initramfs: factor out a helper to populate the initrd image

This will allow for cleaner code sharing in the caller.

Link: http://lkml.kernel.org/r/20190213174621.29297-5-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>	[arm64]
Cc: Geert Uytterhoeven <geert@linux-m68k.org>	[m68k]
Cc: Steven Price <steven.price@arm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/initramfs.c

@@ -597,6 +597,28 @@ static void __init clean_rootfs(void)
 }
 #endif
 
+#ifdef CONFIG_BLK_DEV_RAM
+static void populate_initrd_image(char *err)
+{
+	ssize_t written;
+	int fd;
+
+	unpack_to_rootfs(__initramfs_start, __initramfs_size);
+
+	printk(KERN_INFO "rootfs image is not initramfs (%s); looks like an initrd\n",
+			err);
+	fd = ksys_open("/initrd.image", O_WRONLY | O_CREAT, 0700);
+	if (fd < 0)
+		return;
+
+	written = xwrite(fd, (char *)initrd_start, initrd_end - initrd_start);
+	if (written != initrd_end - initrd_start)
+		pr_err("/initrd.image: incomplete write (%zd != %ld)\n",
+		       written, initrd_end - initrd_start);
+	ksys_close(fd);
+}
+#endif /* CONFIG_BLK_DEV_RAM */
+
 static int __init populate_rootfs(void)
 {
 	/* Load the built in initramfs */
@@ -606,7 +628,6 @@ static int __init populate_rootfs(void)
 	/* If available load the bootloader supplied initrd */
 	if (initrd_start && !IS_ENABLED(CONFIG_INITRAMFS_FORCE)) {
 #ifdef CONFIG_BLK_DEV_RAM
-		int fd;
 		printk(KERN_INFO "Trying to unpack rootfs image as initramfs...\n");
 		err = unpack_to_rootfs((char *)initrd_start,
 			initrd_end - initrd_start);
@@ -614,22 +635,7 @@ static int __init populate_rootfs(void)
 			goto done;
 
 		clean_rootfs();
-		unpack_to_rootfs(__initramfs_start, __initramfs_size);
-
-		printk(KERN_INFO "rootfs image is not initramfs (%s)"
-				"; looks like an initrd\n", err);
-		fd = ksys_open("/initrd.image",
-			      O_WRONLY|O_CREAT, 0700);
-		if (fd >= 0) {
-			ssize_t written = xwrite(fd, (char *)initrd_start,
-						initrd_end - initrd_start);
-
-			if (written != initrd_end - initrd_start)
-				pr_err("/initrd.image: incomplete write (%zd != %ld)\n",
-				       written, initrd_end - initrd_start);
-
-			ksys_close(fd);
-		}
+		populate_initrd_image(err);
 	done:
 		/* empty statement */;
 #else