Messages in this thread | | | Subject | Re: [PATCH v3] Make initramfs honor CONFIG_DEVTMPFS_MOUNT | From | Christophe LEROY <> | Date | Thu, 14 Sep 2017 11:17:16 +0200 |
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Le 14/09/2017 à 01:51, Rob Landley a écrit : > From: Rob Landley <rob@landley.net> > > Make initramfs honor CONFIG_DEVTMPFS_MOUNT, and move > /dev/console open after devtmpfs mount. > > Add workaround for Debian bug that was copied by Ubuntu.
Is that a bug only for Debian ? Why ? Why should a Debian bug be fixed by a workaround in the mainline kernel ?
> > Signed-off-by: Rob Landley <rob@landley.net> > --- > > 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.
Why modifying the initial text ? Why talking about rescue mode only, whereas this feature mainly concerns the standard mode.
> > 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. */
Does it matter for the kernel code what Debian's kernel config does ?
> + printk(KERN_WARNING "Debian bug workaround for devtmpfs overmount.");
Is this log message worth it when this modification goes in mainline kernel ?
If so, pr_err() should be used instead.
> + > + 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);
Why not, but couldn't we also expect the initramfs to already contains that mountpoint ?
> + 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 >
Christophe
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