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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsitem
import (
"git.lukeshu.com/btrfs-progs-ng/lib/binstruct"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsprim"
"git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol"
)
// A BlockGroup tracks allocation of the logical address space.
//
// Compare with:
// - DevExtents, which track allocation of the physical address space.
// - Chunks, which map logical addresses to physical addresses.
//
// The relationship between the three is
//
// DevExtent---[many:one]---Chunk---[one:one]---BlockGroup
//
// Key:
//
// key.objectid = logical_addr
// key.offset = size of chunk
type BlockGroup struct { // trivial BLOCK_GROUP_ITEM=192
Used int64 `bin:"off=0, siz=8"`
ChunkObjectID btrfsprim.ObjID `bin:"off=8, siz=8"` // always FIRST_CHUNK_TREE_OBJECTID
Flags btrfsvol.BlockGroupFlags `bin:"off=16, siz=8"`
binstruct.End `bin:"off=24"`
}
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