qemu/block/null.c

317 lines
8.8 KiB
C

/*
* Null block driver
*
* Authors:
* Fam Zheng <famz@redhat.com>
*
* Copyright (C) 2014 Red Hat, Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qstring.h"
#include "qemu/module.h"
#include "qemu/option.h"
#include "block/block_int.h"
#define NULL_OPT_LATENCY "latency-ns"
#define NULL_OPT_ZEROES "read-zeroes"
typedef struct {
int64_t length;
int64_t latency_ns;
bool read_zeroes;
} BDRVNullState;
static QemuOptsList runtime_opts = {
.name = "null",
.head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
.desc = {
{
.name = BLOCK_OPT_SIZE,
.type = QEMU_OPT_SIZE,
.help = "size of the null block",
},
{
.name = NULL_OPT_LATENCY,
.type = QEMU_OPT_NUMBER,
.help = "nanoseconds (approximated) to wait "
"before completing request",
},
{
.name = NULL_OPT_ZEROES,
.type = QEMU_OPT_BOOL,
.help = "return zeroes when read",
},
{ /* end of list */ }
},
};
static void null_co_parse_filename(const char *filename, QDict *options,
Error **errp)
{
/* This functions only exists so that a null-co:// filename is accepted
* with the null-co driver. */
if (strcmp(filename, "null-co://")) {
error_setg(errp, "The only allowed filename for this driver is "
"'null-co://'");
return;
}
}
static void null_aio_parse_filename(const char *filename, QDict *options,
Error **errp)
{
/* This functions only exists so that a null-aio:// filename is accepted
* with the null-aio driver. */
if (strcmp(filename, "null-aio://")) {
error_setg(errp, "The only allowed filename for this driver is "
"'null-aio://'");
return;
}
}
static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
QemuOpts *opts;
BDRVNullState *s = bs->opaque;
int ret = 0;
opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
qemu_opts_absorb_qdict(opts, options, &error_abort);
s->length =
qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 1 << 30);
s->latency_ns =
qemu_opt_get_number(opts, NULL_OPT_LATENCY, 0);
if (s->latency_ns < 0) {
error_setg(errp, "latency-ns is invalid");
ret = -EINVAL;
}
s->read_zeroes = qemu_opt_get_bool(opts, NULL_OPT_ZEROES, false);
qemu_opts_del(opts);
bs->supported_write_flags = BDRV_REQ_FUA;
return ret;
}
static int64_t null_getlength(BlockDriverState *bs)
{
BDRVNullState *s = bs->opaque;
return s->length;
}
static coroutine_fn int null_co_common(BlockDriverState *bs)
{
BDRVNullState *s = bs->opaque;
if (s->latency_ns) {
qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, s->latency_ns);
}
return 0;
}
static coroutine_fn int null_co_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
BDRVNullState *s = bs->opaque;
if (s->read_zeroes) {
qemu_iovec_memset(qiov, 0, 0, bytes);
}
return null_co_common(bs);
}
static coroutine_fn int null_co_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
return null_co_common(bs);
}
static coroutine_fn int null_co_flush(BlockDriverState *bs)
{
return null_co_common(bs);
}
typedef struct {
BlockAIOCB common;
QEMUTimer timer;
} NullAIOCB;
static const AIOCBInfo null_aiocb_info = {
.aiocb_size = sizeof(NullAIOCB),
};
static void null_bh_cb(void *opaque)
{
NullAIOCB *acb = opaque;
acb->common.cb(acb->common.opaque, 0);
qemu_aio_unref(acb);
}
static void null_timer_cb(void *opaque)
{
NullAIOCB *acb = opaque;
acb->common.cb(acb->common.opaque, 0);
timer_deinit(&acb->timer);
qemu_aio_unref(acb);
}
static inline BlockAIOCB *null_aio_common(BlockDriverState *bs,
BlockCompletionFunc *cb,
void *opaque)
{
NullAIOCB *acb;
BDRVNullState *s = bs->opaque;
acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
/* Only emulate latency after vcpu is running. */
if (s->latency_ns) {
aio_timer_init(bdrv_get_aio_context(bs), &acb->timer,
QEMU_CLOCK_REALTIME, SCALE_NS,
null_timer_cb, acb);
timer_mod_ns(&acb->timer,
qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + s->latency_ns);
} else {
aio_bh_schedule_oneshot(bdrv_get_aio_context(bs), null_bh_cb, acb);
}
return &acb->common;
}
static BlockAIOCB *null_aio_preadv(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags,
BlockCompletionFunc *cb,
void *opaque)
{
BDRVNullState *s = bs->opaque;
if (s->read_zeroes) {
qemu_iovec_memset(qiov, 0, 0, bytes);
}
return null_aio_common(bs, cb, opaque);
}
static BlockAIOCB *null_aio_pwritev(BlockDriverState *bs,
uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags,
BlockCompletionFunc *cb,
void *opaque)
{
return null_aio_common(bs, cb, opaque);
}
static BlockAIOCB *null_aio_flush(BlockDriverState *bs,
BlockCompletionFunc *cb,
void *opaque)
{
return null_aio_common(bs, cb, opaque);
}
static int null_reopen_prepare(BDRVReopenState *reopen_state,
BlockReopenQueue *queue, Error **errp)
{
return 0;
}
static int coroutine_fn null_co_block_status(BlockDriverState *bs,
bool want_zero, int64_t offset,
int64_t bytes, int64_t *pnum,
int64_t *map,
BlockDriverState **file)
{
BDRVNullState *s = bs->opaque;
int ret = BDRV_BLOCK_OFFSET_VALID;
*pnum = bytes;
*map = offset;
*file = bs;
if (s->read_zeroes) {
ret |= BDRV_BLOCK_ZERO;
}
return ret;
}
static void null_refresh_filename(BlockDriverState *bs)
{
const QDictEntry *e;
for (e = qdict_first(bs->full_open_options); e;
e = qdict_next(bs->full_open_options, e))
{
/* These options can be ignored */
if (strcmp(qdict_entry_key(e), "filename") &&
strcmp(qdict_entry_key(e), "driver") &&
strcmp(qdict_entry_key(e), NULL_OPT_LATENCY))
{
return;
}
}
snprintf(bs->exact_filename, sizeof(bs->exact_filename), "%s://",
bs->drv->format_name);
}
static const char *const null_strong_runtime_opts[] = {
BLOCK_OPT_SIZE,
NULL_OPT_ZEROES,
NULL
};
static BlockDriver bdrv_null_co = {
.format_name = "null-co",
.protocol_name = "null-co",
.instance_size = sizeof(BDRVNullState),
.bdrv_file_open = null_file_open,
.bdrv_parse_filename = null_co_parse_filename,
.bdrv_getlength = null_getlength,
.bdrv_co_preadv = null_co_preadv,
.bdrv_co_pwritev = null_co_pwritev,
.bdrv_co_flush_to_disk = null_co_flush,
.bdrv_reopen_prepare = null_reopen_prepare,
.bdrv_co_block_status = null_co_block_status,
.bdrv_refresh_filename = null_refresh_filename,
.strong_runtime_opts = null_strong_runtime_opts,
};
static BlockDriver bdrv_null_aio = {
.format_name = "null-aio",
.protocol_name = "null-aio",
.instance_size = sizeof(BDRVNullState),
.bdrv_file_open = null_file_open,
.bdrv_parse_filename = null_aio_parse_filename,
.bdrv_getlength = null_getlength,
.bdrv_aio_preadv = null_aio_preadv,
.bdrv_aio_pwritev = null_aio_pwritev,
.bdrv_aio_flush = null_aio_flush,
.bdrv_reopen_prepare = null_reopen_prepare,
.bdrv_co_block_status = null_co_block_status,
.bdrv_refresh_filename = null_refresh_filename,
.strong_runtime_opts = null_strong_runtime_opts,
};
static void bdrv_null_init(void)
{
bdrv_register(&bdrv_null_co);
bdrv_register(&bdrv_null_aio);
}
block_init(bdrv_null_init);