writeback: synchronize sync(2) against cgroup writeback membership switches

[sfrench/cifs-2.6.git] / include / linux / backing-dev-defs.h

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index c31157135598150332d3aa193764c39e18f247b2..07e02d6df5ad9f24b262fe2d852e21235de8119f 100644 (file)
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -190,6 +190,7 @@ struct backing_dev_info {
        struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
        struct rb_root cgwb_congested_tree; /* their congested states */
        struct mutex cgwb_release_mutex;  /* protect shutdown of wb structs */
+       struct rw_semaphore wb_switch_rwsem; /* no cgwb switch while syncing */
 #else
        struct bdi_writeback_congested *wb_congested;
 #endif