Re: [PATCH parted] dasd: Fix ped_disk_new_fresh() to not read old data from disk (rh533808)

[Jim Meyering]

Hans de Goede wrote:
> dasd_write(), was reading the volume label from the disk (trough
> fdasd_check_volume()) and later writing it back again, this is fine for
> existing dasd labels, but when creating a fresh label, this would
> also cause the old volume label to be re-used, and if the old label
> was corrupt, it would cause fdasd_check_volume() and thus dasd_write()
> to fail.
>
> * libparted/arch/linux.c (toplevel): include fdasd.h.
> (init_dasd): Do BIODASDINFO ioctl, and store the dasd devno in
> arch_specific.
> (init_dasd): Remove dead (never reached) code.
> * libparted/arch/linux.h (struct _LinuxSpecific): Add devno member.
> * libparted/labels/dasd.c (DasdDiskSpecific): add vlabel member.
> (dasd_alloc): Init DasdDiskSpecific.vlabel for fresh disks
> (dasd_read): Store read vlabel in DasdDiskSpecific.vlabel.
> (dasd_write): Write DasdDiskSpecific.vlabel instead of on disk vlabel.

Thanks!
I'll do a thorough review tomorrow,
but in the mean time, would you please write a sentence about
this in NEWS?

Also, I want to be able to exercise this fix.
Assuming I have an s390 VM, I suppose I could
create a dasd partition table from a dd-created file
full of zeros, corrupt part of it, and then what?
Create another on top of that?  Is it the mklabel that fails?
Can you give enough detail so I can write a reproducer?