *arg)
                goto out;
        }
        mutex_lock(&root->fs_info->quota_lock);
+       ret = may_qgroup_create(root, sa);
+       if (ret)
+               goto out_unlock;
+
        trans = btrfs_join_transaction(root);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                goto out_unlock;
        }
 
-       /* FIXME: check if the IDs really exist */
        if (sa->create) {
                ret = btrfs_create_qgroup(trans, root->fs_info, sa->qgroupid,
                                          NULL);
-- 
1.7.7.6

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