include/block/blockjob.h

/*
 * Declarations for long-running block device operations
 *
 * Copyright (c) 2011 IBM Corp.
 * Copyright (c) 2012 Red Hat, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef BLOCKJOB_H
#define BLOCKJOB_H

#include "block/block.h"

/**
 * BlockJobDriver:
 *
 * A class type for block job driver.
 */
typedef struct BlockJobDriver {
    /** Derived BlockJob struct size */
    size_t instance_size;

    /** String describing the operation, part of query-block-jobs QMP API */
    BlockJobType job_type;

    /** Optional callback for job types that support setting a speed limit */
    void (*set_speed)(BlockJob *job, int64_t speed, Error **errp);

    /** Optional callback for job types that need to forward I/O status reset */
    void (*iostatus_reset)(BlockJob *job);

    /**
     * Optional callback for job types whose completion must be triggered
     * manually.
     */
    void (*complete)(BlockJob *job, Error **errp);

    /**
     * If the callback is not NULL, it will be invoked when all the jobs
     * belonging to the same transaction complete; or upon this job's
     * completion if it is not in a transaction. Skipped if NULL.
     *
     * All jobs will complete with a call to either .commit() or .abort() but
     * never both.
     */
    void (*commit)(BlockJob *job);

    /**
     * If the callback is not NULL, it will be invoked when any job in the
     * same transaction fails; or upon this job's failure (due to error or
     * cancellation) if it is not in a transaction. Skipped if NULL.
     *
     * All jobs will complete with a call to either .commit() or .abort() but
     * never both.
     */
    void (*abort)(BlockJob *job);

    /**
     * If the callback is not NULL, it will be invoked when the job transitions
     * into the paused state.  Paused jobs must not perform any asynchronous
     * I/O or event loop activity.  This callback is used to quiesce jobs.
     */
    void coroutine_fn (*pause)(BlockJob *job);

    /**
     * If the callback is not NULL, it will be invoked when the job transitions
     * out of the paused state.  Any asynchronous I/O or event loop activity
     * should be restarted from this callback.
     */
    void coroutine_fn (*resume)(BlockJob *job);

    /*
     * If the callback is not NULL, it will be invoked before the job is
     * resumed in a new AioContext.  This is the place to move any resources
     * besides job->blk to the new AioContext.
     */
    void (*attached_aio_context)(BlockJob *job, AioContext *new_context);
} BlockJobDriver;

/**
 * BlockJob:
 *
 * Long-running operation on a BlockDriverState.
 */
struct BlockJob {
    /** The job type, including the job vtable.  */
    const BlockJobDriver *driver;

    /** The block device on which the job is operating.  */
    BlockBackend *blk;

    /**
     * The ID of the block job. Currently the BlockBackend name of the BDS
     * owning the job at the time when the job is started.
     *
     * TODO Decouple block job IDs from BlockBackend names
     */
    char *id;

    /**
     * The coroutine that executes the job.  If not NULL, it is
     * reentered when busy is false and the job is cancelled.
     */
    Coroutine *co;

    /**
     * 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 been cancelled, it should only yield
     * if #aio_poll will ("sooner or later") reenter the coroutine.
     */
    bool cancelled;

    /**
     * Counter for pause request. If non-zero, the block job is either paused,
     * or if busy == true will pause itself as soon as possible.
     */
    int pause_count;

    /**
     * Set to true if the job is paused by user.  Can be unpaused with the
     * block-job-resume QMP command.
     */
    bool user_paused;

    /**
     * Set to false by the job while the coroutine has yielded and may be
     * re-entered by block_job_enter().  There may still be I/O or event loop
     * activity pending.
     */
    bool busy;

    /**
     * Set to true by the job while it is in a quiescent state, where
     * no I/O or event loop activity is pending.
     */
    bool paused;

    /**
     * Set to true when the job is ready to be completed.
     */
    bool ready;

    /**
     * Set to true when the job has deferred work to the main loop.
     */
    bool deferred_to_main_loop;

    /** Element of the list of block jobs */
    QLIST_ENTRY(BlockJob) job_list;

    /** Status that is published by the query-block-jobs QMP API */
    BlockDeviceIoStatus iostatus;

    /** 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.  */
    BlockCompletionFunc *cb;

    /** Block other operations when block job is running */
    Error *blocker;

    /** The opaque value that is passed to the completion function.  */
    void *opaque;

    /** Reference count of the block job */
    int refcnt;

    /* True if this job has reported completion by calling block_job_completed.
     */
    bool completed;

    /* ret code passed to block_job_completed.
     */
    int ret;

    /** Non-NULL if this job is part of a transaction */
    BlockJobTxn *txn;
    QLIST_ENTRY(BlockJob) txn_list;
};

/**
 * block_job_next:
 * @job: A block job, or %NULL.
 *
 * Get the next element from the list of block jobs after @job, or the
 * first one if @job is %NULL.
 *
 * Returns the requested job, or %NULL if there are no more jobs left.
 */
BlockJob *block_job_next(BlockJob *job);

/**
 * block_job_create:
 * @job_type: The class object for the newly-created job.
 * @bs: The block
 * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
 * @cb: Completion function for the job.
 * @opaque: Opaque pointer value passed to @cb.
 * @errp: Error object.
 *
 * 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 BlockJobDriver *driver, BlockDriverState *bs,
                       int64_t speed, BlockCompletionFunc *cb,
                       void *opaque, Error **errp);

/**
 * block_job_sleep_ns:
 * @job: The job that calls the function.
 * @clock: The clock to sleep on.
 * @ns: How many nanoseconds to stop for.
 *
 * Put the job to sleep (assuming that it wasn't canceled) for @ns
 * nanoseconds.  Canceling the job will interrupt the wait immediately.
 */
void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns);

/**
 * block_job_yield:
 * @job: The job that calls the function.
 *
 * Yield the block job coroutine.
 */
void block_job_yield(BlockJob *job);

/**
 * block_job_ref:
 * @bs: The block device.
 *
 * Grab a reference to the block job. Should be paired with block_job_unref.
 */
void block_job_ref(BlockJob *job);

/**
 * block_job_unref:
 * @bs: The block device.
 *
 * Release reference to the block job and release resources if it is the last
 * reference.
 */
void block_job_unref(BlockJob *job);

/**
 * block_job_completed:
 * @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_completed(BlockJob *job, int ret);

/**
 * block_job_set_speed:
 * @job: The job to set the speed for.
 * @speed: The new value
 * @errp: Error object.
 *
 * Set a rate-limiting parameter for the job; the actual meaning may
 * vary depending on the job type.
 */
void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp);

/**
 * block_job_cancel:
 * @job: The job to be canceled.
 *
 * Asynchronously cancel the specified job.
 */
void block_job_cancel(BlockJob *job);

/**
 * block_job_complete:
 * @job: The job to be completed.
 * @errp: Error object.
 *
 * Asynchronously complete the specified job.
 */
void block_job_complete(BlockJob *job, Error **errp);

/**
 * 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_query:
 * @job: The job to get information about.
 *
 * Return information about a job.
 */
BlockJobInfo *block_job_query(BlockJob *job);

/**
 * block_job_pause_point:
 * @job: The job that is ready to pause.
 *
 * Pause now if block_job_pause() has been called.  Block jobs that perform
 * lots of I/O must call this between requests so that the job can be paused.
 */
void coroutine_fn block_job_pause_point(BlockJob *job);

/**
 * block_job_pause:
 * @job: The job to be paused.
 *
 * Asynchronously pause the specified job.
 */
void block_job_pause(BlockJob *job);

/**
 * block_job_resume:
 * @job: The job to be resumed.
 *
 * Resume the specified job.  Must be paired with a preceding block_job_pause.
 */
void block_job_resume(BlockJob *job);

/**
 * block_job_enter:
 * @job: The job to enter.
 *
 * Continue the specified job by entering the coroutine.
 */
void block_job_enter(BlockJob *job);

/**
 * block_job_event_cancelled:
 * @job: The job whose information is requested.
 *
 * Send a BLOCK_JOB_CANCELLED event for the specified job.
 */
void block_job_event_cancelled(BlockJob *job);

/**
 * block_job_ready:
 * @job: The job which is now ready to complete.
 * @msg: Error message. Only present on failure.
 *
 * Send a BLOCK_JOB_COMPLETED event for the specified job.
 */
void block_job_event_completed(BlockJob *job, const char *msg);

/**
 * block_job_ready:
 * @job: The job which is now ready to complete.
 *
 * Send a BLOCK_JOB_READY event for the specified job.
 */
void block_job_event_ready(BlockJob *job);

/**
 * block_job_cancel_sync:
 * @job: The job to be canceled.
 *
 * Synchronously cancel the job.  The completion callback is called
 * before the function returns.  The job may actually complete
 * instead of canceling itself; the circumstances under which this
 * happens depend on the kind of job that is active.
 *
 * Returns the return value from the job if the job actually completed
 * during the call, or -ECANCELED if it was canceled.
 */
int block_job_cancel_sync(BlockJob *job);

/**
 * block_job_cancel_sync_all:
 *
 * Synchronously cancels all jobs using block_job_cancel_sync().
 */
void block_job_cancel_sync_all(void);

/**
 * block_job_complete_sync:
 * @job: The job to be completed.
 * @errp: Error object which may be set by block_job_complete(); this is not
 *        necessarily set on every error, the job return value has to be
 *        checked as well.
 *
 * Synchronously complete the job.  The completion callback is called before the
 * function returns, unless it is NULL (which is permissible when using this
 * function).
 *
 * Returns the return value from the job.
 */
int block_job_complete_sync(BlockJob *job, Error **errp);

/**
 * block_job_iostatus_reset:
 * @job: The job whose I/O status should be reset.
 *
 * Reset I/O status on @job and on BlockDriverState objects it uses,
 * other than job->blk.
 */
void block_job_iostatus_reset(BlockJob *job);

/**
 * block_job_error_action:
 * @job: The job to signal an error for.
 * @on_err: The error action setting.
 * @is_read: Whether the operation was a read.
 * @error: The error that was reported.
 *
 * Report an I/O error for a block job and possibly stop the VM.  Return the
 * action that was selected based on @on_err and @error.
 */
BlockErrorAction block_job_error_action(BlockJob *job, BlockdevOnError on_err,
                                        int is_read, int error);

typedef void BlockJobDeferToMainLoopFn(BlockJob *job, void *opaque);

/**
 * block_job_defer_to_main_loop:
 * @job: The job
 * @fn: The function to run in the main loop
 * @opaque: The opaque value that is passed to @fn
 *
 * Execute a given function in the main loop with the BlockDriverState
 * AioContext acquired.  Block jobs must call bdrv_unref(), bdrv_close(), and
 * anything that uses bdrv_drain_all() in the main loop.
 *
 * The @job AioContext is held while @fn executes.
 */
void block_job_defer_to_main_loop(BlockJob *job,
                                  BlockJobDeferToMainLoopFn *fn,
                                  void *opaque);

/**
 * block_job_txn_new:
 *
 * Allocate and return a new block job transaction.  Jobs can be added to the
 * transaction using block_job_txn_add_job().
 *
 * The transaction is automatically freed when the last job completes or is
 * cancelled.
 *
 * All jobs in the transaction either complete successfully or fail/cancel as a
 * group.  Jobs wait for each other before completing.  Cancelling one job
 * cancels all jobs in the transaction.
 */
BlockJobTxn *block_job_txn_new(void);

/**
 * block_job_txn_unref:
 *
 * Release a reference that was previously acquired with block_job_txn_add_job
 * or block_job_txn_new. If it's the last reference to the object, it will be
 * freed.
 */
void block_job_txn_unref(BlockJobTxn *txn);

/**
 * block_job_txn_add_job:
 * @txn: The transaction (may be NULL)
 * @job: Job to add to the transaction
 *
 * Add @job to the transaction.  The @job must not already be in a transaction.
 * The caller must call either block_job_txn_unref() or block_job_completed()
 * to release the reference that is automatically grabbed here.
 */
void block_job_txn_add_job(BlockJobTxn *txn, BlockJob *job);

#endif