Class: Lvm2Thin::SuperBlock

Inherits:
Object
  • Object
show all
Defined in:
lib/VolumeManager/LVM/thin/superblock.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#metadata_volume ⇒ Object

Returns the value of attribute metadata_volume.



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 3

def metadata_volume
  @metadata_volume
end

#struct ⇒ Object

Returns the value of attribute struct.



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 5

def struct
  @struct
end

Class Method Details

.get(metadata_volume) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 7

def self.get(metadata_volume)
  @superblock ||= begin
    superblock = SuperBlock.new
    superblock.metadata_volume = metadata_volume
    superblock.seek 0
    superblock.struct = superblock.read_struct SUPERBLOCK
    raise "unknown lvm2 thin metadata magic number" if superblock.struct.magic != THIN_MAGIC
    superblock
  end
end

Instance Method Details

#data_block_address(blk_addr) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 36

def data_block_address(blk_addr)
  blk_addr * data_block_size
end

#data_block_size ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 32

def data_block_size
  @data_block_size ||= struct['data_block_size'] * 512
end

#data_mapping ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 60

def data_mapping
  @data_mapping ||= MappingTree.new self, data_mapping_address
end

#data_mapping_address ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 56

def data_mapping_address
  @data_mapping_address ||= md_block_address(struct['data_mapping_root'])
end

#data_space_map ⇒ Object

lvm thin structures:



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 42

def data_space_map
  @data_space_map ||= begin
    seek SUPERBLOCK.offset('data_space_map_root')
    DataSpaceMap.new self, read_struct(SPACE_MAP)
  end
end

#device_block(device_address) ⇒ Object

address resolution / mapping:



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 74

def device_block(device_address)
  (device_address / data_block_size).to_i
end

#device_block_offset(device_address) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 78

def device_block_offset(device_address)
  device_address % data_block_size
end

#device_details ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 68

def device_details
  @device_details ||= BTree.new self, device_details_address, DEVICE_DETAILS
end

#device_details_address ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 64

def device_details_address
  @device_details_address ||= md_block_address(struct['device_details_root'])
end

#device_to_data(device_id, pos, len) ⇒ Object

Return array of tuples device block ids, data block ids, addresses, and lengths to read from them to read the specified device offset & length.

Note: data blocks may not amount to total requested length (if requesting data from unallocated space).

See Also:



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 89

def device_to_data(device_id, pos, len)
  dev_blk  = device_block(pos)
  dev_off  = device_block_offset(pos)
  data_map = data_mapping.map_for(device_id)

  total_len = 0
  data_blks = []

  num_data_blks = (len / data_block_size).to_i + 1
  0.upto(num_data_blks - 1) do |i|
    current_blk = dev_blk + i
    blk_len = 0

    if data_map.block?(current_blk)
      data_blk = data_map.data_block(current_blk)
      blk_start = data_blk * data_block_size

      if i.zero?
        blk_start += dev_off
        blk_len    = data_block_size - dev_off - 1

      elsif i == num_data_blks - 1
        blk_len = len - total_len

      else
        blk_len = data_block_size
      end

      data_blks << [current_blk, data_blk, blk_start, blk_len]

    # Missing block may be caused by trying to read beyond end of
    # LVM device (too large pos or len):
    else
      remaining  = (len - total_len)
      blk_len    = remaining > data_block_size ? data_block_size : remaining
      data_blks << [current_blk, nil, nil, blk_len]
    end

    total_len += blk_len
  end

  data_blks
end

#entries_per_block ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 28

def entries_per_block
  @entries_per_block ||= (md_block_size - BITMAP_HEADER.size) * 4
end

#md_block_address(blk_addr) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 24

def md_block_address(blk_addr)
  blk_addr * md_block_size
end

#md_block_size ⇒ Object

superblock properties:



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 20

def md_block_size
  @md_block_size ||= struct['metadata_block_size'] * 512 # = 4096
end

#metadata_space_map ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 49

def metadata_space_map
  @metadata_space_map ||= begin
    seek SUPERBLOCK.offset('metadata_space_map_root')
    MetadataSpaceMap.new self, read_struct(SPACE_MAP)
  end
end

#read(n) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 139

def read(n)
  @metadata_volume.disk.read n
end

#read_struct(struct) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 143

def read_struct(struct)
  OpenStruct.new(struct.decode(@metadata_volume.disk.read(struct.size)))
end

#read_structs(struct, num) ⇒ Object 



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 147

def read_structs(struct, num)
  Array.new(num) do
    read_struct struct
  end
end

#seek(pos) ⇒ Object

metadata volume disk helpers:



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# File 'lib/VolumeManager/LVM/thin/superblock.rb', line 135

def seek(pos)
  @metadata_volume.disk.seek pos
end