Archipelago » qemu

/*

 * Image mirroring

 *

 * Copyright Red Hat, Inc. 2012

 *

 * Authors:

 *  Paolo Bonzini  <pbonzini@redhat.com>

 *

 * This work is licensed under the terms of the GNU LGPL, version 2 or later.

 * See the COPYING.LIB file in the top-level directory.

 *

 */

#include "trace.h"

#include "block/blockjob.h"

#include "block/block_int.h"

#include "qemu/ratelimit.h"

#include "qemu/bitmap.h"

#define SLICE_TIME    100000000ULL /* ns */

#define MAX_IN_FLIGHT 16

/* The mirroring buffer is a list of granularity-sized chunks.

 * Free chunks are organized in a list.

 */

typedef struct MirrorBuffer {

    QSIMPLEQ_ENTRY(MirrorBuffer) next;

} MirrorBuffer;

typedef struct MirrorBlockJob {

    BlockJob common;

    RateLimit limit;

    BlockDriverState *target;

    MirrorSyncMode mode;

    BlockdevOnError on_source_error, on_target_error;

    bool synced;

    bool should_complete;

    int64_t sector_num;

    int64_t granularity;

    size_t buf_size;

    unsigned long *cow_bitmap;

    HBitmapIter hbi;

    uint8_t *buf;

    QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;

    int buf_free_count;

    unsigned long *in_flight_bitmap;

    int in_flight;

    int ret;

} MirrorBlockJob;

typedef struct MirrorOp {

    MirrorBlockJob *s;

    QEMUIOVector qiov;

    int64_t sector_num;

    int nb_sectors;

} MirrorOp;

static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,

                                            int error)

{

    s->synced = false;

    if (read) {

        return block_job_error_action(&s->common, s->common.bs,

                                      s->on_source_error, true, error);

    } else {

        return block_job_error_action(&s->common, s->target,

                                      s->on_target_error, false, error);

    }

}

static void mirror_iteration_done(MirrorOp *op, int ret)

{

    MirrorBlockJob *s = op->s;

    struct iovec *iov;

    int64_t chunk_num;

    int i, nb_chunks, sectors_per_chunk;

    trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);

    s->in_flight--;

    iov = op->qiov.iov;

    for (i = 0; i < op->qiov.niov; i++) {

        MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;

        QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);

        s->buf_free_count++;

    }

    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;

    chunk_num = op->sector_num / sectors_per_chunk;

    nb_chunks = op->nb_sectors / sectors_per_chunk;

    bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);

    if (s->cow_bitmap && ret >= 0) {

        bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);

    }

    g_slice_free(MirrorOp, op);

    qemu_coroutine_enter(s->common.co, NULL);

}

static void mirror_write_complete(void *opaque, int ret)

{

    MirrorOp *op = opaque;

    MirrorBlockJob *s = op->s;

    if (ret < 0) {

        BlockDriverState *source = s->common.bs;

        BlockErrorAction action;

        bdrv_set_dirty(source, op->sector_num, op->nb_sectors);

        action = mirror_error_action(s, false, -ret);

        if (action == BDRV_ACTION_REPORT && s->ret >= 0) {

            s->ret = ret;

        }

    }

    mirror_iteration_done(op, ret);

}

static void mirror_read_complete(void *opaque, int ret)

{

    MirrorOp *op = opaque;

    MirrorBlockJob *s = op->s;

    if (ret < 0) {

        BlockDriverState *source = s->common.bs;

        BlockErrorAction action;

        bdrv_set_dirty(source, op->sector_num, op->nb_sectors);

        action = mirror_error_action(s, true, -ret);

        if (action == BDRV_ACTION_REPORT && s->ret >= 0) {

            s->ret = ret;

        }

        mirror_iteration_done(op, ret);

        return;

    }

    bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,

                    mirror_write_complete, op);

}

static void coroutine_fn mirror_iteration(MirrorBlockJob *s)

{

    BlockDriverState *source = s->common.bs;

    int nb_sectors, sectors_per_chunk, nb_chunks;

    int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;

    MirrorOp *op;

    s->sector_num = hbitmap_iter_next(&s->hbi);

    if (s->sector_num < 0) {

        bdrv_dirty_iter_init(source, &s->hbi);

        s->sector_num = hbitmap_iter_next(&s->hbi);

        trace_mirror_restart_iter(s, bdrv_get_dirty_count(source));

        assert(s->sector_num >= 0);

    }

    hbitmap_next_sector = s->sector_num;

    sector_num = s->sector_num;

    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;

    end = s->common.len >> BDRV_SECTOR_BITS;

    /* Extend the QEMUIOVector to include all adjacent blocks that will

     * be copied in this operation.

     *

     * We have to do this if we have no backing file yet in the destination,

     * and the cluster size is very large.  Then we need to do COW ourselves.

     * The first time a cluster is copied, copy it entirely.  Note that,

     * because both the granularity and the cluster size are powers of two,

     * the number of sectors to copy cannot exceed one cluster.

     *

     * We also want to extend the QEMUIOVector to include more adjacent

     * dirty blocks if possible, to limit the number of I/O operations and

     * run efficiently even with a small granularity.

     */

    nb_chunks = 0;

    nb_sectors = 0;

    next_sector = sector_num;

    next_chunk = sector_num / sectors_per_chunk;

    /* Wait for I/O to this cluster (from a previous iteration) to be done.  */

    while (test_bit(next_chunk, s->in_flight_bitmap)) {

        trace_mirror_yield_in_flight(s, sector_num, s->in_flight);

        qemu_coroutine_yield();

    }

    do {

        int added_sectors, added_chunks;

        if (!bdrv_get_dirty(source, next_sector) ||

            test_bit(next_chunk, s->in_flight_bitmap)) {

            assert(nb_sectors > 0);

            break;

        }

        added_sectors = sectors_per_chunk;

        if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {

            bdrv_round_to_clusters(s->target,

                                   next_sector, added_sectors,

                                   &next_sector, &added_sectors);

            /* On the first iteration, the rounding may make us copy

             * sectors before the first dirty one.

             */

            if (next_sector < sector_num) {

                assert(nb_sectors == 0);

                sector_num = next_sector;

                next_chunk = next_sector / sectors_per_chunk;

            }

        }

        added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));

        added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;

        /* When doing COW, it may happen that there is not enough space for

         * a full cluster.  Wait if that is the case.

         */

        while (nb_chunks == 0 && s->buf_free_count < added_chunks) {

            trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);

            qemu_coroutine_yield();

        }

        if (s->buf_free_count < nb_chunks + added_chunks) {

            trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);

            break;

        }

        /* We have enough free space to copy these sectors.  */

        bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);

        nb_sectors += added_sectors;

        nb_chunks += added_chunks;

        next_sector += added_sectors;

        next_chunk += added_chunks;

    } while (next_sector < end);

    /* Allocate a MirrorOp that is used as an AIO callback.  */

    op = g_slice_new(MirrorOp);

    op->s = s;

    op->sector_num = sector_num;

    op->nb_sectors = nb_sectors;

    /* Now make a QEMUIOVector taking enough granularity-sized chunks

     * from s->buf_free.

     */

    qemu_iovec_init(&op->qiov, nb_chunks);

    next_sector = sector_num;

    while (nb_chunks-- > 0) {

        MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);

        QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);

        s->buf_free_count--;

        qemu_iovec_add(&op->qiov, buf, s->granularity);

        /* Advance the HBitmapIter in parallel, so that we do not examine

         * the same sector twice.

         */

        if (next_sector > hbitmap_next_sector && bdrv_get_dirty(source, next_sector)) {

            hbitmap_next_sector = hbitmap_iter_next(&s->hbi);

        }

        next_sector += sectors_per_chunk;

    }

    bdrv_reset_dirty(source, sector_num, nb_sectors);

    /* Copy the dirty cluster.  */

    s->in_flight++;

    trace_mirror_one_iteration(s, sector_num, nb_sectors);

    bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,

                   mirror_read_complete, op);

}

static void mirror_free_init(MirrorBlockJob *s)

{

    int granularity = s->granularity;

    size_t buf_size = s->buf_size;

    uint8_t *buf = s->buf;

    assert(s->buf_free_count == 0);

    QSIMPLEQ_INIT(&s->buf_free);

    while (buf_size != 0) {

        MirrorBuffer *cur = (MirrorBuffer *)buf;

        QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);

        s->buf_free_count++;

        buf_size -= granularity;

        buf += granularity;

    }

}

static void mirror_drain(MirrorBlockJob *s)

{

    while (s->in_flight > 0) {

        qemu_coroutine_yield();

    }

}

static void coroutine_fn mirror_run(void *opaque)

{

    MirrorBlockJob *s = opaque;

    BlockDriverState *bs = s->common.bs;

    int64_t sector_num, end, sectors_per_chunk, length;

    uint64_t last_pause_ns;

    BlockDriverInfo bdi;

    char backing_filename[1024];

    int ret = 0;

    int n;

    if (block_job_is_cancelled(&s->common)) {

        goto immediate_exit;

    }

    s->common.len = bdrv_getlength(bs);

    if (s->common.len <= 0) {

        block_job_completed(&s->common, s->common.len);

        return;

    }

    length = (bdrv_getlength(bs) + s->granularity - 1) / s->granularity;

    s->in_flight_bitmap = bitmap_new(length);

    /* If we have no backing file yet in the destination, we cannot let

     * the destination do COW.  Instead, we copy sectors around the

     * dirty data if needed.  We need a bitmap to do that.

     */

    bdrv_get_backing_filename(s->target, backing_filename,

                              sizeof(backing_filename));

    if (backing_filename[0] && !s->target->backing_hd) {

        bdrv_get_info(s->target, &bdi);

        if (s->granularity < bdi.cluster_size) {

            s->buf_size = MAX(s->buf_size, bdi.cluster_size);

            s->cow_bitmap = bitmap_new(length);

        }

    }

    end = s->common.len >> BDRV_SECTOR_BITS;

    s->buf = qemu_blockalign(bs, s->buf_size);

    sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;

    mirror_free_init(s);

    if (s->mode != MIRROR_SYNC_MODE_NONE) {

        /* First part, loop on the sectors and initialize the dirty bitmap.  */

        BlockDriverState *base;

        base = s->mode == MIRROR_SYNC_MODE_FULL ? NULL : bs->backing_hd;

        for (sector_num = 0; sector_num < end; ) {

            int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;

            ret = bdrv_is_allocated_above(bs, base,

                                          sector_num, next - sector_num, &n);

            if (ret < 0) {

                goto immediate_exit;

            }

            assert(n > 0);

            if (ret == 1) {

                bdrv_set_dirty(bs, sector_num, n);

                sector_num = next;

            } else {

                sector_num += n;

            }

        }

    }

    bdrv_dirty_iter_init(bs, &s->hbi);

    last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);

    for (;;) {

        uint64_t delay_ns;

        int64_t cnt;

        bool should_complete;

        if (s->ret < 0) {

            ret = s->ret;

            goto immediate_exit;

        }

        cnt = bdrv_get_dirty_count(bs);

        /* Note that even when no rate limit is applied we need to yield

         * periodically with no pending I/O so that qemu_aio_flush() returns.

         * We do so every SLICE_TIME nanoseconds, or when there is an error,

         * or when the source is clean, whichever comes first.

         */

        if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME &&

            s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {

            if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||

                (cnt == 0 && s->in_flight > 0)) {

                trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);

                qemu_coroutine_yield();

                continue;

            } else if (cnt != 0) {

                mirror_iteration(s);

                continue;

            }

        }

        should_complete = false;

        if (s->in_flight == 0 && cnt == 0) {

            trace_mirror_before_flush(s);

            ret = bdrv_flush(s->target);

            if (ret < 0) {

                if (mirror_error_action(s, false, -ret) == BDRV_ACTION_REPORT) {

                    goto immediate_exit;

                }

            } else {

                /* We're out of the streaming phase.  From now on, if the job

                 * is cancelled we will actually complete all pending I/O and

                 * report completion.  This way, block-job-cancel will leave

                 * the target in a consistent state.

                 */

                s->common.offset = end * BDRV_SECTOR_SIZE;

                if (!s->synced) {

                    block_job_ready(&s->common);

                    s->synced = true;

                }

                should_complete = s->should_complete ||

                    block_job_is_cancelled(&s->common);

                cnt = bdrv_get_dirty_count(bs);

            }

        }

        if (cnt == 0 && should_complete) {

            /* The dirty bitmap is not updated while operations are pending.

             * If we're about to exit, wait for pending operations before

             * calling bdrv_get_dirty_count(bs), or we may exit while the

             * source has dirty data to copy!

             *

             * Note that I/O can be submitted by the guest while

             * mirror_populate runs.

             */

            trace_mirror_before_drain(s, cnt);

            bdrv_drain_all();

            cnt = bdrv_get_dirty_count(bs);

        }

        ret = 0;

        trace_mirror_before_sleep(s, cnt, s->synced);

        if (!s->synced) {

            /* Publish progress */

            s->common.offset = (end - cnt) * BDRV_SECTOR_SIZE;

            if (s->common.speed) {

                delay_ns = ratelimit_calculate_delay(&s->limit, sectors_per_chunk);

            } else {

                delay_ns = 0;

            }

            block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);

            if (block_job_is_cancelled(&s->common)) {

                break;

            }

        } else if (!should_complete) {

            delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);

            block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);

        } else if (cnt == 0) {

            /* The two disks are in sync.  Exit and report successful

             * completion.

             */

            assert(QLIST_EMPTY(&bs->tracked_requests));

            s->common.cancelled = false;

            break;

        }

        last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);

    }

immediate_exit:

    if (s->in_flight > 0) {

        /* We get here only if something went wrong.  Either the job failed,

         * or it was cancelled prematurely so that we do not guarantee that

         * the target is a copy of the source.

         */

        assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));

        mirror_drain(s);

    }

    assert(s->in_flight == 0);

    qemu_vfree(s->buf);

    g_free(s->cow_bitmap);

    g_free(s->in_flight_bitmap);

    bdrv_set_dirty_tracking(bs, 0);

    bdrv_iostatus_disable(s->target);

    if (s->should_complete && ret == 0) {

        if (bdrv_get_flags(s->target) != bdrv_get_flags(s->common.bs)) {

            bdrv_reopen(s->target, bdrv_get_flags(s->common.bs), NULL);

        }

        bdrv_swap(s->target, s->common.bs);

    }

    bdrv_close(s->target);

    bdrv_unref(s->target);

    block_job_completed(&s->common, ret);

}

static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)

{

    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);

    if (speed < 0) {

        error_set(errp, QERR_INVALID_PARAMETER, "speed");

        return;

    }

    ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);

}

static void mirror_iostatus_reset(BlockJob *job)

{

    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);

    bdrv_iostatus_reset(s->target);

}

static void mirror_complete(BlockJob *job, Error **errp)

{

    MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);

    Error *local_err = NULL;

    int ret;

    ret = bdrv_open_backing_file(s->target, NULL, &local_err);

    if (ret < 0) {

        char backing_filename[PATH_MAX];

        bdrv_get_full_backing_filename(s->target, backing_filename,

                                       sizeof(backing_filename));

        error_propagate(errp, local_err);

        return;

    }

    if (!s->synced) {

        error_set(errp, QERR_BLOCK_JOB_NOT_READY, job->bs->device_name);

        return;

    }

    s->should_complete = true;

    block_job_resume(job);

}

static const BlockJobType mirror_job_type = {

    .instance_size = sizeof(MirrorBlockJob),

    .job_type      = "mirror",

    .set_speed     = mirror_set_speed,

    .iostatus_reset= mirror_iostatus_reset,

    .complete      = mirror_complete,

};

void mirror_start(BlockDriverState *bs, BlockDriverState *target,

                  int64_t speed, int64_t granularity, int64_t buf_size,

                  MirrorSyncMode mode, BlockdevOnError on_source_error,

                  BlockdevOnError on_target_error,

                  BlockDriverCompletionFunc *cb,

                  void *opaque, Error **errp)

{

    MirrorBlockJob *s;

    if (granularity == 0) {

        /* Choose the default granularity based on the target file's cluster

         * size, clamped between 4k and 64k.  */

        BlockDriverInfo bdi;

        if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {

            granularity = MAX(4096, bdi.cluster_size);

            granularity = MIN(65536, granularity);

        } else {

            granularity = 65536;

        }

    }

    assert ((granularity & (granularity - 1)) == 0);

    if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||

         on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&

        !bdrv_iostatus_is_enabled(bs)) {

        error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");

        return;

    }

    s = block_job_create(&mirror_job_type, bs, speed, cb, opaque, errp);

    if (!s) {

        return;

    }

    s->on_source_error = on_source_error;

    s->on_target_error = on_target_error;

    s->target = target;

    s->mode = mode;

    s->granularity = granularity;

    s->buf_size = MAX(buf_size, granularity);

    bdrv_set_dirty_tracking(bs, granularity);

    bdrv_set_enable_write_cache(s->target, true);

    bdrv_set_on_error(s->target, on_target_error, on_target_error);

    bdrv_iostatus_enable(s->target);

    s->common.co = qemu_coroutine_create(mirror_run);

    trace_mirror_start(bs, s, s->common.co, opaque);

    qemu_coroutine_enter(s->common.co, s);

}