[RFC PATCH] printk: Possible solution for loglevel manipulation by earlyparams

[Petr Mladek]

Early params that manipulate console_loglevel should invalidate
LOG_NOCONS flag for all the existing messages.
---
 include/linux/console.h |  2 ++
 init/main.c             |  6 +++---
 kernel/printk/printk.c  | 27 +++++++++++++++++++++++----
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/include/linux/console.h b/include/linux/console.h
index ec9bdb3d7bab..3d3f7ab8f82e 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -195,6 +195,8 @@ extern bool console_suspend_enabled;
 extern void suspend_console(void);
 extern void resume_console(void);
 
+extern void console_set_default_loglevel(int loglevel);
+
 int mda_console_init(void);
 void prom_con_init(void);
 
diff --git a/init/main.c b/init/main.c
index 18f8f0140fa0..936466209494 100644
--- a/init/main.c
+++ b/init/main.c
@@ -213,13 +213,13 @@ EXPORT_SYMBOL(loops_per_jiffy);
 
 static int __init debug_kernel(char *str)
 {
-	console_loglevel = CONSOLE_LOGLEVEL_DEBUG;
+	console_set_default_loglevel(CONSOLE_LOGLEVEL_DEBUG);
 	return 0;
 }
 
 static int __init quiet_kernel(char *str)
 {
-	console_loglevel = CONSOLE_LOGLEVEL_QUIET;
+	console_set_default_loglevel(CONSOLE_LOGLEVEL_QUIET);
 	return 0;
 }
 
@@ -236,7 +236,7 @@ static int __init loglevel(char *str)
 	 * are quite hard to debug
 	 */
 	if (get_option(&str, &newlevel)) {
-		console_loglevel = newlevel;
+		console_set_default_loglevel(newlevel);
 		return 0;
 	}
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 924e37fb1620..b5a0074302e9 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -430,6 +430,9 @@ static u32 console_idx;
 static u64 clear_seq;
 static u32 clear_idx;
 
+/* Invalidate nocons flag setting before early param are proceed */
+static u64 console_valid_nocons_seq;
+
 #define PREFIX_MAX		32
 #define LOG_LINE_MAX		(1024 - PREFIX_MAX)
 
@@ -1148,11 +1151,19 @@ module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(ignore_loglevel,
 		 "ignore loglevel setting (prints all kernel messages to the console)");
 
-static bool suppress_message_printing(int level)
+static bool nocons_loglevel(int level)
 {
 	return (level >= console_loglevel && !ignore_loglevel);
 }
 
+static bool nocons_msg(struct printk_log *msg)
+{
+	if (console_seq >= console_valid_nocons_seq)
+		return msg->flags & LOG_NOCONS;
+
+	return nocons_loglevel(msg->level);
+}
+
 #ifdef CONFIG_BOOT_PRINTK_DELAY
 
 static int boot_delay; /* msecs delay after each printk during bootup */
@@ -1182,7 +1193,7 @@ static void boot_delay_msec(int level)
 	unsigned long timeout;
 
 	if ((boot_delay == 0 || system_state >= SYSTEM_RUNNING)
-		|| suppress_message_printing(level)) {
+		|| nocons_loglevel(level)) {
 		return;
 	}
 
@@ -1882,7 +1893,7 @@ int vprintk_store(int facility, int level,
 	if (dict)
 		lflags |= LOG_PREFIX|LOG_NEWLINE;
 
-	if (suppress_message_printing(level))
+	if (nocons_loglevel(level))
 		lflags |= LOG_NOCONS;
 
 	return log_output(facility, level, lflags,
@@ -2031,6 +2042,7 @@ static void console_lock_spinning_enable(void) { }
 static int console_lock_spinning_disable_and_check(void) { return 0; }
 static void call_console_drivers(const char *ext_text, size_t ext_len,
 				 const char *text, size_t len) {}
+static bool nocons_msg(struct printk_log *msg) { return false; }
 static size_t msg_print_text(const struct printk_log *msg,
 			     bool syslog, char *buf, size_t size) { return 0; }
 
@@ -2197,6 +2209,13 @@ void resume_console(void)
 	console_unlock();
 }
 
+void console_set_default_loglevel(int loglevel)
+{
+	console_loglevel = loglevel;
+	/* Invalidate nocons flag for earlier messages. */
+	console_valid_nocons_seq = log_next_seq;
+}
+
 /**
  * console_cpu_notify - print deferred console messages after CPU hotplug
  * @cpu: unused
@@ -2369,7 +2388,7 @@ void console_unlock(void)
 			break;
 
 		msg = log_from_idx(console_idx);
-		if (msg->flags & LOG_NOCONS) {
+		if (nocons_msg(msg)) {
 			/*
 			 * Skip record if !ignore_loglevel, and
 			 * record has level above the console loglevel.
-- 
2.13.7