Re: [PATCH] Introduce a recovery= command line option.

[Janne Karhunen <janne.karhunen@gmail.com>]

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Hi,

Any comments on this? It would help my life considerably as I have to deal
with multiple bootloaders and royally hate initrds.


--
Janne

On Thu, Dec 3, 2015 at 8:35 AM, Janne Karhunen <Janne.Karhunen@gmail.com>
wrote:

> Recovery option can be used to define a secondary rootfs
> in case mounting of the primary root fails. While it has
> been possible to solve the issue via bootloader and/or
> initrd means, this solution is suitable for systems that
> want to stay bootloader agnostic and operate without an
> initrd.
>
> Signed-off-by: Janne Karhunen <Janne.Karhunen@gmail.com>
> ---
>  Documentation/kernel-parameters.txt |  3 ++
>  init/do_mounts.c                    | 64
> +++++++++++++++++++++++++++++--------
>  2 files changed, 54 insertions(+), 13 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 742f69d..0d65a63 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3390,6 +3390,9 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted.
>                 nocompress      Don't compress/decompress hibernation
> images.
>                 no              Disable hibernation and resume.
>
> +       recovery=       [KNL] Recovery root filesystem. This partition is
> attempted as
> +                       root in case default root filesystem does not
> mount.
> +
>         retain_initrd   [RAM] Keep initrd memory after extraction
>
>         rfkill.default_state=
> diff --git a/init/do_mounts.c b/init/do_mounts.c
> index dea5de9..994b2e5 100644
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -39,8 +39,11 @@ int __initdata rd_doload;    /* 1 = load RAM disk, 0 =
> don't load */
>
>  int root_mountflags = MS_RDONLY | MS_SILENT;
>  static char * __initdata root_device_name;
> +static char * __initdata recovery_device_name;
>  static char __initdata saved_root_name[64];
> +static char __initdata saved_recovery_name[64];
>  static int root_wait;
> +static int recovery_attempt;
>
>  dev_t ROOT_DEV;
>
> @@ -298,6 +301,15 @@ static int __init root_dev_setup(char *line)
>
>  __setup("root=", root_dev_setup);
>
> +static int __init recovery_setup(char *line)
> +{
> +       strlcpy(saved_recovery_name, line, sizeof(saved_recovery_name));
> +       recovery_attempt = 1;
> +       return 1;
> +}
> +
> +__setup("recovery=", recovery_setup);
> +
>  static int __init rootwait_setup(char *str)
>  {
>         if (*str)
> @@ -384,6 +396,7 @@ void __init mount_block_root(char *name, int flags)
>                                         __GFP_NOTRACK_FALSE_POSITIVE);
>         char *fs_names = page_address(page);
>         char *p;
> +       int err;
>  #ifdef CONFIG_BLOCK
>         char b[BDEVNAME_SIZE];
>  #else
> @@ -393,7 +406,7 @@ void __init mount_block_root(char *name, int flags)
>         get_fs_names(fs_names);
>  retry:
>         for (p = fs_names; *p; p += strlen(p)+1) {
> -               int err = do_mount_root(name, p, flags, root_mount_data);
> +               err = do_mount_root(name, p, flags, root_mount_data);
>                 switch (err) {
>                         case 0:
>                                 goto out;
> @@ -401,7 +414,33 @@ retry:
>                         case -EINVAL:
>                                 continue;
>                 }
> -               /*
> +               if (!(flags & MS_RDONLY)) {
> +                       pr_warn("Retrying rootfs mount as read-only.\n");
> +                       flags |= MS_RDONLY;
> +                       goto retry;
> +               }
> +               if (recovery_device_name && recovery_attempt) {
> +                       recovery_attempt = 0;
> +
> +                       ROOT_DEV = name_to_dev_t(recovery_device_name);
> +                       if (strncmp(recovery_device_name, "/dev/", 5) == 0)
> +                               recovery_device_name += 5;
> +
> +                       pr_warn("Unable to mount rootfs at %s, error
> %d.\n",
> +                               root_device_name, err);
> +                       pr_warn("Attempting %s for recovery as
> requested.\n",
> +                               recovery_device_name);
> +
> +                       err = create_dev("/dev/root", ROOT_DEV);
> +                       if (err < 0)
> +                               pr_emerg("Failed to re-create /dev/root:
> %d\n",
> +                                       err);
> +
> +                       root_device_name = recovery_device_name;
> +                       goto retry;
> +               }
> +
> +               /*
>                  * Allow the user to distinguish between failed sys_open
>                  * and bad superblock on root device.
>                  * and give them a list of the available devices
> @@ -409,28 +448,24 @@ retry:
>  #ifdef CONFIG_BLOCK
>                 __bdevname(ROOT_DEV, b);
>  #endif
> -               printk("VFS: Cannot open root device \"%s\" or %s: error
> %d\n",
> +               pr_emerg("VFS: Cannot open root device \"%s\" or %s: error
> %d\n",
>                                 root_device_name, b, err);
> -               printk("Please append a correct \"root=\" boot option;
> here are the available partitions:\n");
> +               pr_emerg("Please append a correct \"root=\" boot option;
> here are the available partitions:\n");
>
>                 printk_all_partitions();
>  #ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
> -               printk("DEBUG_BLOCK_EXT_DEVT is enabled, you need to
> specify "
> +               pr_emerg("DEBUG_BLOCK_EXT_DEVT is enabled, you need to
> specify "
>                        "explicit textual name for \"root=\" boot
> option.\n");
>  #endif
>                 panic("VFS: Unable to mount root fs on %s", b);
>         }
> -       if (!(flags & MS_RDONLY)) {
> -               flags |= MS_RDONLY;
> -               goto retry;
> -       }
>
> -       printk("List of all partitions:\n");
> +       pr_emerg("List of all partitions:\n");
>         printk_all_partitions();
> -       printk("No filesystem could mount root, tried: ");
> +       pr_emerg("No filesystem could mount root, tried: ");
>         for (p = fs_names; *p; p += strlen(p)+1)
> -               printk(" %s", p);
> -       printk("\n");
> +               pr_emerg(" %s", p);
> +       pr_emerg("\n");
>  #ifdef CONFIG_BLOCK
>         __bdevname(ROOT_DEV, b);
>  #endif
> @@ -567,6 +602,9 @@ void __init prepare_namespace(void)
>
>         md_run_setup();
>
> +       if (saved_recovery_name[0])
> +               recovery_device_name = saved_recovery_name;
> +
>         if (saved_root_name[0]) {
>                 root_device_name = saved_root_name;
>                 if (!strncmp(root_device_name, "mtd", 3) ||
> --
> 1.9.1
>
>

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