Merge tag 'for-linus-2019-11-08' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:

 - Two NVMe device removal crash fixes, and a compat fixup for for an
   ioctl that was introduced in this release (Anton, Charles, Max - via
   Keith)

 - Missing error path mutex unlock for drbd (Dan)

 - cgroup writeback fixup on dead memcg (Tejun)

 - blkcg online stats print fix (Tejun)

* tag 'for-linus-2019-11-08' of git://git.kernel.dk/linux-block:
  cgroup,writeback: don't switch wbs immediately on dead wbs if the memcg is dead
  block: drbd: remove a stray unlock in __drbd_send_protocol()
  blkcg: make blkcg_print_stat() print stats only for online blkgs
  nvme: change nvme_passthru_cmd64 to explicitly mark rsvd
  nvme-multipath: fix crash in nvme_mpath_clear_ctrl_paths
  nvme-rdma: fix a segmentation fault during module unload

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8461a6322039..335607b8c5c0 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -576,10 +576,13 @@ void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
 	spin_unlock(&inode->i_lock);
 
 	/*
-	 * A dying wb indicates that the memcg-blkcg mapping has changed
-	 * and a new wb is already serving the memcg.  Switch immediately.
+	 * A dying wb indicates that either the blkcg associated with the
+	 * memcg changed or the associated memcg is dying.  In the first
+	 * case, a replacement wb should already be available and we should
+	 * refresh the wb immediately.  In the second case, trying to
+	 * refresh will keep failing.
 	 */
-	if (unlikely(wb_dying(wbc->wb)))
+	if (unlikely(wb_dying(wbc->wb) && !css_is_dying(wbc->wb->memcg_css)))
 		inode_switch_wbs(inode, wbc->wb_id);
 }
 EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode);