[PATCH 1/2] Populate rootfs asynchronously for boot performance

[Surbhi Palande]

populate_rootfs() is called asynchronously to reduce the boot time.

Signed-off-by: Surbhi Palande <surbhi.palande at canonical.com>
---
 init/initramfs.c |   15 ++++++++++++---
 init/main.c      |    7 +++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index 4c00edc..aad2c28 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -8,6 +8,7 @@
 #include <linux/dirent.h>
 #include <linux/syscalls.h>
 #include <linux/utime.h>
+#include <linux/async.h>
 
 static __initdata char *message;
 static void __init error(char *x)
@@ -565,7 +566,9 @@ static void __init clean_rootfs(void)
 }
 #endif
 
-static int __init populate_rootfs(void)
+extern struct list_head rootfs_fn_list;
+
+static void __init async_populate_rootfs(void)
 {
 	char *err = unpack_to_rootfs(__initramfs_start,
 			 __initramfs_end - __initramfs_start);
@@ -579,7 +582,7 @@ static int __init populate_rootfs(void)
 			initrd_end - initrd_start);
 		if (!err) {
 			free_initrd();
-			return 0;
+			return;
 		} else {
 			clean_rootfs();
 			unpack_to_rootfs(__initramfs_start,
@@ -603,6 +606,12 @@ static int __init populate_rootfs(void)
 		free_initrd();
 #endif
 	}
-	return 0;
+	return;
 }
+
+static int __init populate_rootfs(void)
+{
+	async_schedule_domain(async_populate_rootfs, NULL, &rootfs_fn_list);
+}
+
 rootfs_initcall(populate_rootfs);
diff --git a/init/main.c b/init/main.c
index 4051d75..d40ca6f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -752,6 +752,7 @@ int do_one_initcall(initcall_t fn)
 
 
 extern initcall_t __initcall_start[], __initcall_end[], __early_initcall_end[];
+LIST_HEAD(rootfs_fn_list);
 
 static void __init do_initcalls(void)
 {
@@ -879,6 +880,12 @@ static int __init kernel_init(void * unused)
 	do_basic_setup();
 
 	/*
+	 * putting it here to ensure that rootfs is populated by the end of
+	 * this call
+	 */
+	async_synchronize_full_domain(&rootfs_fn_list);
+
+	/*
 	 * check if there is an early userspace init.  If yes, let it do all
 	 * the work
 	 */
-- 
1.6.3.3