NFSv4: Avoid unnecessary scans of filesystems for expired delegations

NFSv4: Avoid unnecessary scans of filesystems for expired delegations

[ Upstream commit f163aa81a799e2d46d7f8f0b42a0e7770eaa0d06 ]

The amount of looping through the list of delegations is occasionally
leading to soft lockups.  If the state manager was asked to reap the
expired delegations, it should scan only those filesystems that hold
delegations that need to be reaped.

Fixes: 7f156ef0bf45 ("NFSv4: Clean up nfs_delegation_reap_expired()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>