BDI is unregistered from del_gendisk() which is usually done in device's
release handler from device hotplug or error handling context, so BDI
can be unregistered anytime.

It should be normal for __mark_inode_dirty to see un-registered BDI,
so kill the WARN().

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Brian Foster <redacted>
Cc: Dave Chinner <redacted>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Ming Lei <redacted>
---
 fs/fs-writeback.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index a605c3dddabc..5e718580d4bf 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c

@@ -2318,10 +2318,6 @@ void __mark_inode_dirty(struct inode *inode, int flags)
 
 			wb = locked_inode_to_wb_and_lock_list(inode);
 
-			WARN(bdi_cap_writeback_dirty(wb->bdi) &&
-			     !test_bit(WB_registered, &wb->state),
-			     "bdi-%s not registered\n", bdi_dev_name(wb->bdi));
-
 			inode->dirtied_when = jiffies;
 			if (dirtytime)
 				inode->dirtied_time_when = jiffies;