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e819ab2277
This is an analogue to Linux null_blk. It can be used for testing or benchmarking block device emulation and general block layer functionalities such as coroutines and throttling, where disk IO is not necessary or wanted. Use null-aio:// for AIO version, and null-co:// for coroutine version. [Resolved conflict with Fam's async bdrv_aio_cancel() series: 1. Drop .bdrv_aio_cancel() since it is now done by block.c 2. Rename qemu_aio_release() to qemu_aio_unref() --Stefan] Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Benoît Canet <benoit.canet@nodalink.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-id: 1410415798-20673-2-git-send-email-famz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
169 lines
4.5 KiB
C
169 lines
4.5 KiB
C
/*
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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 "block/block_int.h"
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typedef struct {
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int64_t length;
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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 = "filename",
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.type = QEMU_OPT_STRING,
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.help = "",
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},
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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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{ /* end of list */ }
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},
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};
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static int null_file_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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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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qemu_opts_del(opts);
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return 0;
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}
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static void null_close(BlockDriverState *bs)
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{
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}
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static int64_t null_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_readv(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors,
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QEMUIOVector *qiov)
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{
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return 0;
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}
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static coroutine_fn int null_co_writev(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors,
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QEMUIOVector *qiov)
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{
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return 0;
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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 0;
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}
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typedef struct {
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BlockDriverAIOCB common;
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QEMUBH *bh;
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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_bh_delete(acb->bh);
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qemu_aio_unref(acb);
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}
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static inline BlockDriverAIOCB *null_aio_common(BlockDriverState *bs,
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BlockDriverCompletionFunc *cb,
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void *opaque)
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{
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NullAIOCB *acb;
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acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
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acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
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qemu_bh_schedule(acb->bh);
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return &acb->common;
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}
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static BlockDriverAIOCB *null_aio_readv(BlockDriverState *bs,
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int64_t sector_num, QEMUIOVector *qiov,
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int nb_sectors,
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BlockDriverCompletionFunc *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 BlockDriverAIOCB *null_aio_writev(BlockDriverState *bs,
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int64_t sector_num, QEMUIOVector *qiov,
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int nb_sectors,
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BlockDriverCompletionFunc *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 BlockDriverAIOCB *null_aio_flush(BlockDriverState *bs,
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BlockDriverCompletionFunc *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 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_file_open = null_file_open,
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.bdrv_close = null_close,
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.bdrv_getlength = null_getlength,
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.bdrv_co_readv = null_co_readv,
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.bdrv_co_writev = null_co_writev,
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.bdrv_co_flush_to_disk = null_co_flush,
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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_file_open = null_file_open,
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.bdrv_close = null_close,
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.bdrv_getlength = null_getlength,
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.bdrv_aio_readv = null_aio_readv,
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.bdrv_aio_writev = null_aio_writev,
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.bdrv_aio_flush = null_aio_flush,
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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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