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Message-ID: <20080903225459.GB9893@mrv.com>
Date: Wed, 3 Sep 2008 15:54:59 -0700
From: Nye Liu <nyet@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Nye Liu <nyet@...t.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] INITRAMFS: Add option to preserve mtime from INITRAMFS
cpio images
On Wed, Sep 03, 2008 at 03:48:40PM -0700, Andrew Morton wrote:
> On Wed, 3 Sep 2008 15:41:31 -0700
> Nye Liu <nyet@...t.org> wrote:
>
> > > > 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();
> > >
> > > Perhaps this is the simplest implementation - I didn't check the fine
> > > details. What's your thinking here?
> > >
> >
> > The main problem is that i need to save off the entire list for later
> > processing of the directory mtimes... if i process the directory mtimes
> > in the same pass as the file/link mtimes, touching the directory inode
> > when creating/modifying the file/links updates the directory mtime, and
> > overwrites whatever mtime i set the directory to when i created it.
> >
> > The only solution is to do a two pass, which is why the list is
> > necessary. If there is a better way, i did not find it :(
> >
> > It could be that i misunderstood your question though :)
>
> I'm wondering whether this code need to use `struct utimbuf' at all.
> Or at least, as much as it does. utimbuf is more a userspace-facing
> thing whereas in-kernel timespecs and timevals are more common.
>
> The code as you have it does a fair few conversions into utimbuf format
> (both directly and via the existing functions which it calls). Would
> it be simpler if it dealt in terms of timespecs?
>
maybe something like this:
diff --git a/init/initramfs.c b/init/initramfs.c
index 644fc01..89d3e53 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 +73,45 @@ static void __init free_hash(void)
}
}
+static __initdata LIST_HEAD(dir_list);
+struct dir_entry {
+ struct list_head list;
+ char *name;
+ time_t mtime;
+};
+
+static void __init dir_add(const char *name, time_t 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 do_utime(char *name, time_t mtime)
+{
+ struct utimbuf time;
+ time.actime=time.modtime=mtime;
+ sys_utime(name, &time);
+}
+
+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);
+ do_utime(de->name, de->mtime);
+ kfree(de->name);
+ kfree(de);
+ }
+}
+
+static __initdata time_t mtime;
+
/* cpio header parsing */
static __initdata unsigned long ino, major, minor, nlink;
@@ -97,6 +137,7 @@ static void __init parse_header(char *s)
uid = parsed[2];
gid = parsed[3];
nlink = parsed[4];
+ mtime = parsed[5];
body_len = parsed[6];
major = parsed[7];
minor = parsed[8];
@@ -130,6 +171,7 @@ 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 +313,7 @@ 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 +321,14 @@ 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);
+ do_utime(collected, mtime);
}
}
return 0;
@@ -294,6 +339,8 @@ static int __init do_copy(void)
if (count >= body_len) {
sys_write(wfd, victim, body_len);
sys_close(wfd);
+ do_utime(vcollected, mtime);
+ kfree(vcollected);
eat(body_len);
state = SkipIt;
return 0;
@@ -305,12 +352,26 @@ static int __init do_copy(void)
}
}
+static long __init do_lutime(char __user *filename,
+ time_t mtime)
+{
+ struct timespec t[2];
+
+ t[0].tv_sec = mtime;
+ t[0].tv_nsec = 0;
+ t[1].tv_sec = mtime;
+ 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 +527,7 @@ 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);
--
Nye Liu
nliu@....com
(818) 772-6235x248
(818) 772-0576 fax
"Who would be stupid enough to quote a fictitious character?"
-- Don Quixote
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