Re: [patch] delayed disk block allocation

Etienne Lorrain (etienne_lorrain@yahoo.fr)
Thu, 7 Mar 2002 13:06:09 +0100 (CET)


> 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.

Comment?
Etienne.

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