[PATCH] INITRAMFS: Add option to preserve mtime from INITRAMFS cpio images

[Nye Liu <nyet@nyet.org>]

Resubmission of initramfs preserve mtime patch following Andrew Morton's
suggestions.

From: Nye Liu <nyet@nyet.org>

When unpacking the cpio into the initramfs, mtimes are not preserved by
default. This patch adds an INITRAMFS_PRESERVE_MTIME option that allows mtimes
stored in the cpio image to be used when constructing the initramfs. For
embedded applications that run exclusively out of the initramfs, this is
invaluable.

Signed-off-by: Nye Liu <nyet@nyet.org>

diff --git a/init/initramfs.c b/init/initramfs.c
index 644fc01..ebfc049 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -6,6 +6,7 @@
 #include <linux/delay.h>
 #include <linux/string.h>
 #include <linux/syscalls.h>
+#include <linux/utime.h>
 
 static __initdata char *message;
 static void __init error(char *x)
@@ -72,6 +73,38 @@ static void __init free_hash(void)
 	}
 }
 
+static __initdata LIST_HEAD(dir_list);
+struct dir_entry {
+	struct list_head list;
+	char *name;
+	struct utimbuf mtime;
+};
+
+static void __init dir_add(const char *name, struct utimbuf mtime)
+{
+	struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
+	if (!de)
+		panic("can't allocate dir_entry buffer");
+	INIT_LIST_HEAD(&de->list);
+	de->name = kstrdup(name, GFP_KERNEL);
+	de->mtime = mtime;
+	list_add(&de->list, &dir_list);
+}
+
+static void __init dir_utime(void)
+{
+	struct list_head *e, *tmp;
+	list_for_each_safe(e, tmp, &dir_list) {
+		struct dir_entry *de = list_entry(e, struct dir_entry, list);
+		list_del(e);
+		sys_utime(de->name, &de->mtime);
+		kfree(de->name);
+		kfree(de);
+	}
+}
+
+static __initdata struct utimbuf mtime;
+
 /* cpio header parsing */
 
 static __initdata unsigned long ino, major, minor, nlink;
@@ -97,6 +130,7 @@ static void __init parse_header(char *s)
 	uid = parsed[2];
 	gid = parsed[3];
 	nlink = parsed[4];
+	mtime.actime = mtime.modtime = parsed[5];
 	body_len = parsed[6];
 	major = parsed[7];
 	minor = parsed[8];
@@ -130,6 +164,7 @@ static inline void __init eat(unsigned n)
 	count -= n;
 }
 
+static __initdata char *vcollected;
 static __initdata char *collected;
 static __initdata int remains;
 static __initdata char *collect;
@@ -271,6 +306,7 @@ static int __init do_name(void)
 			if (wfd >= 0) {
 				sys_fchown(wfd, uid, gid);
 				sys_fchmod(wfd, mode);
+				vcollected = kstrdup(collected, GFP_KERNEL);
 				state = CopyFile;
 			}
 		}
@@ -278,12 +314,14 @@ static int __init do_name(void)
 		sys_mkdir(collected, mode);
 		sys_chown(collected, uid, gid);
 		sys_chmod(collected, mode);
+		dir_add(collected, mtime);
 	} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
 		   S_ISFIFO(mode) || S_ISSOCK(mode)) {
 		if (maybe_link() == 0) {
 			sys_mknod(collected, mode, rdev);
 			sys_chown(collected, uid, gid);
 			sys_chmod(collected, mode);
+			sys_utime(collected, &mtime);
 		}
 	}
 	return 0;
@@ -294,6 +332,8 @@ static int __init do_copy(void)
 	if (count >= body_len) {
 		sys_write(wfd, victim, body_len);
 		sys_close(wfd);
+		sys_utime(vcollected, &mtime);
+		kfree(vcollected);
 		eat(body_len);
 		state = SkipIt;
 		return 0;
@@ -305,12 +345,26 @@ static int __init do_copy(void)
 	}
 }
 
+static long __init do_lutime(char __user *filename,
+	struct utimbuf __user *times)
+{
+	struct timespec t[2];
+
+	t[0].tv_sec = times->actime;
+	t[0].tv_nsec = 0;
+	t[1].tv_sec = times->modtime;
+	t[1].tv_nsec = 0;
+
+	return do_utimes(AT_FDCWD, filename, t, AT_SYMLINK_NOFOLLOW);
+}
+
 static int __init do_symlink(void)
 {
 	collected[N_ALIGN(name_len) + body_len] = '\0';
 	clean_path(collected, 0);
 	sys_symlink(collected + N_ALIGN(name_len), collected);
 	sys_lchown(collected, uid, gid);
+	do_lutime(collected, &mtime);
 	state = SkipIt;
 	next_state = Reset;
 	return 0;
@@ -466,6 +520,7 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len, int check_only)
 		buf += inptr;
 		len -= inptr;
 	}
+	dir_utime();
 	kfree(window);
 	kfree(name_buf);
 	kfree(symlink_buf);