Hi
I staged the patch, thanks.
Mikulas
On Tue, 17 Mar 2026, Guillaume Gonnet wrote:
> The early_lookup_bdev() function returns successfully when the disk
> device is present but not necessarily its partitions. In this situation,
> dm_early_create() fails as the partition block device does not exist
> yet.
>
> In my case, this phenomenon occurs quite often because the device is
> an SD card with slow reading times, on which kernel takes time to
> enumerate available partitions.
>
> Fortunately, the underlying device is back to "probing" state while
> enumerating partitions. Waiting for all probing to end is enough to fix
> this issue.
>
> That's also the reason why this problem never occurs with rootwait=
> parameter: the while loop inside wait_for_root() explicitly waits for
> probing to be done and then the function calls async_synchronize_full().
> These lines were omitted in 035641b, even though the commit says it's
> based on the rootwait logic...
>
> Anyway, calling wait_for_device_probe() after our while loop does the
> job (it both waits for probing and calls async_synchronize_full).
>
> Fixes: 035641b01e72 ("dm init: add dm-mod.waitfor to wait for asynchronously
> probed block devices")
> Signed-off-by: Guillaume Gonnet <[email protected]>
> ---
>
> Hello,
>
> This patch is my attempt to fix the dm-mod.waitfor= issue. I had this
> fix for quite a while now, but I've never made the effort to contribute
> until recently.
>
> Some have tried to fix it this issue in the past but without finding
> its real root cause (ie. not waiting for device probe to end).
>
> Here are the links to those patches, for reference:
> https://lore.kernel.org/all/[email protected]/
> https://lore.kernel.org/all/[email protected]/
> https://lore.kernel.org/dm-devel/[email protected]/
>
> drivers/md/dm-init.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-init.c b/drivers/md/dm-init.c
> index 7403823384c5..c1bacba92c65 100644
> --- a/drivers/md/dm-init.c
> +++ b/drivers/md/dm-init.c
> @@ -303,8 +303,10 @@ static int __init dm_init_init(void)
> }
> }
>
> - if (waitfor[0])
> + if (waitfor[0]) {
> + wait_for_device_probe();
> DMINFO("all devices available");
> + }
>
> list_for_each_entry(dev, &devices, list) {
> if (dm_early_create(&dev->dmi, dev->table,
> --
> 2.43.0
>
