Interesting patches for 4k drives w/ GPT

[Stefan Bader]

Mario Limonciello wrote:
> Hi,
> 
> Recently Colin Watson raised a bug (
> https://bugs.launchpad.net/bugs/511075
> <https://bugs.launchpad.net/bugs/511075>) to pull in Parted 2.1 for
> Lucid, particularly to be able to enable drives that use 4k sectors
> rather than 512 byte sectors.  As this FFe has been approved, it would
> probably be a good idea to support it from the kernel side too.  There
> are two patches related to using GPT with these types of drives from
> 2.6.33 that may be interesting to being able to support these drives:
> 
> commit 87038c2d5bda2418fda8b1456a0ae81cc3ff5bd8
> Author: Karel Zak <kzak at redhat.com>
> Date:   Mon Nov 23 09:29:58 2009 +0100
> 
>     partitions: read whole sector with EFI GPT header
>     
>     The size of EFI GPT header is not static, but whole sector is
>     allocated for the header. The HeaderSize field must be greater
>     than 92 (= sizeof(struct gpt_header) and must be less than or
>     equal to the logical block size.
>     
>     It means we have to read whole sector with the header, because the
>     header crc32 checksum is calculated according to HeaderSize.
>     
>     For more details see UEFI standard (version 2.3, May 2009):
>       - 5.3.1 GUID Format overview, page 93
>       - Table 13. GUID Partition Table Header, page 96
>     
>     Signed-off-by: Karel Zak <kzak at redhat.com>
>     Signed-off-by: Jens Axboe <jens.axboe at oracle.com>
> 
> commit 7d13af3279985f554784a45cc961f706dbcdbdd1
> Author: Karel Zak <kzak at redhat.com>
> Date:   Mon Nov 23 09:29:13 2009 +0100
> 
>     partitions: use sector size for EFI GPT
>     
>     Currently, kernel uses strictly 512-byte sectors for EFI GPT parsing.
>     That's wrong.
>     
>     UEFI standard (version 2.3, May 2009, 5.3.1 GUID Format overview, page
>     95) defines that LBA is always based on the logical block size. It
>     means bdev_logical_block_size() (aka BLKSSZGET) for Linux.
>     
>     This patch removes static sector size from EFI GPT parser.
>     
>     The problem is reproducible with the latest GNU Parted:
>     
>      # modprobe scsi_debug dev_size_mb=50 sector_size=4096
>     
>       # ./parted /dev/sdb print
>       Model: Linux scsi_debug (scsi)
>       Disk /dev/sdb: 52.4MB
>       Sector size (logical/physical): 4096B/4096B
>       Partition Table: gpt
>     
>       Number  Start   End     Size    File system  Name     Flags
>        1      24.6kB  3002kB  2978kB               primary
>        2      3002kB  6001kB  2998kB               primary
>        3      6001kB  9003kB  3002kB               primary
>     
>       # blockdev --rereadpt /dev/sdb
>       # dmesg | tail -1
>        sdb: unknown partition table      <---- !!!
>     
>     with this patch:
>     
>       # blockdev --rereadpt /dev/sdb
>       # dmesg | tail -1
>        sdb: sdb1 sdb2 sdb3
> 
> 
> 
Both of those are part of 2.6.32.9 which Andy will pull in after Alpha3 freeze
is done.

Cheers,
Stefan