qemu

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/*
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 * Null block driver
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 *
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 * Authors:
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 *  Fam Zheng <famz@redhat.com>
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 *
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 * Copyright (C) 2014 Red Hat, Inc.
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 *
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 * This work is licensed under the terms of the GNU GPL, version 2 or later.
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 * See the COPYING file in the top-level directory.
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 */
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qdict.h"
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#include "qapi/qmp/qstring.h"
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#include "qemu/module.h"
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#include "qemu/option.h"
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#include "block/block-io.h"
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#include "block/block_int.h"
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#include "sysemu/replay.h"
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#define NULL_OPT_LATENCY "latency-ns"
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#define NULL_OPT_ZEROES  "read-zeroes"
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typedef struct {
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    int64_t length;
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    int64_t latency_ns;
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    bool read_zeroes;
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} BDRVNullState;
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static QemuOptsList runtime_opts = {
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    .name = "null",
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    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
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    .desc = {
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        {
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            .name = BLOCK_OPT_SIZE,
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            .type = QEMU_OPT_SIZE,
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            .help = "size of the null block",
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        },
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        {
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            .name = NULL_OPT_LATENCY,
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            .type = QEMU_OPT_NUMBER,
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            .help = "nanoseconds (approximated) to wait "
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                    "before completing request",
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        },
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        {
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            .name = NULL_OPT_ZEROES,
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            .type = QEMU_OPT_BOOL,
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            .help = "return zeroes when read",
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        },
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        { /* end of list */ }
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    },
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};
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static void null_co_parse_filename(const char *filename, QDict *options,
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                                   Error **errp)
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{
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    /* This functions only exists so that a null-co:// filename is accepted
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     * with the null-co driver. */
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    if (strcmp(filename, "null-co://")) {
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        error_setg(errp, "The only allowed filename for this driver is "
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                         "'null-co://'");
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        return;
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    }
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}
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static void null_aio_parse_filename(const char *filename, QDict *options,
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                                    Error **errp)
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{
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    /* This functions only exists so that a null-aio:// filename is accepted
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     * with the null-aio driver. */
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    if (strcmp(filename, "null-aio://")) {
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        error_setg(errp, "The only allowed filename for this driver is "
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                         "'null-aio://'");
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        return;
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    }
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}
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static int null_open(BlockDriverState *bs, QDict *options, int flags,
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                     Error **errp)
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{
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    QemuOpts *opts;
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    BDRVNullState *s = bs->opaque;
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    int ret = 0;
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    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
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    qemu_opts_absorb_qdict(opts, options, &error_abort);
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    s->length =
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        qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
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    s->latency_ns =
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        qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
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    if (s->latency_ns < 0) {
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        error_setg(errp, "latency-ns is invalid");
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        ret = -EINVAL;
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    }
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    s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false);
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    qemu_opts_del(opts);
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    bs->supported_write_flags = BDRV_REQ_FUA;
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    return ret;
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}
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static int64_t coroutine_fn null_co_getlength(BlockDriverState *bs)
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{
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    BDRVNullState *s = bs->opaque;
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    return s->length;
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}
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static coroutine_fn int null_co_common(BlockDriverState *bs)
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{
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    BDRVNullState *s = bs->opaque;
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    if (s->latency_ns) {
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        qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns);
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    }
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    return 0;
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}
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static coroutine_fn int null_co_preadv(BlockDriverState *bs,
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                                       int64_t offset, int64_t bytes,
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                                       QEMUIOVector *qiov,
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                                       BdrvRequestFlags flags)
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{
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    BDRVNullState *s = bs->opaque;
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    if (s->read_zeroes) {
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        qemu_iovec_memset(qiov, 0, 0, bytes);
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    }
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    return null_co_common(bs);
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}
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static coroutine_fn int null_co_pwritev(BlockDriverState *bs,
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                                        int64_t offset, int64_t bytes,
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                                        QEMUIOVector *qiov,
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                                        BdrvRequestFlags flags)
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{
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    return null_co_common(bs);
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}
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static coroutine_fn int null_co_flush(BlockDriverState *bs)
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{
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    return null_co_common(bs);
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}
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typedef struct {
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    BlockAIOCB common;
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    QEMUTimer timer;
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} NullAIOCB;
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static const AIOCBInfo null_aiocb_info = {
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    .aiocb_size = sizeof(NullAIOCB),
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};
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static void null_bh_cb(void *opaque)
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{
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    NullAIOCB *acb = opaque;
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    acb->common.cb(acb->common.opaque, 0);
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    qemu_aio_unref(acb);
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}
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static void null_timer_cb(void *opaque)
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{
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    NullAIOCB *acb = opaque;
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    acb->common.cb(acb->common.opaque, 0);
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    timer_deinit(&acb->timer);
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    qemu_aio_unref(acb);
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}
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static inline BlockAIOCB *null_aio_common(BlockDriverState *bs,
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                                          BlockCompletionFunc *cb,
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                                          void *opaque)
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{
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    NullAIOCB *acb;
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    BDRVNullState *s = bs->opaque;
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    acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
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    /* Only emulate latency after vcpu is running. */
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    if (s->latency_ns) {
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        aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
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                       QEMU_CLOCK_REALTIME, SCALE_NS,
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                       null_timer_cb, acb);
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        timer_mod_ns(&acb->timer,
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                     qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns);
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    } else {
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        replay_bh_schedule_oneshot_event(bdrv_get_aio_context(bs),
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                                         null_bh_cb, acb);
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    }
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    return &acb->common;
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}
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static BlockAIOCB *null_aio_preadv(BlockDriverState *bs,
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                                   int64_t offset, int64_t bytes,
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                                   QEMUIOVector *qiov, BdrvRequestFlags flags,
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                                   BlockCompletionFunc *cb,
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                                   void *opaque)
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{
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    BDRVNullState *s = bs->opaque;
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    if (s->read_zeroes) {
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        qemu_iovec_memset(qiov, 0, 0, bytes);
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    }
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    return null_aio_common(bs, cb, opaque);
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}
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static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs,
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                                    int64_t offset, int64_t bytes,
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                                    QEMUIOVector *qiov, BdrvRequestFlags flags,
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                                    BlockCompletionFunc *cb,
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                                    void *opaque)
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{
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    return null_aio_common(bs, cb, opaque);
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}
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static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
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                                  BlockCompletionFunc *cb,
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                                  void *opaque)
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{
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    return null_aio_common(bs, cb, opaque);
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}
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static int null_reopen_prepare(BDRVReopenState *reopen_state,
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                               BlockReopenQueue *queue, Error **errp)
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{
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    return 0;
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}
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static int coroutine_fn null_co_block_status(BlockDriverState *bs,
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                                             bool want_zero, int64_t offset,
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                                             int64_t bytes, int64_t *pnum,
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                                             int64_t *map,
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                                             BlockDriverState **file)
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{
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    BDRVNullState *s = bs->opaque;
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    int ret = BDRV_BLOCK_OFFSET_VALID;
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    *pnum = bytes;
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    *map = offset;
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    *file = bs;
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    if (s->read_zeroes) {
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        ret |= BDRV_BLOCK_ZERO;
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    }
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    return ret;
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}
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static void null_refresh_filename(BlockDriverState *bs)
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{
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    const QDictEntry *e;
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    for (e = qdict_first(bs->full_open_options); e;
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         e = qdict_next(bs->full_open_options, e))
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    {
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        /* These options can be ignored */
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        if (strcmp(qdict_entry_key(e), "filename") &&
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            strcmp(qdict_entry_key(e), "driver") &&
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            strcmp(qdict_entry_key(e), NULL_OPT_LATENCY))
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        {
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            return;
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        }
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    }
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    snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://",
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             bs->drv->format_name);
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}
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static int64_t coroutine_fn
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null_co_get_allocated_file_size(BlockDriverState *bs)
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{
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    return 0;
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}
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static const char *const null_strong_runtime_opts[] = {
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    BLOCK_OPT_SIZE,
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    NULL_OPT_ZEROES,
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    NULL
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};
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static BlockDriver bdrv_null_co = {
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    .format_name            = "null-co",
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    .protocol_name          = "null-co",
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    .instance_size          = sizeof(BDRVNullState),
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    .bdrv_open              = null_open,
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    .bdrv_parse_filename    = null_co_parse_filename,
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    .bdrv_co_getlength      = null_co_getlength,
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    .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size,
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    .bdrv_co_preadv         = null_co_preadv,
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    .bdrv_co_pwritev        = null_co_pwritev,
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    .bdrv_co_flush_to_disk  = null_co_flush,
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    .bdrv_reopen_prepare    = null_reopen_prepare,
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    .bdrv_co_block_status   = null_co_block_status,
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    .bdrv_refresh_filename  = null_refresh_filename,
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    .strong_runtime_opts    = null_strong_runtime_opts,
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};
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static BlockDriver bdrv_null_aio = {
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    .format_name            = "null-aio",
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    .protocol_name          = "null-aio",
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    .instance_size          = sizeof(BDRVNullState),
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    .bdrv_open              = null_open,
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    .bdrv_parse_filename    = null_aio_parse_filename,
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    .bdrv_co_getlength      = null_co_getlength,
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    .bdrv_co_get_allocated_file_size = null_co_get_allocated_file_size,
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    .bdrv_aio_preadv        = null_aio_preadv,
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    .bdrv_aio_pwritev       = null_aio_pwritev,
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    .bdrv_aio_flush         = null_aio_flush,
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    .bdrv_reopen_prepare    = null_reopen_prepare,
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    .bdrv_co_block_status   = null_co_block_status,
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    .bdrv_refresh_filename  = null_refresh_filename,
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    .strong_runtime_opts    = null_strong_runtime_opts,
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};
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static void bdrv_null_init(void)
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{
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    bdrv_register(&bdrv_null_co);
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    bdrv_register(&bdrv_null_aio);
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}
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block_init(bdrv_null_init);
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