block: document job API

I am not sure that these are really proper GtkDoc, but they follow
the existing documentation in block_int.h.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block_int.h

@@ -63,8 +63,13 @@ typedef struct BlockIOBaseValue {
     uint64_t ios[2];
 } BlockIOBaseValue;
 
-typedef void BlockJobCancelFunc(void *opaque);
 typedef struct BlockJob BlockJob;
+
+/**
+ * BlockJobType:
+ *
+ * A class type for block job objects.
+ */
 typedef struct BlockJobType {
     /** Derived BlockJob struct size */
     size_t instance_size;
@@ -77,20 +82,48 @@ typedef struct BlockJobType {
 } BlockJobType;
 
 /**
- * Long-running operation on a BlockDriverState
+ * BlockJob:
+ *
+ * Long-running operation on a BlockDriverState.
  */
 struct BlockJob {
+    /** The job type, including the job vtable.  */
     const BlockJobType *job_type;
+
+    /** The block device on which the job is operating.  */
     BlockDriverState *bs;
+
+    /**
+     * Set to true if the job should cancel itself.  The flag must
+     * always be tested just before toggling the busy flag from false
+     * to true.  After a job has detected that the cancelled flag is
+     * true, it should not anymore issue any I/O operation to the
+     * block device.
+     */
     bool cancelled;
+
+    /**
+     * Set to false by the job while it is in a quiescent state, where
+     * no I/O is pending and cancellation can be processed without
+     * issuing new I/O.  The busy flag must be set to false when the
+     * job goes to sleep on any condition that is not detected by
+     * #qemu_aio_wait, such as a timer.
+     */
     bool busy;
 
-    /* These fields are published by the query-block-jobs QMP API */
+    /** Offset that is published by the query-block-jobs QMP API */
     int64_t offset;
+
+    /** Length that is published by the query-block-jobs QMP API */
     int64_t len;
+
+    /** Speed that was set with @block_job_set_speed.  */
     int64_t speed;
 
+    /** The completion function that will be called when the job completes.  */
     BlockDriverCompletionFunc *cb;
+
+    /** The opaque value that is passed to the completion function.  */
     void *opaque;
 };
 
@@ -306,14 +339,90 @@ void bdrv_set_io_limits(BlockDriverState *bs,
 int is_windows_drive(const char *filename);
 #endif
 
+/**
+ * block_job_create:
+ * @job_type: The class object for the newly-created job.
+ * @bs: The block
+ * @cb: Completion function for the job.
+ * @opaque: Opaque pointer value passed to @cb.
+ *
+ * Create a new long-running block device job and return it.  The job
+ * will call @cb asynchronously when the job completes.  Note that
+ * @bs may have been closed at the time the @cb it is called.  If
+ * this is the case, the job may be reported as either cancelled or
+ * completed.
+ *
+ * This function is not part of the public job interface; it should be
+ * called from a wrapper that is specific to the job type.
+ */
 void *block_job_create(const BlockJobType *job_type, BlockDriverState *bs,
                        BlockDriverCompletionFunc *cb, void *opaque);
+
+/**
+ * block_job_complete:
+ * @job: The job being completed.
+ * @ret: The status code.
+ *
+ * Call the completion function that was registered at creation time, and
+ * free @job.
+ */
 void block_job_complete(BlockJob *job, int ret);
+
+/**
+ * block_job_set_speed:
+ * @job: The job to set the speed for.
+ * @speed: The new value
+ *
+ * Set a rate-limiting parameter for the job; the actual meaning may
+ * vary depending on the job type.
+ */
 int block_job_set_speed(BlockJob *job, int64_t value);
+
+/**
+ * block_job_cancel:
+ * @job: The job to be canceled.
+ *
+ * Asynchronously cancel the specified job.
+ */
 void block_job_cancel(BlockJob *job);
+
+/**
+ * block_job_is_cancelled:
+ * @job: The job being queried.
+ *
+ * Returns whether the job is scheduled for cancellation.
+ */
 bool block_job_is_cancelled(BlockJob *job);
+
+/**
+ * block_job_cancel:
+ * @job: The job to be canceled.
+ *
+ * Asynchronously cancel the job and wait for it to reach a quiescent
+ * state.  Note that the completion callback will still be called
+ * asynchronously, hence it is *not* valid to call #bdrv_delete
+ * immediately after #block_job_cancel_sync.  Users of block jobs
+ * will usually protect the BlockDriverState objects with a reference
+ * count, should this be a concern.
+ */
 void block_job_cancel_sync(BlockJob *job);
 
+/**
+ * stream_start:
+ * @bs: Block device to operate on.
+ * @base: Block device that will become the new base, or %NULL to
+ * flatten the whole backing file chain onto @bs.
+ * @base_id: The file name that will be written to @bs as the new
+ * backing file if the job completes.  Ignored if @base is %NULL.
+ * @cb: Completion function for the job.
+ * @opaque: Opaque pointer value passed to @cb.
+ *
+ * Start a streaming operation on @bs.  Clusters that are unallocated
+ * in @bs, but allocated in any image between @base and @bs (both
+ * exclusive) will be written to @bs.  At the end of a successful
+ * streaming job, the backing file of @bs will be changed to
+ * @base_id in the written image and to @base in the live BlockDriverState.
+ */
 int stream_start(BlockDriverState *bs, BlockDriverState *base,
                  const char *base_id, BlockDriverCompletionFunc *cb,
                  void *opaque);