linux-kernel - [PATCH 1/5] printk: Split code for making free space in the log buffer

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Date:	Thu, 10 Apr 2014 11:43:12 +0200
From:	Petr Mladek <pmladek@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jan Kara <jack@...e.cz>, Jiri Kosina <jkosina@...e.cz>,
	Kay Sievers <kay@...y.org>, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.cz>
Subject: [PATCH 1/5] printk: Split code for making free space in the log buffer

There will be needed some fixes in the check for free space. They will
be easier if the code is moved outside of the quite long log_store()
function.

This patch does not change the existing behavior.

Signed-off-by: Petr Mladek <pmladek@...e.cz>
---
 kernel/printk/printk.c | 44 +++++++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 15 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a45b50962295..cc7d7defce24 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -297,6 +297,34 @@ static u32 log_next(u32 idx)
 	return idx + msg->len;
 }
 
+/* check whether there is enough free space for the given message */
+static int logbuf_has_space(u32 msg_size)
+{
+	u32 free;
+
+	if (log_next_idx > log_first_idx)
+		free = max(log_buf_len - log_next_idx, log_first_idx);
+	else
+		free = log_first_idx - log_next_idx;
+
+	/*
+	 * We need space also for an empty header that signalizes wrapping
+	 * of the buffer.
+	 */
+	return free >= msg_size + sizeof(struct printk_log);
+}
+
+static void log_make_free_space(u32 msg_size)
+{
+	while (log_first_seq < log_next_seq) {
+		if (logbuf_has_space(msg_size))
+			return;
+		/* drop old messages until we have enough continuous space */
+		log_first_idx = log_next(log_first_idx);
+		log_first_seq++;
+	}
+}
+
 /* insert record into the buffer, discard old ones, update heads */
 static void log_store(int facility, int level,
 		      enum log_flags flags, u64 ts_nsec,
@@ -311,21 +339,7 @@ static void log_store(int facility, int level,
 	pad_len = (-size) & (LOG_ALIGN - 1);
 	size += pad_len;
 
-	while (log_first_seq < log_next_seq) {
-		u32 free;
-
-		if (log_next_idx > log_first_idx)
-			free = max(log_buf_len - log_next_idx, log_first_idx);
-		else
-			free = log_first_idx - log_next_idx;
-
-		if (free >= size + sizeof(struct printk_log))
-			break;
-
-		/* drop old messages until we have enough contiuous space */
-		log_first_idx = log_next(log_first_idx);
-		log_first_seq++;
-	}
+	log_make_free_space(size);
 
 	if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
 		/*
-- 
1.8.4

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