fs: warn about impending deprecation of mandatory locks

stable inclusion
from stable-5.10.61
commit 0d5fcfc6406ee7138ca0141769f90a37d4b4ae8b
bugzilla: 177029 https://gitee.com/openeuler/kernel/issues/I4EAXD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0d5fcfc6406ee7138ca0141769f90a37d4b4ae8b



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[ Upstream commit fdd92b64 ]

We've had CONFIG_MANDATORY_FILE_LOCKING since 2015 and a lot of distros
have disabled it. Warn the stragglers that still use "-o mand" that
we'll be dropping support for that mount option.

Cc: stable@vger.kernel.org
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>