printk: allocate kernel log buffer earlier

On larger systems, because of the numerous ACPI, Bootmem and EFI messages,
the static log buffer overflows before the larger one specified by the
log_buf_len param is allocated.  Minimize the overflow by allocating the
new log buffer as soon as possible.

On kernels without memblock, a later call to setup_log_buf from
kernel/init.c is the fallback.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix CONFIG_PRINTK=n build]
Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 58 insertions, 29 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index da8ca817eae3..35185392173f 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -31,6 +31,7 @@
 #include <linux/smp.h>
 #include <linux/security.h>
 #include <linux/bootmem.h>
+#include <linux/memblock.h>
 #include <linux/syscalls.h>
 #include <linux/kexec.h>
 #include <linux/kdb.h>
@@ -167,46 +168,74 @@ void log_buf_kexec_setup(void)
 }
 #endif
 
+/* requested log_buf_len from kernel cmdline */
+static unsigned long __initdata new_log_buf_len;
+
+/* save requested log_buf_len since it's too early to process it */
 static int __init log_buf_len_setup(char *str)
 {
         unsigned size = memparse(str, &str);
-        unsigned long flags;
 
         if (size)
                 size = roundup_pow_of_two(size);
-        if (size > log_buf_len) {
-                unsigned start, dest_idx, offset;
-                char *new_log_buf;
+        if (size > log_buf_len)
+                new_log_buf_len = size;
 
-                new_log_buf = alloc_bootmem(size);
-                if (!new_log_buf) {
-                        printk(KERN_WARNING "log_buf_len: allocation failed\n");
-                        goto out;
-                }
+        return 0;
+}
+early_param("log_buf_len", log_buf_len_setup);
 
-                spin_lock_irqsave(&logbuf_lock, flags);
-                log_buf_len = size;
-                log_buf = new_log_buf;
-
-                offset = start = min(con_start, log_start);
-                dest_idx = 0;
-                while (start != log_end) {
-                        log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
-                        start++;
-                        dest_idx++;
-                }
-                log_start -= offset;
-                con_start -= offset;
-                log_end -= offset;
-                spin_unlock_irqrestore(&logbuf_lock, flags);
+void __init setup_log_buf(int early)
+{
+        unsigned long flags;
+        unsigned start, dest_idx, offset;
+        char *new_log_buf;
+        int free;
+
+        if (!new_log_buf_len)
+                return;
+
+        if (early) {
+                unsigned long mem;
 
-                printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
+                mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
+                if (mem == MEMBLOCK_ERROR)
+                        return;
+                new_log_buf = __va(mem);
+        } else {
+                new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
         }
-out:
-        return 1;
-}
 
-__setup("log_buf_len=", log_buf_len_setup);
+        if (unlikely(!new_log_buf)) {
+                pr_err("log_buf_len: %ld bytes not available\n",
+                        new_log_buf_len);
+                return;
+        }
+
+        spin_lock_irqsave(&logbuf_lock, flags);
+        log_buf_len = new_log_buf_len;
+        log_buf = new_log_buf;
+        new_log_buf_len = 0;
+        free = __LOG_BUF_LEN - log_end;
+
+        offset = start = min(con_start, log_start);
+        dest_idx = 0;
+        while (start != log_end) {
+                unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1);
+
+                log_buf[dest_idx] = __log_buf[log_idx_mask];
+                start++;
+                dest_idx++;
+        }
+        log_start -= offset;
+        con_start -= offset;
+        log_end -= offset;
+        spin_unlock_irqrestore(&logbuf_lock, flags);
+
+        pr_info("log_buf_len: %d\n", log_buf_len);
+        pr_info("early log buf free: %d(%d%%)\n",
+                free, (free * 100) / __LOG_BUF_LEN);
+}
 
 #ifdef CONFIG_BOOT_PRINTK_DELAY