On Wed, Jul 26, 2023 at 11:08:35PM -0700, Randy Dunlap wrote:
> Hi--
>
> On 7/26/23 08:22, Loic Poulain wrote:
> > Add an optional timeout arg to 'rootwait' as the maximum time in
> > seconds to wait for the root device to show up before attempting
> > forced mount of the root filesystem.
> >
> > Use case:
> > In case of device mapper usage for the rootfs (e.g. root=/dev/dm-0),
> > if the mapper is not able to create the virtual block for any reason
> > (wrong arguments, bad dm-verity signature, etc), the `rootwait` param
> > causes the kernel to wait forever. It may however be desirable to only
> > wait for a given time and then panic (force mount) to cause device reset.
> > This gives the bootloader a chance to detect the problem and to take some
> > measures, such as marking the booted partition as bad (for A/B case) or
> > entering a recovery mode.
> >
> > In success case, mounting happens as soon as the root device is ready,
> > unlike the existing 'rootdelay' parameter which performs an unconditional
> > pause.
> >
> > Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxx>
> > ---
> > v2: rebase + reword: add use case example
> >
> > .../admin-guide/kernel-parameters.txt | 4 ++++
> > init/do_mounts.c | 19 +++++++++++++++++--
> > 2 files changed, 21 insertions(+), 2 deletions(-)
> >
>
> > diff --git a/init/do_mounts.c b/init/do_mounts.c
> > index 1aa015883519..118f2bbe7b38 100644
> > --- a/init/do_mounts.c
> > +++ b/init/do_mounts.c
> > @@ -18,6 +18,7 @@
> > #include <linux/slab.h>
> > #include <linux/ramfs.h>
> > #include <linux/shmem_fs.h>
> > +#include <linux/ktime.h>
> >
> > #include <linux/nfs_fs.h>
> > #include <linux/nfs_fs_sb.h>
> > @@ -71,12 +72,20 @@ static int __init rootwait_setup(char *str)
> > {
> > if (*str)
> > return 0;
> > - root_wait = 1;
> > + root_wait = -1;
> > return 1;
> > }
> >
> > __setup("rootwait", rootwait_setup);
> >
> > +static int __init rootwait_timeout_setup(char *str)
> > +{
> > + root_wait = simple_strtoul(str, NULL, 0);
>
> Better to use kstrtoul(). simple_strtoul() says:
>
> * This function has caveats. Please use kstrtoul instead.
>
> and kstrtoul() says:
>
> * Returns 0 on success, -ERANGE on overflow and -EINVAL on parsing error.
> * Preferred over simple_strtoul(). Return code must be checked.
Yes, this should check and at least log an error that rootwait is
ignored and fall back to either indefinite waiting or no waiting.
