qcow 0.10.0 · OCaml Package

type t

A cluster map which describes cluster usage in the file. The cluster map tracks which clusters are free, and which are used, and where the references are.

type move_state =

| Copying
(*
a background copy is in progress. If this cluster is modified then the copy should be aborted.
*)
| Copied
(*
contents of this cluster have been copied once to another cluster. If this cluster is modified then the copy should be aborted.
*)
| Flushed
(*
contents of this cluster have been copied and flushed to disk: it is now safe to rewrite the pointer. If this cluster is modified then the copy should be aborted.
*)
| Referenced
(*
the reference has been rewritten; it is now safe to write to this cluster again. On the next flush, the copy is complete and the original block can be recycled.
*)

Describes the state of a block move

type reference = Qcow_types.Cluster.t * int

module Move : sig ... end

type move = {

move : Move.t;
state : move_state;

}

describes the state of an in-progress block move

val string_of_move : move -> string

type cluster_state =

| Junk
| Erased
| Available
| Copies
| Roots
(*
The state of a cluster
*)

val set_cluster_state : 
  t ->
  Qcow_types.Cluster.IntervalSet.t ->
  cluster_state ->
  cluster_state ->
  unit

Update the state of a cluster

module type MutableSet = sig ... end

val zero : t

A cluster map for a zero-length disk

val make : 
  free:Qcow_bitmap.t ->
  refs:reference Qcow_types.Cluster.Map.t ->
  cache:Qcow_cache.t ->
  first_movable_cluster:Qcow_types.Cluster.t ->
  runtime_asserts:bool ->
  id:string option ->
  cluster_size:int ->
  t

Given a set of free clusters, and the first cluster which can be moved (i.e. that isn't fixed header), construct an empty cluster map.

val total_used : t -> int64

Return the number of tracked used clusters

val total_free : t -> int64

Return the number of tracked free clusters

val resize : t -> Qcow_types.Cluster.t -> unit

resize t new_size_clusters is called when the file is to be resized.

val add : t -> reference -> Qcow_types.Cluster.t -> unit

add t ref cluster marks cluster as in-use and notes the reference from reference.

val remove : t -> Qcow_types.Cluster.t -> unit

remove t cluster marks cluster as free and invalidates any reference to it (e.g. in response to a discard)

module Junk : MutableSet

Clusters which contain arbitrary data

module Erased : MutableSet

Clusters which have been erased but haven't been flushed yet so can't be safely reallocated.

module Available : MutableSet

Clusters which are available for reallocation

module Copies : MutableSet

Clusters which contain copies, as part of a compact

module Roots : MutableSet

Clusters which have been allocated but not yet placed somewhere reachable from the GC

val wait : t -> unit Lwt.t

wait t wait for some amount of recycling work to become available, e.g.

junk could be created
available could be used
a move might require a reference update

val start_moves : t -> Move.t list

start_moves t calculates the block moves required to compact t and marks the clusters as moving

val moves : t -> move Qcow_types.Cluster.Map.t

moves t returns the state of the current active moves

val set_move_state : t -> Move.t -> move_state -> unit

Update the state of the given move operation

val is_moving : t -> Qcow_types.Cluster.t -> bool

is_moving t cluster returns true if cluster is still moving

val cancel_move : t -> Qcow_types.Cluster.t -> unit

cancel_move cluster cancels any in-progress move of cluster cluster. This should be called with the cluster write lock held whenever there has been a change in the contents of cluster

val complete_move : t -> Move.t -> unit

complete_move t move marks the move as complete.

val find : t -> Qcow_types.Cluster.t -> reference

find t cluster returns the reference to cluster, or raises Not_found

val get_last_block : t -> Qcow_types.Cluster.t

get_last_block t is the last allocated block in t. Note if there are no data blocks this will point to the last header block even though it is immovable.

val is_immovable : t -> Qcow_types.Cluster.t -> bool

is_immovable t cluster is true if cluster is fixed and cannot be moved i.e. it is before the first_movable_cluster i.e. it is part of the fixed (L1) header structure.

val update_references : 
  t ->
  Qcow_types.Cluster.t Qcow_types.Cluster.Map.t ->
  unit

update_references t subst updates the reference table following the given set of substitutions. Any reference to a source block must be updated to the destination block otherwise it will be left pointing to junk. Normally this is guaranteed by the Metadata.Physical.set function, but when compacting we split the operation into phases and copy the block first at the byte level, leaving the map out-of-sync

val to_summary_string : t -> string

to_summary_string t returns a terse printable summary of t

module Debug : sig ... end

package qcow