[OE-core] [PATCH 1/1] wic: fix extended/logical partition layout

[Maciej Borzecki]

ping

On 01/09 14:24, Maciej Borzecki wrote:
> The patch fixes an issue in laying out extended and logical partitions
> by wic. The original code produced disk images in which the size 3rd
> partition as described in MBR was incorrect. Depending on the type of
> file system used for that partition and size of the partition, it would
> be impossible to mount the partition correctly. For instance, kickstart
> file in which the 3rd partition had size of 1GB and used ext4 fs, would
> result in an image with an umountable partition. The root cause is
> reservation of sectors for EBR through stealing of last sector from the
> last primary partition.
>
> Signed-off-by: Maciej Borzecki <maciej.borzecki at open-rnd.pl>
> Signed-off-by: Maciek Borzecki <maciek.borzecki at gmail.com>
> ---
>  scripts/lib/wic/utils/partitionedfs.py | 40 ++++++++++++++++------------------
>  1 file changed, 19 insertions(+), 21 deletions(-)
>
> diff --git a/scripts/lib/wic/utils/partitionedfs.py b/scripts/lib/wic/utils/partitionedfs.py
> index fb95cc7..9df93dc 100644
> --- a/scripts/lib/wic/utils/partitionedfs.py
> +++ b/scripts/lib/wic/utils/partitionedfs.py
> @@ -156,6 +156,13 @@ class Image:
>                  # Skip one sector required for the partitioning scheme overhead
>                  d['offset'] += overhead
>
> +            elif d['numpart'] > 3:
> +                # Reserve a sector for EBR for every logical partition
> +                # before alignment is performed.
> +                if ptable_format == "msdos":
> +                    d['offset'] += 1
> +
> +
>              if p['align']:
>                  # If not first partition and we do have alignment set we need
>                  # to align the partition.
> @@ -185,14 +192,6 @@ class Image:
>              p['num'] = d['numpart']
>
>              if d['ptable_format'] == "msdos":
> -                if d['numpart'] > 2:
> -                    # Every logical partition requires an additional sector for
> -                    # the EBR, so steal the last sector from the end of each
> -                    # partition starting from the 3rd one for the EBR. This
> -                    # will make sure the logical partitions are aligned
> -                    # correctly.
> -                    p['size'] -= 1
> -
>                  if d['numpart'] > 3:
>                      p['type'] = 'logical'
>                      p['num'] = d['numpart'] + 1
> @@ -259,13 +258,20 @@ class Image:
>          for p in self.partitions:
>              d = self.disks[p['disk_name']]
>              if d['ptable_format'] == "msdos" and p['num'] == 5:
> -                # The last sector of the 3rd partition was reserved for the EBR
> -                # of the first _logical_ partition. This is why the extended
> -                # partition should start one sector before the first logical
> -                # partition.
> +                # Create an extended partition (note: extended
> +                # partition is described in MBR and contains all
> +                # logical partitions). The logical partitions save a
> +                # sector for an EBR just before the start of a
> +                # partition. The extended partition must start one
> +                # sector before the start of the first logical
> +                # partition. This way the first EBR is inside of the
> +                # extended partition. Since the extended partitions
> +                # starts a sector before the first logical partition,
> +                # add a sector at the back, so that there is enough
> +                # room for all logical partitions.
>                  self.__create_partition(d['disk'].device, "extended",
>                                          None, p['start'] - 1,
> -                                        d['offset'] - p['start'])
> +                                        d['offset'] - p['start'] + 1)
>
>              if p['fstype'] == "swap":
>                  parted_fs_type = "linux-swap"
> @@ -338,14 +344,6 @@ class Image:
>
>          for p in self.partitions:
>              d = self.disks[p['disk_name']]
> -            if d['ptable_format'] == "msdos" and p['num'] == 5:
> -                # The last sector of the 3rd partition was reserved for the EBR
> -                # of the first _logical_ partition. This is why the extended
> -                # partition should start one sector before the first logical
> -                # partition.
> -                self.__write_partition(p['num'], p['source_file'],
> -                                       p['start'] - 1,
> -                                       d['offset'] - p['start'])
>
>              self.__write_partition(p['num'], p['source_file'],
>                                     p['start'], p['size'])
> --
> 1.9.3
>
> --
> _______________________________________________
> Openembedded-core mailing list
> Openembedded-core at lists.openembedded.org
> http://lists.openembedded.org/mailman/listinfo/openembedded-core

--
Maciej Borzęcki
Senior Software Developer at Open-RnD Sp. z o.o., Poland
www.open-rnd.pl
mobile: +48 889 117 365, fax: +48 42 657 9079


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