printk/btrfs: handle more message headers

Commit 4bcc595 ("printk: reinstate KERN_CONT for printing
continuation lines") allows to define more message headers for a single
message.  The motivation is that continuous lines might get mixed.
Therefore it make sense to define the right log level for every piece of
a cont line.

The current btrfs_printk() macros do not support continuous lines at the
moment.  But better be prepared for a custom messages and avoid
potential "lvl" buffer overflow.

This patch iterates over the entire message header.  It is interested
only into the message level like the original code.

This patch also introduces PRINTK_MAX_SINGLE_HEADER_LEN.  Three bytes
are enough for the message level header at the moment.  But it used to
be three, see the commit 04d2c8c ("printk: convert the format for
KERN_<LEVEL> to a 2 byte pattern").

Also I fixed the default ratelimit level.  It looked very strange when it
was different from the default log level.

[[email protected]: Fix a check of the valid message level]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>
Acked-by: David Sterba <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Jason Wessel <[email protected]>
Cc: Jaroslav Kysela <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Josef Bacik <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/btrfs/super.c

@@ -202,27 +202,31 @@ static struct ratelimit_state printk_limits[] = {
 void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 {
 	struct super_block *sb = fs_info->sb;
-	char lvl[4];
+	char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1];
 	struct va_format vaf;
 	va_list args;
-	const char *type = logtypes[4];
+	const char *type = NULL;
 	int kern_level;
 	struct ratelimit_state *ratelimit;
 
 	va_start(args, fmt);
 
-	kern_level = printk_get_level(fmt);
-	if (kern_level) {
+	while ((kern_level = printk_get_level(fmt)) != 0) {
 		size_t size = printk_skip_level(fmt) - fmt;
-		memcpy(lvl, fmt,  size);
-		lvl[size] = '\0';
+
+		if (kern_level >= '0' && kern_level <= '7') {
+			memcpy(lvl, fmt,  size);
+			lvl[size] = '\0';
+			type = logtypes[kern_level - '0'];
+			ratelimit = &printk_limits[kern_level - '0'];
+		}
 		fmt += size;
-		type = logtypes[kern_level - '0'];
-		ratelimit = &printk_limits[kern_level - '0'];
-	} else {
+	}
+
+	if (!type) {
 		*lvl = '\0';
-		/* Default to debug output */
-		ratelimit = &printk_limits[7];
+		type = logtypes[4];
+		ratelimit = &printk_limits[4];
 	}
 
 	vaf.fmt = fmt;

include/linux/printk.h

@@ -10,6 +10,8 @@
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
 
+#define PRINTK_MAX_SINGLE_HEADER_LEN 2
+
 static inline int printk_get_level(const char *buffer)
 {
 	if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {