fs: dlm: add deprecation Kconfig and warnings for timeouts

This patch adds a CONFIG_DLM_DEPRECATED_API Kconfig option
that must be enabled to use two timeout-related features
that we intend to remove in kernel v6.2.  Warnings are
printed if either is enabled and used.  Neither has ever
been used as far as we know.

. The DLM_LSFL_TIMEWARN lockspace creation flag will be
  removed, along with the associated configfs entry for
  setting the timeout.  Setting the flag and configfs file
  would cause dlm to track how long locks were waiting
  for reply messages.  After a timeout, a kernel message
  would be logged, and a netlink message would be sent
  to userspace.  Recently, midcomms messages have been
  added that produce much better logging about actual
  problems with messages.  No use has ever been found
  for the netlink messages.

. The userspace libdlm API has allowed the DLM_LKF_TIMEOUT
  flag with a timeout value to be set in lock requests.
  The lock request would be cancelled after the timeout.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/Kconfig

@@ -9,6 +9,15 @@ menuconfig DLM
 	A general purpose distributed lock manager for kernel or userspace
 	applications.
 
+config DLM_DEPRECATED_API
+	bool "DLM deprecated API"
+	depends on DLM
+	help
+	Enables deprecated DLM timeout features that will be removed in
+        later Linux kernel releases.
+
+	If you are unsure, say N.
+
 config DLM_DEBUG
 	bool "DLM debugging"
 	depends on DLM

fs/dlm/lockspace.c

@@ -489,8 +489,17 @@ static int new_lockspace(const char *name, const char *cluster,
 		ls->ls_ops_arg = ops_arg;
 	}
 
-	if (flags & DLM_LSFL_TIMEWARN)
+	if (flags & DLM_LSFL_TIMEWARN) {
+#ifdef CONFIG_DLM_DEPRECATED_API
+		pr_warn_once("===============================================================\n"
+			     "WARNING: the dlm DLM_LSFL_TIMEWARN flag is being deprecated and\n"
+			     "         will be removed in v6.2!\n"
+			     "         Inclusive DLM_LSFL_TIMEWARN define in UAPI header!\n"
+			     "===============================================================\n");
+#endif
+
 		set_bit(LSFL_TIMEWARN, &ls->ls_flags);
+	}
 
 	/* ls_exflags are forced to match among nodes, and we don't
 	   need to require all nodes to have some flags set */

fs/dlm/user.c

@@ -250,6 +250,14 @@ static int device_user_lock(struct dlm_user_proc *proc,
 		goto out;
 	}
 
+#ifdef CONFIG_DLM_DEPRECATED_API
+	if (params->timeout)
+		pr_warn_once("========================================================\n"
+			     "WARNING: the lkb timeout feature is being deprecated and\n"
+			     "         will be removed in v6.2!\n"
+			     "========================================================\n");
+#endif
+
 	ua = kzalloc(sizeof(struct dlm_user_args), GFP_NOFS);
 	if (!ua)
 		goto out;