linux-kernel - [patch]fastboot: remove duplicate unpack_to

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Date:	Wed, 13 Aug 2008 14:07:49 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>
Subject: [patch]fastboot: remove duplicate unpack_to_rootfs()

we check if initrd is initramfs first and then do real unpack. The check
isn't required, we can directly do unpack. If initrd isn't initramfs, we
can remove garbage. In my laptop, this saves 0.1s boot time. This
penalizes non-initramfs case, but now initramfs is mostly widely used.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>

diff --git a/init/initramfs.c b/init/initramfs.c
index 644fc01..e51c92b 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -5,6 +5,7 @@
 #include <linux/fcntl.h>
 #include <linux/delay.h>
 #include <linux/string.h>
+#include <linux/dirent.h>
 #include <linux/syscalls.h>
 
 static __initdata char *message;
@@ -520,6 +521,37 @@ skip:
 	initrd_end = 0;
 }
 
+static void __init clean_rootfs(void)
+{
+	int fd = sys_open("/", O_RDONLY, 0);
+	void *buf = malloc(1024);
+	struct linux_dirent64 *dirp = buf;
+	int count;
+
+	memset(buf, 0, PAGE_SIZE);
+	count = sys_getdents64(fd, dirp, PAGE_SIZE);
+	while (count > 0) {
+		while (count > 0) {
+			struct stat st;
+
+			sys_newlstat(dirp->d_name, &st);
+			if (S_ISDIR(st.st_mode))
+				sys_rmdir(dirp->d_name);
+			else
+				sys_unlink(dirp->d_name);
+
+			count -= dirp->d_reclen;
+			dirp = (void *)dirp + dirp->d_reclen;
+		}
+		dirp = buf;
+		memset(buf, 0, 1024);
+		count = sys_getdents64(fd, dirp, PAGE_SIZE);
+	}
+
+	sys_close(fd);
+	free(buf);
+}
+
 static int __init populate_rootfs(void)
 {
 	char *err = unpack_to_rootfs(__initramfs_start,
@@ -531,13 +563,15 @@ static int __init populate_rootfs(void)
 		int fd;
 		printk(KERN_INFO "checking if image is initramfs...");
 		err = unpack_to_rootfs((char *)initrd_start,
-			initrd_end - initrd_start, 1);
+			initrd_end - initrd_start, 0);
 		if (!err) {
 			printk(" it is\n");
-			unpack_to_rootfs((char *)initrd_start,
-				initrd_end - initrd_start, 0);
 			free_initrd();
 			return 0;
+		} else {
+			clean_rootfs();
+			unpack_to_rootfs(__initramfs_start,
+				 __initramfs_end - __initramfs_start, 0);
 		}
 		printk("it isn't (%s); looks like an initrd\n", err);
 		fd = sys_open("/initrd.image", O_WRONLY|O_CREAT, 0700);


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