On 11/27/2018 07:34 AM, Andrew Morton wrote:
On Fri, 16 Nov 2018 15:12:48 +0800 Li Zhijian <lizhij...@cn.fujitsu.com> wrote:
Previously, sys_link() will fail due to the new path is already existed.
this case ofen appears when we use a concated initrd, below is an
sample:
1) prepare a basic rootfs, it contains a regular files rc.local
lizhijian@:~/yocto-tiny-i386-2016-04-22$ cat etc/rc.local
#!/bin/sh
echo "Running /etc/rc.local..."
yocto-tiny-i386-2016-04-22$ find . | sed 's,^\./,,' | cpio -o -H newc | gzip -n -9
>../rootfs.cgz
2) create a extra initrd which also includes a etc/rc.local
lizhijian@:~/lkp-x86_64/etc$ echo "append initrd" >rc.local
lizhijian@:~/lkp/lkp-x86_64/etc$ cat rc.local
append initrd
lizhijian@:~/lkp/lkp-x86_64/etc$ ln rc.local rc.local.hardlink
append initrd
lizhijian@:~/lkp/lkp-x86_64/etc$ stat rc.local rc.local.hardlink
File: 'rc.local'
Size: 14 Blocks: 8 IO Block: 4096 regular file
Device: 801h/2049d Inode: 11296086 Links: 2
Access: (0664/-rw-rw-r--) Uid: ( 1002/lizhijian) Gid: ( 1002/lizhijian)
Access: 2018-11-15 16:08:28.654464815 +0800
Modify: 2018-11-15 16:07:57.514903210 +0800
Change: 2018-11-15 16:08:24.180228872 +0800
Birth: -
File: 'rc.local.hardlink'
Size: 14 Blocks: 8 IO Block: 4096 regular file
Device: 801h/2049d Inode: 11296086 Links: 2
Access: (0664/-rw-rw-r--) Uid: ( 1002/lizhijian) Gid: ( 1002/lizhijian)
Access: 2018-11-15 16:08:28.654464815 +0800
Modify: 2018-11-15 16:07:57.514903210 +0800
Change: 2018-11-15 16:08:24.180228872 +0800
Birth: -
lizhijian@:~/lkp/lkp-x86_64$ find . | sed 's,^\./,,' | cpio -o -H newc | gzip -n
-9 >../rc-local.cgz
lizhijian@:~/lkp/lkp-x86_64$ gzip -dc ../rc-local.cgz | cpio -t
.
etc
etc/rc.local.hardlink <<< it will be extracted first at this initrd
etc/rc.local
3) concate 2 initrds and boot
lizhijian@:~/lkp$ cat rootfs.cgz rc-local.cgz >concate-initrd.cgz
lizhijian@:~/lkp$ qemu-system-x86_64 -nographic -enable-kvm -cpu host -smp 1 -m 1024
-kernel ~/lkp/linux/arch/x86/boot/bzImage -append "console=ttyS0 earlyprint=ttyS0
ignore_loglevel" -initrd ./concate-initr.cgz -serial stdio -nodefaults
In this case, sys_link(2) will fail and return -EEXIST, so we can only
get the rc.local at rootfs.cgz instead of rc-local.cgz
I can't claim to understand this, but I believe you ;)
thank you.
IMO, people who use concatenated initrd(cat rootfs.cgz rc-local.cgz
>concatenated-initrd.cgz),
could expect that the later initrd(rc-local.cgz) can overwrite the previous
initrd(rootfs.cgz).
However the previous kernel can not ensure this.
How serious is this problem? Do you think a 4.20 merge is justified?
It's critical for our scenario where it always concatenates multiple initrds.
and our scenario often use the latest kernel, so 4.20+ is good to us.
Or a -stable backport? If so, why?
The forward declaration is unpleasing. Why not simply move the function?
Got it, i will update in V2
Thanks
--- a/init/initramfs.c~initramfs-clean-old-path-before-creating-a-hardlink-fix
+++ a/init/initramfs.c
@@ -291,7 +291,17 @@ static int __init do_reset(void)
return 1;
}
-static void __init clean_path(char *path, umode_t fmode);
+static void __init clean_path(char *path, umode_t fmode)
+{
+ struct kstat st;
+
+ if (!vfs_lstat(path, &st) && (st.mode ^ fmode) & S_IFMT) {
+ if (S_ISDIR(st.mode))
+ ksys_rmdir(path);
+ else
+ ksys_unlink(path);
+ }
+}
static int __init maybe_link(void)
{
@@ -305,18 +315,6 @@ static int __init maybe_link(void)
return 0;
}
-static void __init clean_path(char *path, umode_t fmode)
-{
- struct kstat st;
-
- if (!vfs_lstat(path, &st) && (st.mode ^ fmode) & S_IFMT) {
- if (S_ISDIR(st.mode))
- ksys_rmdir(path);
- else
- ksys_unlink(path);
- }
-}
-
static __initdata int wfd;
static int __init do_name(void)
_
.
