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

[Helge Hafting]

Andrew Morton wrote:

> Helge Hafting <helge.hafting@xxxxxxx> 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
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