linux-kernel - [PATCH 3/4] printk/btrfs: Handle more message headers

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Date:   Thu, 27 Oct 2016 17:52:53 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Joe Perches <joe@...ches.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <jbacik@...com>, David Sterba <dsterba@...e.com>,
        linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>
Subject: [PATCH 3/4] printk/btrfs: Handle more message headers

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.

Note that 3 bytes should be enough for the header buffer. I am not
sure where the 4 bytes came from. Maybe it expected that both
KERN_SOH and the log level strings end with '\0' but they
are concatenated.

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@...e.com>
---
 fs/btrfs/super.c | 28 +++++++++++++++-------------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 74ed5aae6cea..2d836c676895 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -202,27 +202,29 @@ 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[3];
 	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) {
-		size_t size = printk_skip_level(fmt) - fmt;
-		memcpy(lvl, fmt,  size);
-		lvl[size] = '\0';
-		fmt += size;
-		type = logtypes[kern_level - '0'];
-		ratelimit = &printk_limits[kern_level - '0'];
-	} else {
+	while ((kern_level = printk_get_level(fmt)) != 0) {
+		if (kern_level >= '0' || kern_level <= '7') {
+			memcpy(lvl, fmt,  2);
+			lvl[2] = '\0';
+			type = logtypes[kern_level - '0'];
+			ratelimit = &printk_limits[kern_level - '0'];
+		}
+		fmt += 2;
+	}
+
+	if (!type) {
 		*lvl = '\0';
-		/* Default to debug output */
-		ratelimit = &printk_limits[7];
+		type = logtypes[4];
+		ratelimit = &printk_limits[4];
 	}
 
 	vaf.fmt = fmt;
-- 
1.8.5.6