[PATCH v7 02/13] printk: Use effective loglevel for suppression and extended console state

[Chris Down <chris@chrisdown.name>]

In preparation for supporting per-console loglevels, modify
printk_get_next_message() to accept the effective console loglevel
instead of individual arguments that mimic console fields. This keeps
the function console-agnostic and lockless as intended, while still
allowing per-console loglevel support to be added in later patches.

devkmsg_read() uses CONSOLE_LOGLEVEL_MOTORMOUTH to never suppress
messages. All other consoles pass their effective loglevel (currently
console_loglevel, will be per-console in later patches).

Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Chris Down <chris@chrisdown.name>
---
 kernel/printk/internal.h |  2 +-
 kernel/printk/nbcon.c    |  2 +-
 kernel/printk/printk.c   | 22 +++++++++++++---------
 3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index f72bbfa266d6..1ed86577896c 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -333,7 +333,7 @@ struct printk_message {
 };
 
 bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
-			     bool is_extended, bool may_supress);
+			     bool is_extended, int con_eff_level);
 
 #ifdef CONFIG_PRINTK
 void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 558ef3177976..eb4c8faa213d 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -993,7 +993,7 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
 	if (!nbcon_context_enter_unsafe(ctxt))
 		return false;
 
-	ctxt->backlog = printk_get_next_message(&pmsg, ctxt->seq, is_extended, true);
+	ctxt->backlog = printk_get_next_message(&pmsg, ctxt->seq, is_extended, console_loglevel);
 	if (!ctxt->backlog)
 		return nbcon_context_exit_unsafe(ctxt);
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ff8b6dbb29a7..745f89a18189 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -807,7 +807,8 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 	if (ret)
 		return ret;
 
-	if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true, false)) {
+	if (!printk_get_next_message(&pmsg, atomic64_read(&user->seq), true,
+				     CONSOLE_LOGLEVEL_MOTORMOUTH)) {
 		if (file->f_flags & O_NONBLOCK) {
 			ret = -EAGAIN;
 			goto out;
@@ -825,7 +826,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
 		 */
 		ret = wait_event_interruptible(log_wait,
 				printk_get_next_message(&pmsg, atomic64_read(&user->seq), true,
-							false)); /* LMM(devkmsg_read:A) */
+							CONSOLE_LOGLEVEL_MOTORMOUTH)); /* LMM(devkmsg_read:A) */
 		if (ret)
 			goto out;
 	}
@@ -1279,9 +1280,9 @@ 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 suppress_message_printing(int level, int con_eff_level)
 {
-	return (level >= console_loglevel && !ignore_loglevel);
+	return (level >= con_eff_level && !ignore_loglevel);
 }
 
 #ifdef CONFIG_BOOT_PRINTK_DELAY
@@ -2115,7 +2116,7 @@ int printk_delay_msec __read_mostly;
 static inline void printk_delay(int level)
 {
 	/* If the message is forced (e.g. panic), we must delay */
-	if (!is_printk_force_console() && suppress_message_printing(level))
+	if (!is_printk_force_console() && suppress_message_printing(level, console_loglevel))
 		return;
 
 	boot_delay_msec();
@@ -2946,14 +2947,15 @@ void console_prepend_replay(struct printk_message *pmsg)
  * @is_extended specifies if the message should be formatted for extended
  * console output.
  *
- * @may_supress specifies if records may be skipped based on loglevel.
+ * @con_eff_level is the effective console loglevel to use for suppression
+ * checks.
  *
  * Returns false if no record is available. Otherwise true and all fields
  * of @pmsg are valid. (See the documentation of struct printk_message
  * for information about the @pmsg fields.)
  */
 bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
-			     bool is_extended, bool may_suppress)
+			     bool is_extended, int con_eff_level)
 {
 	struct printk_buffers *pbufs = pmsg->pbufs;
 	const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
@@ -2982,13 +2984,14 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
 
 	pmsg->seq = r.info->seq;
 	pmsg->dropped = r.info->seq - seq;
+
 	force_con = r.info->flags & LOG_FORCE_CON;
 
 	/*
 	 * Skip records that are not forced to be printed on consoles and that
 	 * has level above the console loglevel.
 	 */
-	if (!force_con && may_suppress && suppress_message_printing(r.info->level))
+	if (!force_con && suppress_message_printing(r.info->level, con_eff_level))
 		goto out;
 
 	if (is_extended) {
@@ -3064,7 +3067,8 @@ static bool console_emit_next_record(struct console *con, bool *handover, int co
 
 	*handover = false;
 
-	if (!printk_get_next_message(&pmsg, con->seq, is_extended, true))
+	if (!printk_get_next_message(&pmsg, con->seq, is_extended,
+				     console_loglevel))
 		return false;
 
 	con->dropped += pmsg.dropped;
-- 
2.51.2