Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751427AbdIMXve (ORCPT ); Wed, 13 Sep 2017 19:51:34 -0400 Received: from mail-qt0-f193.google.com ([209.85.216.193]:37464 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751279AbdIMXvb (ORCPT ); Wed, 13 Sep 2017 19:51:31 -0400 X-Google-Smtp-Source: AOwi7QAMx+znzEfXXdZqMCa5wjDg6xsdrhzAkS1cIDLec9WuvLFR4sVPx6UZc+s3xZ5UGjtyw0IGhQ== To: Michael Ellerman , Stephen Rothwell Cc: Abdul Haleem , linuxppc-dev , gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, mingo@kernel.org, akpm@linux-foundation.org, keescook@chromium.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, mhocko@suse.com, viresh.kumar@linaro.org, tj@kernel.org, thomas.lendacky@amd.com, lauraa@codeaurora.org, lokeshvutla@ti.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-input@vger.kernel.org, Jiri Kosina , Benjamin Tissoires , sachinp , Andrew Morton References: <1495700957.9020.43.camel@abdul.in.ibm.com> <8760gp9jjl.fsf@concordia.ellerman.id.au> <20170526072437.46499fbd@canb.auug.org.au> <87a7e82d-0af5-7f9e-6bd6-7e28b238e866@landley.net> <87r2z86ykt.fsf@concordia.ellerman.id.au> From: Rob Landley Subject: [PATCH v3] Make initramfs honor CONFIG_DEVTMPFS_MOUNT Message-ID: <4aa9cb26-f868-0720-e5c8-3c4e08afad20@landley.net> Date: Wed, 13 Sep 2017 18:51:25 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <87r2z86ykt.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3853 Lines: 103 From: Rob Landley Make initramfs honor CONFIG_DEVTMPFS_MOUNT, and move /dev/console open after devtmpfs mount. Add workaround for Debian bug that was copied by Ubuntu. Signed-off-by: Rob Landley --- v2 discussion: http://lkml.iu.edu/hypermail/linux/kernel/1705.2/05611.html drivers/base/Kconfig | 14 ++++---------- fs/namespace.c | 14 ++++++++++++++ init/main.c | 15 +++++++++------ 3 files changed, 27 insertions(+), 16 deletions(-) diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index f046d21..97352d4 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/fs/namespace.c b/fs/namespace.c index f8893dc..06057d7 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2417,7 +2417,21 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) err = -EBUSY; if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path->mnt->mnt_root == path->dentry) + { + if (IS_ENABLED(CONFIG_DEVTMPFS_MOUNT) && + !strcmp(path->mnt->mnt_sb->s_type->name, "devtmpfs")) + { + /* Debian's kernel config enables DEVTMPFS_MOUNT, then + its initramfs setup script tries to mount devtmpfs + again, and if the second mount-over-itself fails + the script overmounts a tmpfs on /dev to hide the + existing contents, then boot fails with empty /dev. */ + printk(KERN_WARNING "Debian bug workaround for devtmpfs overmount."); + + err = 0; + } goto unlock; + } err = -EINVAL; if (d_is_symlink(newmnt->mnt.mnt_root)) diff --git a/init/main.c b/init/main.c index 0ee9c686..0d8e5ec 100644 --- a/init/main.c +++ b/init/main.c @@ -1065,12 +1065,6 @@ 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 @@ -1082,8 +1076,17 @@ 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