Re: [PATCH v8 05/10] qcow2_format.py: Dump bitmap directory information

[Vladimir Sementsov-Ogievskiy]

03.07.2020 16:13, Andrey Shinkevich wrote:
> Read and dump entries from the bitmap directory of QCOW2 image.
> It extends the output in the test case #291.
>
> Header extension:
> magic                     0x23852875 (Bitmaps)
> ...
>
> Bitmap name               bitmap-1
> bitmap_table_offset       0xf0000
> bitmap_table_size         1
> flags                     0x2 (['auto'])
> type                      1
> granularity_bits          16
> name_size                 8
> extra_data_size           0
>
> Suggested-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>   tests/qemu-iotests/291.out         | 45 ++++++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/qcow2_format.py | 44 +++++++++++++++++++++++++++++++++++++
>   2 files changed, 89 insertions(+)
>
> diff --git a/tests/qemu-iotests/291.out b/tests/qemu-iotests/291.out
> index 08bfaaa..53a8eeb 100644
> --- a/tests/qemu-iotests/291.out
> +++ b/tests/qemu-iotests/291.out
> @@ -33,6 +33,24 @@ reserved32                0
>   bitmap_directory_size     0x40
>   bitmap_directory_offset   0x510000
>   
> +Bitmap name               b1
> +bitmap_table_offset       0x4e0000
> +bitmap_table_size         1
> +flags                     0x0 ([])
> +type                      1
> +granularity_bits          19
> +name_size                 2
> +extra_data_size           0
> +
> +Bitmap name               b2
> +bitmap_table_offset       0x500000
> +bitmap_table_size         1
> +flags                     0x2 (['auto'])
> +type                      1
> +granularity_bits          16
> +name_size                 2
> +extra_data_size           0
> +
>   
>   === Bitmap preservation not possible to non-qcow2 ===
>   
> @@ -98,6 +116,33 @@ reserved32                0
>   bitmap_directory_size     0x60
>   bitmap_directory_offset   0x520000
>   
> +Bitmap name               b1
> +bitmap_table_offset       0x470000
> +bitmap_table_size         1
> +flags                     0x0 ([])
> +type                      1
> +granularity_bits          19
> +name_size                 2
> +extra_data_size           0
> +
> +Bitmap name               b2
> +bitmap_table_offset       0x490000
> +bitmap_table_size         1
> +flags                     0x2 (['auto'])
> +type                      1
> +granularity_bits          16
> +name_size                 2
> +extra_data_size           0
> +
> +Bitmap name               b0
> +bitmap_table_offset       0x510000
> +bitmap_table_size         1
> +flags                     0x0 ([])
> +type                      1
> +granularity_bits          16
> +name_size                 2
> +extra_data_size           0
> +
>   
>   === Check bitmap contents ===
>   
> diff --git a/tests/qemu-iotests/qcow2_format.py b/tests/qemu-iotests/qcow2_format.py
> index d8c058d..7c0dc9a 100644
> --- a/tests/qemu-iotests/qcow2_format.py
> +++ b/tests/qemu-iotests/qcow2_format.py
> @@ -132,6 +132,50 @@ class Qcow2BitmapExt(Qcow2Struct):
>   
>       def __init__(self, fd):
>           super().__init__(fd=fd)
> +        self.read_bitmap_directory(fd)
> +
> +    def read_bitmap_directory(self, fd):
> +        fd.seek(self.bitmap_directory_offset)
> +        self.bitmap_directory = \
> +            [Qcow2BitmapDirEntry(fd) for _ in range(self.nb_bitmaps)]

sounds good. I think, we should restore fd position after reading 
bitmap_directory, to point at the end of extension, to not break further 
extensions loading

> +
> +    def dump(self):
> +        super().dump()
> +        for entry in self.bitmap_directory:
> +            print()
> +            entry.dump()
> +
> +
> +class Qcow2BitmapDirEntry(Qcow2Struct):
> +
> +    fields = (
> +        ('u64', '{:#x}', 'bitmap_table_offset'),
> +        ('u32', '{}', 'bitmap_table_size'),
> +        ('u32', BitmapFlags, 'flags'),
> +        ('u8',  '{}', 'type'),
> +        ('u8',  '{}', 'granularity_bits'),
> +        ('u16', '{}', 'name_size'),
> +        ('u32', '{}', 'extra_data_size')
> +    )
> +
> +    def __init__(self, fd):
> +        super().__init__(fd=fd)
> +        # Seek relative to the current position in the file
> +        fd.seek(self.extra_data_size, 1)
> +        bitmap_name = fd.read(self.name_size)
> +        self.name = bitmap_name.decode('ascii')
> +        # Move position to the end of the entry in the directory
> +        entry_raw_size = self.bitmap_dir_entry_raw_size()
> +        padding = ((entry_raw_size + 7) & ~7) - entry_raw_size
> +        fd.seek(padding, 1)
> +
> +    def bitmap_dir_entry_raw_size(self):
> +        return struct.calcsize(self.fmt) + self.name_size + \
> +            self.extra_data_size
> +
> +    def dump(self):
> +        print(f'{"Bitmap name":<25} {self.name}')
> +        super(Qcow2BitmapDirEntry, self).dump()
>   
>   
>   QCOW2_EXT_MAGIC_BITMAPS = 0x23852875


--
Best regards,
Vladimir