Re: [patch] delayed disk block allocation

[Mike Fedyk <mfedyk@matchmail.com>]

On Thu, Mar 07, 2002 at 08:47:24AM -0600, Steve Lord wrote:
> On Thu, 2002-03-07 at 06:06, Etienne Lorrain wrote:
> > > With "allocate on flush", (aka delayed allocation), file data is
> > > assigned a disk mapping when the data is being written out, rather than
> > > at write(2) time.  This has the following advantages:
> > 
> >   I do agree that this is a better solution than current one,
> >  but (even if I did not had time to test the patch), I have
> >  a question: How about bootloaders?
> > 
> >  IHMO all current bootloaders need to write to disk a "chain" of sector
> >  to load for their own initialisation, i.e. loading the remainning
> >  part of code stored on a file in one filesystem from the 512 bytes
> >  bootcode. This "chain" of sector can only be known once the file
> >  has been allocated to disk - and it has to be written on the same file,
> >  at its allocated space.
> > 
> >   So can you upgrade LILO or GRUB with your patch installed?
> >   It is not a so big problem (the solution being to install the
> >  bootloader on an unmounted filesystem with tools like e2fsprogs),
> >  but it seems incompatible with the current executables.
> 
> The interface used by lilo to read the kernel location needs to flush
> data out to disk before returning results. It's not too hard to do.
> 

Also, GRUB shouldn't have this problem since it reads the filesystems
directly on boot.