qemu

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/*
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 * QEMU block throttling filter driver infrastructure
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 *
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 * Copyright (c) 2017 Manos Pitsidianakis
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 *
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 * This program is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU General Public License as
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 * published by the Free Software Foundation; either version 2 or
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 * (at your option) version 3 of the License.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, see <http://www.gnu.org/licenses/>.
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 */
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#include "qemu/osdep.h"
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#include "block/block-io.h"
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#include "block/block_int.h"
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#include "block/throttle-groups.h"
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#include "qemu/module.h"
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#include "qemu/option.h"
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#include "qemu/throttle-options.h"
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#include "qapi/error.h"
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static QemuOptsList throttle_opts = {
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    .name = "throttle",
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    .head = QTAILQ_HEAD_INITIALIZER(throttle_opts.head),
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    .desc = {
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        {
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            .name = QEMU_OPT_THROTTLE_GROUP_NAME,
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            .type = QEMU_OPT_STRING,
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            .help = "Name of the throttle group",
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        },
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        { /* end of list */ }
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    },
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};
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/*
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 * If this function succeeds then the throttle group name is stored in
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 * @group and must be freed by the caller.
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 * If there's an error then @group remains unmodified.
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 */
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static int throttle_parse_options(QDict *options, char **group, Error **errp)
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{
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    int ret;
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    const char *group_name;
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    QemuOpts *opts = qemu_opts_create(&throttle_opts, NULL, 0, &error_abort);
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    if (!qemu_opts_absorb_qdict(opts, options, errp)) {
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        ret = -EINVAL;
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        goto fin;
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    }
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    group_name = qemu_opt_get(opts, QEMU_OPT_THROTTLE_GROUP_NAME);
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    if (!group_name) {
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        error_setg(errp, "Please specify a throttle group");
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        ret = -EINVAL;
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        goto fin;
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    } else if (!throttle_group_exists(group_name)) {
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        error_setg(errp, "Throttle group '%s' does not exist", group_name);
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        ret = -EINVAL;
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        goto fin;
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    }
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    *group = g_strdup(group_name);
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    ret = 0;
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fin:
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    qemu_opts_del(opts);
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    return ret;
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}
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static int throttle_open(BlockDriverState *bs, QDict *options,
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                         int flags, Error **errp)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    char *group;
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    int ret;
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    ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
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    if (ret < 0) {
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        return ret;
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    }
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    GRAPH_RDLOCK_GUARD_MAINLOOP();
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    bs->supported_write_flags = bs->file->bs->supported_write_flags |
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                                BDRV_REQ_WRITE_UNCHANGED;
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    bs->supported_zero_flags = bs->file->bs->supported_zero_flags |
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                               BDRV_REQ_WRITE_UNCHANGED;
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    ret = throttle_parse_options(options, &group, errp);
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    if (ret == 0) {
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        /* Register membership to group with name group_name */
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        throttle_group_register_tgm(tgm, group, bdrv_get_aio_context(bs));
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        g_free(group);
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    }
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    return ret;
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}
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static void throttle_close(BlockDriverState *bs)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_unregister_tgm(tgm);
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}
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static int64_t coroutine_fn GRAPH_RDLOCK
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throttle_co_getlength(BlockDriverState *bs)
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{
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    return bdrv_co_getlength(bs->file->bs);
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}
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static int coroutine_fn GRAPH_RDLOCK
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throttle_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
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                   QEMUIOVector *qiov, BdrvRequestFlags flags)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_co_io_limits_intercept(tgm, bytes, THROTTLE_READ);
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    return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
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}
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static int coroutine_fn GRAPH_RDLOCK
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throttle_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
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                    QEMUIOVector *qiov, BdrvRequestFlags flags)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_co_io_limits_intercept(tgm, bytes, THROTTLE_WRITE);
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    return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
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}
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static int coroutine_fn GRAPH_RDLOCK
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throttle_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int64_t bytes,
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                          BdrvRequestFlags flags)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_co_io_limits_intercept(tgm, bytes, THROTTLE_WRITE);
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    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
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}
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static int coroutine_fn GRAPH_RDLOCK
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throttle_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_co_io_limits_intercept(tgm, bytes, THROTTLE_WRITE);
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    return bdrv_co_pdiscard(bs->file, offset, bytes);
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}
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static int coroutine_fn GRAPH_RDLOCK
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throttle_co_pwritev_compressed(BlockDriverState *bs, int64_t offset,
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                               int64_t bytes, QEMUIOVector *qiov)
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{
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    return throttle_co_pwritev(bs, offset, bytes, qiov,
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                               BDRV_REQ_WRITE_COMPRESSED);
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}
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static int coroutine_fn GRAPH_RDLOCK throttle_co_flush(BlockDriverState *bs)
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{
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    return bdrv_co_flush(bs->file->bs);
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}
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static void throttle_detach_aio_context(BlockDriverState *bs)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_detach_aio_context(tgm);
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}
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static void throttle_attach_aio_context(BlockDriverState *bs,
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                                        AioContext *new_context)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    throttle_group_attach_aio_context(tgm, new_context);
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}
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static int throttle_reopen_prepare(BDRVReopenState *reopen_state,
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                                   BlockReopenQueue *queue, Error **errp)
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{
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    int ret;
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    char *group = NULL;
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    assert(reopen_state != NULL);
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    assert(reopen_state->bs != NULL);
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    ret = throttle_parse_options(reopen_state->options, &group, errp);
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    reopen_state->opaque = group;
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    return ret;
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}
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static void throttle_reopen_commit(BDRVReopenState *reopen_state)
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{
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    BlockDriverState *bs = reopen_state->bs;
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    ThrottleGroupMember *tgm = bs->opaque;
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    char *group = reopen_state->opaque;
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    assert(group);
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    if (strcmp(group, throttle_group_get_name(tgm))) {
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        throttle_group_unregister_tgm(tgm);
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        throttle_group_register_tgm(tgm, group, bdrv_get_aio_context(bs));
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    }
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    g_free(reopen_state->opaque);
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    reopen_state->opaque = NULL;
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}
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static void throttle_reopen_abort(BDRVReopenState *reopen_state)
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{
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    g_free(reopen_state->opaque);
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    reopen_state->opaque = NULL;
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}
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static void throttle_drain_begin(BlockDriverState *bs)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    if (qatomic_fetch_inc(&tgm->io_limits_disabled) == 0) {
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        throttle_group_restart_tgm(tgm);
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    }
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}
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static void throttle_drain_end(BlockDriverState *bs)
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{
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    ThrottleGroupMember *tgm = bs->opaque;
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    assert(tgm->io_limits_disabled);
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    qatomic_dec(&tgm->io_limits_disabled);
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}
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static const char *const throttle_strong_runtime_opts[] = {
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    QEMU_OPT_THROTTLE_GROUP_NAME,
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    NULL
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};
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static BlockDriver bdrv_throttle = {
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    .format_name                        =   "throttle",
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    .instance_size                      =   sizeof(ThrottleGroupMember),
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    .bdrv_open                          =   throttle_open,
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    .bdrv_close                         =   throttle_close,
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    .bdrv_co_flush                      =   throttle_co_flush,
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    .bdrv_child_perm                    =   bdrv_default_perms,
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    .bdrv_co_getlength                  =   throttle_co_getlength,
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    .bdrv_co_preadv                     =   throttle_co_preadv,
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    .bdrv_co_pwritev                    =   throttle_co_pwritev,
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    .bdrv_co_pwrite_zeroes              =   throttle_co_pwrite_zeroes,
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    .bdrv_co_pdiscard                   =   throttle_co_pdiscard,
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    .bdrv_co_pwritev_compressed         =   throttle_co_pwritev_compressed,
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    .bdrv_attach_aio_context            =   throttle_attach_aio_context,
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    .bdrv_detach_aio_context            =   throttle_detach_aio_context,
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    .bdrv_reopen_prepare                =   throttle_reopen_prepare,
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    .bdrv_reopen_commit                 =   throttle_reopen_commit,
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    .bdrv_reopen_abort                  =   throttle_reopen_abort,
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    .bdrv_drain_begin                   =   throttle_drain_begin,
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    .bdrv_drain_end                     =   throttle_drain_end,
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    .is_filter                          =   true,
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    .strong_runtime_opts                =   throttle_strong_runtime_opts,
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};
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static void bdrv_throttle_init(void)
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{
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    bdrv_register(&bdrv_throttle);
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}
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block_init(bdrv_throttle_init);
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