stable inclusion
from linux-4.19.99
commit 9ed8e8f6844dc84ba115c732f5e04c5e8c257422

--------------------------------

[ Upstream commit 108bb4af ]

If the attempt to instantiate the mirror's layout DS pointer failed,
then that pointer may hold a value of type ERR_PTR(), so we need
to check that before we dereference it.

Fixes: 65990d1a ("pNFS/flexfiles: Fix a deadlock on LAYOUTGET")
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>