Re: [parted-devel] [Parted-maintainers] Debian Bug #578097: No support for CMS-formatted disks

[Jim Meyering]

[Cc'ing the list, in case others are interested. ]

Stephen Powell wrote:
> On Wed, 27 Oct 2010 06:08:14 -0400 (EDT), Jim Meyering wrote:
>> Stephen Powell wrote:
...
> But the new patch does assume,
> just like the one above-mentioned one does, that the four context diffs
> mentioned in your previous e-mail are already applied.
...
>
> OK, here is the new patch:
>
>    http://www.wowway.com/~zlinuxman/parted/parted_fba_diag_patch.diff

Thank you.
I confirmed that it applies and doesn't cause any trouble on x86_64/linux.
I'll actually look at the code and make sure tests pass on an
s390x next week, assuming I can get access.

Speaking of tests, can you outline a couple
that will exercise some (more the merrier) of this new code?

> In order to make the DIAG driver work for FBA DASD with a block
> size greater than 512, I had to make a rather awkward patch to
> C function vtoc_read_volume_label in libparted/labels/vtoc.c.
> The "right" logic would be "If this is an FBA DASD device
> using the DIAG driver, and the effective block size used by the
> DIAG driver is greater than 512, then do it this way.  Else,
> do it the normal way."  (Note that when using the FBA driver,
> the effective block size is always 512, regardless of the CMS
> logical block size stored in the volume label.  The DIAG driver,
> on the other hand, honors the CMS logical block size.)
>
> The problem is that the information needed to make that decision
> has not been provided to the routine (via the parameter list).
> So what I ended up doing is assuming the normal way, then if
> I don't find a recognized volume label header (VOL1, LNX1,
> or CMS1, in EBCDIC), then I assumed that it must be the special
> case.  So in the special case I end up doing an unnecessary
> read.  It's a kludge, but it works.
>
> Now about the NEWS article.  How about something like this?

Great.  I'll use it verbatim, with this tweak to the first sentence:

  Improve support of DASD devices on the s390 architecture.

> o A number of improvements have been made to the support of DASD
>   devices on the s390 architecture.  parted now supports all
>   DASD types (CKD and FBA), DASD formats (CDL, LDL, CMS
>   non-reserved, and CMS reserved), and DASD drivers (ECKD, FBA,
>   and DIAG) in all combinations supported by the Linux kernel.
>   As before, only CDL format on CKD DASD using the ECKD driver
>   is supported for read-write operations (create, delete,
>   move, re-size, etc.).  However, the implicit partition
>   present on LDL- and CMS-formatted disks is now correctly
>   recognized for read-only operations.  In detail:
>
>   - parted now correctly handles LDL-format disks with a block
>     size other than 4096 (bug fix)
>
>   - parted now recognizes the CMS disk format, both reserved
>     and non-reserved (enhancement)
>
>   - parted now supports FBA DASD devices (enhancement)
>
>   - parted now supports the DIAG driver when running in a
>     virtual machine under z/VM (enhancement)