Re: [PATCH] fix /boot/loader for extended slices
Matthew Dillon wrote:
> :> So what we need is some serious testing, e.g. like creating multiple
> :> extended dos partitions two recursions deep and seeing if the partition
> :> data is properly passed between the loader and kernel.
> :
> :First, your patch works just fine for me.
> :
> :Now, some comments on how the DOS extended partitions work, which I can
> :only infer from how the various fdisk programs work.
> :
> :I have only three fdisk programs which allow for extended partitions:
> :the ones from linux and NetBSD, and also the commercial Windows app
> :from Acronis -- well, and the MS versions of fdisk too, of course.
> :
> :They all behave the same when dealing with extended partitions -- that
> :is, they create the *primary* extended partition entry automatically
> :if there isn't one already. If there is an extended partition already
> :then it sticks your new logical drive at the end of the existing chain
> :of extended partitions. You never get the chance to create a second
> :*primary* extended slice.
> :
> :In other words, there will always be only one slice of type 05 among
> :the four primary partitions because there is no way to create a second
> :one. I even tried editing an existing partition to make it a type 05
> :and got an error message. Verboten!
> :
> :Second comment: I restricted the reading of each chained XPT to the
> :first two entries in the table because (on my machines) the last two
> :entries are always zeros. The first entry is the pointer to the
> :partition you really want (e.g. type a5 for DFLY) and the second
> :entry in the table is the pointer to the next XPT (i.e. always type
> :05.) There didn't seem to be any point in reading the last two.
> :
> :Doesn't matter -- your patch, as I said works fine. Thanks!
>
> Ok. I'll add some additional comments and then commit my modified patch.
> It's unclear what the official specification allows but the patched
> scanning code does check for zero'd entries and should handle those
> cases, and it does match what the kernel does.
>
> -Matt
> Matthew Dillon
> <dillon@backplane.com>
http://howtos.linux.com/howtos/Large-Disk-HOWTO-13.shtml
-Hiten
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