Hi,
When verified some patches on linux-next branch I found Debian rootfs cannot be mounted successfully on Hikey, the booting log is: http://termbin.com/akar
From the log, we can see:
mount: mounting udev on /dev failed: Device or resource busy ... ALERT! /dev/disk/by-partlabel/system does not exist. Dropping to a shell!
So I bisected the linux-next branch and narrow down below patch which introduces mounting failure; after applied this patch, the kernel will mount devtmpfs on '/dev', then later udev cannot mount again for devfs. Finally cannot find '/dev/disk/by-partlabel/system' for rootfs.
I don't know what's the best way to fix this issue, welcome any suggestion for this. And report this issue in case it may impact later Debian release?
Thanks, Leo Yan
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From ee35011fd0324b37fbb046561e58d4d6bae798ac Mon Sep 17 00:00:00 2001
From: Rob Landley rob@landley.net Date: Fri, 19 May 2017 07:39:23 +1000 Subject: [PATCH] initramfs: make initramfs honor CONFIG_DEVTMPFS_MOUNT
Make initramfs honor CONFIG_DEVTMPFS_MOUNT, fixing 2b2af54a5bb6 ("Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev"), which didn't bother. Move /dev/console open after devtmpfs mount, and update help text.
Commit 456eeabab849 in 2005 made gen_initramfs_list (when run with no arguments) spit out an 'example' config creating /dev and /dev/console. The kernel accidentally(?) included this for many years when you didn't specify initramfs contents, and of course grew dependencies on this /dev/console node in the (often hidden) initramfs. c33df4eaaf41 ("disable init/initramfs.c") in 2007 explicitly preserved this dependency. 2bd3a997befc ("init: Open /dev/console from rootfs") in 2010 claimed it "removes the occasionally problematic assumption that /dev/console exists from the boot code" but actually just moved it later.
But nobody never tested statically linking an initramfs. If you point CONFIG_INITRAMFS_SOURCE at a directory running the build as a normal user you _don't_ get a /dev/console (because you can't create it without being root, and can't use the existing one out of /dev unless you create your own initramfs list file), in which case init runs with stdin/stdout/stderr closed and you get no output.
Eric's test case for his 2010 commit referenced above was:
With this patch I was able to throw busybox on my /boot partition (which has no /dev directory) and boot into userspace without problems.
But it didn't work pointing CONFIG_INITRAMFS_SOURCE at a directory of the same files. This provides the "automatically mounting devtmpfs on /dev" workaround the earlier commit was trying to avoid.
Link: http://lkml.kernel.org/r/21935caf-501d-e97c-5611-5c4af7e0f9ae@landley.net Signed-off-by: Rob Landley rob@landley.net Cc: Eric W. Biederman ebiederm@xmission.com Cc: Jean-Paul Saman jean-paul.saman@nxp.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Prarit Bhargava prarit@redhat.com Cc: Yang Shi yang.shi@linaro.org Cc: Rasmus Villemoes linux@rasmusvillemoes.dk Cc: Kees Cook keescook@chromium.org Cc: Emese Revfy re.emese@gmail.com Cc: Petr Mladek pmladek@suse.com Cc: Fabian Frederick fabf@skynet.be Signed-off-by: Andrew Morton akpm@linux-foundation.org --- drivers/base/Kconfig | 14 ++++---------- init/main.c | 15 +++++++++------ 2 files changed, 13 insertions(+), 16 deletions(-)
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index d718ae4..74779ee 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -48,16 +48,10 @@ config DEVTMPFS_MOUNT bool "Automount devtmpfs at /dev, after the kernel mounted the rootfs" depends on DEVTMPFS help - This will instruct the kernel to automatically mount the - devtmpfs filesystem at /dev, directly after the kernel has - mounted the root filesystem. The behavior can be overridden - with the commandline parameter: devtmpfs.mount=0|1. - This option does not affect initramfs based booting, here - the devtmpfs filesystem always needs to be mounted manually - after the rootfs is mounted. - With this option enabled, it allows to bring up a system in - rescue mode with init=/bin/sh, even when the /dev directory - on the rootfs is completely empty. + Automatically mount devtmpfs at /dev on the root filesystem, which + lets the system to come up in rescue mode with [rd]init=/bin/sh. + Override with devtmpfs.mount=0 on the commandline. Initramfs can + create a /dev dir as needed, other rootfs needs the mount point.
config STANDALONE bool "Select only drivers that don't need compile-time external firmware" diff --git a/init/main.c b/init/main.c index f866510..9ec09ff 100644 --- a/init/main.c +++ b/init/main.c @@ -1038,12 +1038,6 @@ static noinline void __init kernel_init_freeable(void)
do_basic_setup();
- /* Open the /dev/console on the rootfs, this should never fail */ - if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) - pr_err("Warning: unable to open an initial console.\n"); - - (void) sys_dup(0); - (void) sys_dup(0); /* * check if there is an early userspace init. If yes, let it do all * the work @@ -1055,8 +1049,17 @@ static noinline void __init kernel_init_freeable(void) if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) { ramdisk_execute_command = NULL; prepare_namespace(); + } else if (IS_ENABLED(CONFIG_DEVTMPFS_MOUNT)) { + sys_mkdir("/dev", 0755); + devtmpfs_mount("/dev"); }
+ /* Open the /dev/console on the rootfs, this should never fail */ + if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0) + pr_err("Warning: unable to open an initial console.\n"); + (void) sys_dup(0); + (void) sys_dup(0); + /* * Ok, we have completed the initial bootup, and * we're essentially up and running. Get rid of the