[PATCH v2 3/4] printk/btrfs: Handle more message headers

[Petr Mladek <pmladek@suse.com>]

The commit 4bcc595ccd80decb4245096e ("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 04d2c8c83d0e3ac5f ("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.

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
 fs/btrfs/super.c       | 26 +++++++++++++++-----------
 include/linux/printk.h |  2 ++
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 74ed5aae6cea..c083d84eaa32 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -202,27 +202,31 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
 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;
diff --git a/include/linux/printk.h b/include/linux/printk.h
index a0859e169bc3..afe8ccec1672 100644
--- a/include/linux/printk.h
+++ b/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]) {
-- 
1.8.5.6