fs: warn about impending deprecation of mandatory locks

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>

diff --git a/fs/namespace.c b/fs/namespace.c
index ab4174a..2279473 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1716,8 +1716,12 @@ static inline bool may_mount(void)
 }
 
 #ifdef CONFIG_MANDATORY_FILE_LOCKING
-static inline bool may_mandlock(void)
+static bool may_mandlock(void)
 {
+       pr_warn_once("======================================================\n"
+                    "WARNING: the mand mount option is being deprecated and\n"
+                    "         will be removed in v5.15!\n"
+                    "======================================================\n");
        return capable(CAP_SYS_ADMIN);
 }
 #else