• Li Zhijian's avatar
    initramfs: clean old path before creating a hardlink · 7c0950d4
    Li Zhijian authored
    sys_link() can fail due to the new path already existing.  This case
    ofen occurs when we use a concated initrd, for example:
    
    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
    
    [akpm@linux-foundation.org: move code to avoid forward declaration]
    Link: http://lkml.kernel.org/r/1542352368-13299-1-git-send-email-lizhijian@cn.fujitsu.comSigned-off-by: 's avatarLi Zhijian <lizhijian@cn.fujitsu.com>
    Cc: Philip Li <philip.li@intel.com>
    Cc: Dominik Brodowski <linux@dominikbrodowski.net>
    Cc: Li Zhijian <zhijianx.li@intel.com>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    7c0950d4
initramfs.c 13.8 KB