Re: [PATCH] Wait and retry mounting root device (revised)

[Helge Hafting <helge.hafting@hist.no>]

Andrew Morton wrote:

>Helge Hafting <helge.hafting@hist.no> wrote:
>  
>
>>The USB block driver should know that 10s (or whatever) hasn't yet 
>> passed, and simply
>> block any attempt to access block devices (or scan for them) knowing 
>> that it will
>> not work yet, but any device will be there after the pause. A root mount 
>> on USB will
>> then succeed at the _first_ try everytime, so no need for retries.
>>    
>>
>
>Maybe a simple delay somewhere in the boot sequence would suffice?  Boot
>with `mount_delay=10'.
>
>  
>
Certainly the simplest solution, and it also solves a related
but rare problem: People booting linux from ROM long before
the disks have time to spin up.

There seems to be a disadvantage in that one must specify
this pause manually, but the admin have to select the root fs
somewhere anyway (lilo.conf) and may specify the delay at
the same time.

>But it sure would be nice to simply get this stuff right somehow.  If the
>USB block driver knows that discovery is still in progress it should wait
>until it has completed.  (I suggested that before, but wasn't 100% convinced
>by the answer).
>  
>
Sure, if the USB core can know, then it should use the knowledge.
Or utilize a simple timeout if all it knows is that "common
storage devices appear on the bus up to 10s after powerup/reset".

Helge Hafting