• Wang Shilong's avatar
    Btrfs: introduce a mutex lock for btrfs quota operations · f2f6ed3d
    Wang Shilong authored
    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: default avatarWang Shilong <wangsl-fnst@cn.fujitsu.com>
    Reviewed-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
    Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
    f2f6ed3d
qgroup.c 40.2 KB