diff options
Diffstat (limited to 'lib/btrfs/btrfsitem/item_devextent.go')
| -rw-r--r-- | lib/btrfs/btrfsitem/item_devextent.go | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/lib/btrfs/btrfsitem/item_devextent.go b/lib/btrfs/btrfsitem/item_devextent.go index cade165..6998277 100644 --- a/lib/btrfs/btrfsitem/item_devextent.go +++ b/lib/btrfs/btrfsitem/item_devextent.go @@ -10,8 +10,23 @@ import ( "git.lukeshu.com/btrfs-progs-ng/lib/btrfs/btrfsvol" ) -// key.objectid = device_id -// key.offset = physical_addr +// A DevExtent tracks allocation of the physical address space. +// +// Compare with: +// - BlockGroups, which track allocation of the logical address space. +// - Chunks, which map logical addresses to physical addresses. +// +// The relationship between the three is +// +// DevExtent---[many:one]---Chunk---[one:one]---BlockGroup +// +// The device ID identifies which Dev item describes the physical +// volume that the DevExtent is on. +// +// Key: +// +// key.objectid = device_id +// key.offset = physical_addr type DevExtent struct { // trivial DEV_EXTENT=204 ChunkTree btrfsprim.ObjID `bin:"off=0, siz=8"` // always CHUNK_TREE_OBJECTID ChunkObjectID btrfsprim.ObjID `bin:"off=8, siz=8"` // which chunk within .ChunkTree owns this extent, always FIRST_CHUNK_TREE_OBJECTID |