Archipelago » qemu

/*

 * Live block commit

 *

 * Copyright Red Hat, Inc. 2012

 *

 * Authors:

 *  Jeff Cody   <jcody@redhat.com>

 *  Based on stream.c by Stefan Hajnoczi

 *

 * 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/block_int.h"

#include "block/blockjob.h"

#include "qemu/ratelimit.h"

enum {

    /*

     * Size of data buffer for populating the image file.  This should be large

     * enough to process multiple clusters in a single call, so that populating

     * contiguous regions of the image is efficient.

     */

    COMMIT_BUFFER_SIZE = 512 * 1024, /* in bytes */

};

#define SLICE_TIME 100000000ULL /* ns */

typedef struct CommitBlockJob {

    BlockJob common;

    RateLimit limit;

    BlockDriverState *active;

    BlockDriverState *top;

    BlockDriverState *base;

    BlockdevOnError on_error;

    int base_flags;

    int orig_overlay_flags;

} CommitBlockJob;

static int coroutine_fn commit_populate(BlockDriverState *bs,

                                        BlockDriverState *base,

                                        int64_t sector_num, int nb_sectors,

                                        void *buf)

{

    int ret = 0;

    ret = bdrv_read(bs, sector_num, buf, nb_sectors);

    if (ret) {

        return ret;

    }

    ret = bdrv_write(base, sector_num, buf, nb_sectors);

    if (ret) {

        return ret;

    }

    return 0;

}

static void coroutine_fn commit_run(void *opaque)

{

    CommitBlockJob *s = opaque;

    BlockDriverState *active = s->active;

    BlockDriverState *top = s->top;

    BlockDriverState *base = s->base;

    BlockDriverState *overlay_bs;

    int64_t sector_num, end;

    int ret = 0;

    int n = 0;

    void *buf;

    int bytes_written = 0;

    int64_t base_len;

    ret = s->common.len = bdrv_getlength(top);

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

        goto exit_restore_reopen;

    }

    ret = base_len = bdrv_getlength(base);

    if (base_len < 0) {

        goto exit_restore_reopen;

    }

    if (base_len < s->common.len) {

        ret = bdrv_truncate(base, s->common.len);

        if (ret) {

            goto exit_restore_reopen;

        }

    }

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

    buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);

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

        uint64_t delay_ns = 0;

        bool copy;

wait:

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

         * with no pending I/O here so that bdrv_drain_all() returns.

         */

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

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

            break;

        }

        /* Copy if allocated above the base */

        ret = bdrv_co_is_allocated_above(top, base, sector_num,

                                         COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,

                                         &n);

        copy = (ret == 1);

        trace_commit_one_iteration(s, sector_num, n, ret);

        if (copy) {

            if (s->common.speed) {

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

                if (delay_ns > 0) {

                    goto wait;

                }

            }

            ret = commit_populate(top, base, sector_num, n, buf);

            bytes_written += n * BDRV_SECTOR_SIZE;

        }

        if (ret < 0) {

            if (s->on_error == BLOCKDEV_ON_ERROR_STOP ||

                s->on_error == BLOCKDEV_ON_ERROR_REPORT||

                (s->on_error == BLOCKDEV_ON_ERROR_ENOSPC && ret == -ENOSPC)) {

                goto exit_free_buf;

            } else {

                n = 0;

                continue;

            }

        }

        /* Publish progress */

        s->common.offset += n * BDRV_SECTOR_SIZE;

    }

    ret = 0;

    if (!block_job_is_cancelled(&s->common) && sector_num == end) {

        /* success */

        ret = bdrv_drop_intermediate(active, top, base);

    }

exit_free_buf:

    qemu_vfree(buf);

exit_restore_reopen:

    /* restore base open flags here if appropriate (e.g., change the base back

     * to r/o). These reopens do not need to be atomic, since we won't abort

     * even on failure here */

    if (s->base_flags != bdrv_get_flags(base)) {

        bdrv_reopen(base, s->base_flags, NULL);

    }

    overlay_bs = bdrv_find_overlay(active, top);

    if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) {

        bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL);

    }

    block_job_completed(&s->common, ret);

}

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

{

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

    if (speed < 0) {

        error_set(errp, QERR_INVALID_PARAMETER, "speed");

        return;

    }

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

}

static BlockJobType commit_job_type = {

    .instance_size = sizeof(CommitBlockJob),

    .job_type      = "commit",

    .set_speed     = commit_set_speed,

};

void commit_start(BlockDriverState *bs, BlockDriverState *base,

                  BlockDriverState *top, int64_t speed,

                  BlockdevOnError on_error, BlockDriverCompletionFunc *cb,

                  void *opaque, Error **errp)

{

    CommitBlockJob *s;

    BlockReopenQueue *reopen_queue = NULL;

    int orig_overlay_flags;

    int orig_base_flags;

    BlockDriverState *overlay_bs;

    Error *local_err = NULL;

    if ((on_error == BLOCKDEV_ON_ERROR_STOP ||

         on_error == BLOCKDEV_ON_ERROR_ENOSPC) &&

        !bdrv_iostatus_is_enabled(bs)) {

        error_set(errp, QERR_INVALID_PARAMETER_COMBINATION);

        return;

    }

    /* Once we support top == active layer, remove this check */

    if (top == bs) {

        error_setg(errp,

                   "Top image as the active layer is currently unsupported");

        return;

    }

    if (top == base) {

        error_setg(errp, "Invalid files for merge: top and base are the same");

        return;

    }

    overlay_bs = bdrv_find_overlay(bs, top);

    if (overlay_bs == NULL) {

        error_setg(errp, "Could not find overlay image for %s:", top->filename);

        return;

    }

    orig_base_flags    = bdrv_get_flags(base);

    orig_overlay_flags = bdrv_get_flags(overlay_bs);

    /* convert base & overlay_bs to r/w, if necessary */

    if (!(orig_base_flags & BDRV_O_RDWR)) {

        reopen_queue = bdrv_reopen_queue(reopen_queue, base,

                                         orig_base_flags | BDRV_O_RDWR);

    }

    if (!(orig_overlay_flags & BDRV_O_RDWR)) {

        reopen_queue = bdrv_reopen_queue(reopen_queue, overlay_bs,

                                         orig_overlay_flags | BDRV_O_RDWR);

    }

    if (reopen_queue) {

        bdrv_reopen_multiple(reopen_queue, &local_err);

        if (local_err != NULL) {

            error_propagate(errp, local_err);

            return;

        }

    }

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

    if (!s) {

        return;

    }

    s->base   = base;

    s->top    = top;

    s->active = bs;

    s->base_flags          = orig_base_flags;

    s->orig_overlay_flags  = orig_overlay_flags;

    s->on_error = on_error;

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

    trace_commit_start(bs, base, top, s, s->common.co, opaque);

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

}