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

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 5 Aug 2008 12:52:32 -0700 Nye Liu <nyet@nyet.org> wrote:

> 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..0dd0a73 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -7,6 +7,12 @@
>  #include <linux/string.h>
>  #include <linux/syscalls.h>
>  
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +#include <linux/utime.h>
> +#include <linux/namei.h>
> +#include <linux/list.h>
> +#endif

It would be better to do it unconditionally if possible - remove the
config option and all the ifdefs.

>  static __initdata char *message;
>  static void __init error(char *x)
>  {
> @@ -72,6 +78,38 @@ static void __init free_hash(void)
>  	}
>  }
>  
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +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);

kmalloc() can fail..

> +	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;
> +#endif
> +
>  /* cpio header parsing */
>  
>  static __initdata unsigned long ino, major, minor, nlink;
> @@ -97,6 +135,9 @@ static void __init parse_header(char *s)
>  	uid = parsed[2];
>  	gid = parsed[3];
>  	nlink = parsed[4];
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +	mtime.actime = mtime.modtime = parsed[5];
> +#endif
>  	body_len = parsed[6];
>  	major = parsed[7];
>  	minor = parsed[8];
> @@ -130,6 +171,10 @@ static inline void __init eat(unsigned n)
>  	count -= n;
>  }
>  
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +static __initdata char *vcollected;
> +#endif
> +
>  static __initdata char *collected;
>  static __initdata int remains;
>  static __initdata char *collect;
> @@ -271,6 +316,9 @@ static int __init do_name(void)
>  			if (wfd >= 0) {
>  				sys_fchown(wfd, uid, gid);
>  				sys_fchmod(wfd, mode);
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +				vcollected = kstrdup(collected, GFP_KERNEL);
> +#endif
>  				state = CopyFile;
>  			}
>  		}
> @@ -278,12 +326,18 @@ static int __init do_name(void)
>  		sys_mkdir(collected, mode);
>  		sys_chown(collected, uid, gid);
>  		sys_chmod(collected, mode);
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +		dir_add(collected, mtime);
> +#endif
>  	} 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);
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +			sys_utime(collected, &mtime);
> +#endif
>  		}
>  	}
>  	return 0;
> @@ -294,6 +348,10 @@ static int __init do_copy(void)
>  	if (count >= body_len) {
>  		sys_write(wfd, victim, body_len);
>  		sys_close(wfd);
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +		sys_utime(vcollected, &mtime);
> +		kfree(vcollected);
> +#endif
>  		eat(body_len);
>  		state = SkipIt;
>  		return 0;
> @@ -305,12 +363,48 @@ static int __init do_copy(void)
>  	}
>  }
>  
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +static long __init sys_lutime(char __user * filename,
> +	struct utimbuf __user * times)

Please avoid using the sys_ namespace.    That is for system calls.

Please pass the patch through scripts/checkpatch.pl and review the report.

> +{
> +	int error;
> +	struct path path;
> +	struct inode * inode;
> +	struct iattr newattrs;
> +
> +	error = user_lpath(filename, &path);
> +	if (error) return error;
> +
> +	inode = path.dentry->d_inode;
> +
> +	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
> +	error = 0;
> +	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
> +		goto pput_and_out;
> +
> +	newattrs.ia_atime.tv_sec = times->actime;
> +	newattrs.ia_atime.tv_nsec = 0;
> +	newattrs.ia_mtime.tv_sec = times->modtime;
> +	newattrs.ia_mtime.tv_nsec = 0;
> +	newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
> +	mutex_lock(&inode->i_mutex);
> +	error = notify_change(path.dentry, &newattrs);
> +	mutex_unlock(&inode->i_mutex);
> +pput_and_out:
> +	path_put(&path);
> +	return error;
> +}

How does this differ from sys_utime()?

Can this use do_utimes()?

> +#endif
> +
>  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);
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +	sys_lutime(collected, &mtime);
> +#endif
>  	state = SkipIt;
>  	next_state = Reset;
>  	return 0;
> @@ -466,6 +560,9 @@ static char * __init unpack_to_rootfs(char *buf, unsigned len, int check_only)
>  		buf += inptr;
>  		len -= inptr;
>  	}
> +#ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
> +	dir_utime();
> +#endif
>  	kfree(window);
>  	kfree(name_buf);
>  	kfree(symlink_buf);
> diff --git a/usr/Kconfig b/usr/Kconfig
> index 86cecb5..f7d9f60 100644
> --- a/usr/Kconfig
> +++ b/usr/Kconfig
> @@ -44,3 +44,13 @@ config INITRAMFS_ROOT_GID
>  	  owned by group root in the initial ramdisk image.
>  
>  	  If you are not sure, leave it set to "0".
> +
> +config INITRAMFS_PRESERVE_MTIME
> +	bool "Preserve mtimes from INITRAMFS image"
> +	depends on BLK_DEV_INITRD
> +	default n
> +	help
> +	  Preserve mtimes (last modified times) for all items stored in the
> +	  initramfs image.
> +
> +	  If you are not sure, leave it set to "N"