[PATCH v2 1/3] printk: introduce new macros pr_<level>_cont()

[Thomas Weißschuh]

These macros emit continuation messages with explicit levels.
In case the continuation is logged separately from the original message
it will retain its level instead of falling back to KERN_DEFAULT.

This remedies the issue that logs filtered by level contain stray
continuation messages without context.

Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
 include/linux/printk.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 8c81806c2e99..8f564c38f121 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -537,6 +537,8 @@ struct pi_entry {
  * This macro expands to a printk with KERN_CONT loglevel. It should only be
  * used when continuing a log message with no newline ('\n') enclosed. Otherwise
  * it defaults back to KERN_DEFAULT loglevel.
+ *
+ * Use the dedicated pr_<level>_cont() macros instead.
  */
 #define pr_cont(fmt, ...) \
 	printk(KERN_CONT fmt, ##__VA_ARGS__)
@@ -701,6 +703,27 @@ do {									\
 	no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
 #endif
 
+/*
+ * Print a continuation message with level. In case the continuation is split
+ * from the main message it preserves the level.
+ */
+
+#define pr_emerg_cont(fmt, ...)					\
+	printk(KERN_EMERG KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_alert_cont(fmt, ...)					\
+	printk(KERN_ALERT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_crit_cont(fmt, ...)					\
+	printk(KERN_CRIT KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_err_cont(fmt, ...)					\
+	printk(KERN_ERR KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_warn_cont(fmt, ...)					\
+	printk(KERN_WARN KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_notice_cont(fmt, ...)					\
+	printk(KERN_NOTICE KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_info_cont(fmt, ...)					\
+	printk(KERN_INFO KERN_CONT pr_fmt(fmt), ##__VA_ARGS__)
+/* no pr_debug_ratelimited, it doesn't make sense with CONFIG_DYNAMIC_DEBUG. */
+
 extern const struct file_operations kmsg_fops;
 
 enum {
-- 
2.38.1