cifs: release cached dentries only if mount is complete

cifs: release cached dentries only if mount is complete

[ Upstream commit d788e51636462e61c6883f7d96b07b06bc291650 ]

During cifs_kill_sb, we first dput all the dentries that we have cached.
However this function can also get called for mount failures.
So dput the cached dentries only if the filesystem mount is complete.
i.e. cifs_sb->root is populated.

Fixes: 5e9c89d43fa6 ("cifs: Grab a reference for the dentry of the cached directory during the lifetime of the cache")
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>