Re: [PATCH] speedy boot from usb devices

[Paulo Marques <pmarques@grupopie.com>]

David N. Welton wrote:
> [ Please CC replies to me - thanks! ]
> 
> Hi,
> 
> I gather that there isn't much interest in this idea on behalf of the
> 'mainstream', because initrd is a far more flexible solution, but I
> happen to like the idea of booting quickly from a USB device, without
> wasting a bunch of time and space for an initrd, and we're using this
> in a product as well, so without further ado, I'll point you at
> 
> http://dedasys.com/freesoftware/patches/
> 
> where you can get blkdev_wakeup.patch
> 
>         Works like so: whenever a block device comes on line, it
>         signals this fact to a wait queue, so that the init process
>         can stop and wait for slow devices, in particular things such
>         as USB storage devices, which are much slower than IDE
>         devices.  The init process checks the list of available
>         devices and compares it with the desired root device, and if
>         there is a match, proceeds with the initialization process,
>         secure in the knowledge that the device in question has been
>         brought up.  This is useful if one wants to boot quickly from
>         a USB storage device without a trimmed-down kernel, and
>         without going through the whole initrd slog.
> 
> Comments, critiques, suggestions and ideas are all welcome.

I find this to be very useful. I always found the "sleep for a while 
until the device we want appears" approach very cumbersome.

However, after looking at your patch, it seems that having a 
get_blkdevs() function that alloc's an array of strings, and return it 
to a function that only compares the strings against the name it is 
looking for and drops the array altogether, is a little overkill.

Why not have a simple blkdev_exists(char *name) function in genhd.c, 
call it directly, and drop the match_root_name() function completely?

Maybe I'm missing something, but it seems much simpler...

-- 
Paulo Marques - www.grupopie.com
"In a world without walls and fences who needs windows and gates?"