kernel/printk: use on-stack allocations for kernel log

These allocationsare just 1kb in size, using kmalloc is not
worth it for them. This should speed up printing of kernel log
when uptime gets very long.

Signed-off-by: Yaroslav Furman <yaro330@gmail.com>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 56b2415..030e4e9 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1158,13 +1158,11 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
 
 static int syslog_print(char __user *buf, int size)
 {
-       char *text;
+       char text[LOG_LINE_MAX + PREFIX_MAX];
        struct printk_log *msg;
        int len = 0;
 
-       text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
-       if (!text)
-               return -ENOMEM;
+       memset(&text, 0, LOG_LINE_MAX + PREFIX_MAX);
 
        while (size > 0) {
                size_t n;
@@ -1216,18 +1214,15 @@ static int syslog_print(char __user *buf, int size)
                buf += n;
        }
 
-       kfree(text);
        return len;
 }
 
 static int syslog_print_all(char __user *buf, int size, bool clear)
 {
-       char *text;
+       char text[LOG_LINE_MAX + PREFIX_MAX];
        int len = 0;
 
-       text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
-       if (!text)
-               return -ENOMEM;
+       memset(&text, 0, LOG_LINE_MAX + PREFIX_MAX);
 
        raw_spin_lock_irq(&logbuf_lock);
        if (buf) {
@@ -1311,7 +1306,6 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
        }
        raw_spin_unlock_irq(&logbuf_lock);
 
-       kfree(text);
        return len;
 }