1 files changed, 9 insertions, 2 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 5a5d79ee256f..d5eb4ad1c534 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <linux/blkdev.h>
 #include <linux/writeback.h>
+#include <linux/memcontrol.h>
 #include <linux/blk-cgroup.h>
 #include <linux/backing-dev-defs.h>
 #include <linux/slab.h>
@@ -252,13 +253,19 @@ int inode_congested(struct inode *inode, int cong_bits);
  * @inode: inode of interest
  *
  * cgroup writeback requires support from both the bdi and filesystem.
- * Test whether @inode has both.
+ * Also, both memcg and iocg have to be on the default hierarchy.  Test
+ * whether all conditions are met.
+ *
+ * Note that the test result may change dynamically on the same inode
+ * depending on how memcg and iocg are configured.
  */
 static inline bool inode_cgwb_enabled(struct inode *inode)
 {
         struct backing_dev_info *bdi = inode_to_bdi(inode);
 
-        return bdi_cap_account_dirty(bdi) &&
+        return cgroup_on_dfl(mem_cgroup_root_css->cgroup) &&
+                cgroup_on_dfl(blkcg_root_css->cgroup) &&
+                bdi_cap_account_dirty(bdi) &&
                 (bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
                 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
 }