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authorFam Zheng <famz@redhat.com>2014-09-11 14:09:56 +0800
committerStefan Hajnoczi <stefanha@redhat.com>2014-09-22 11:39:23 +0100
commite819ab22777fd455d5b130afe48c808d35ef7e93 (patch)
tree7701c3c369c7c9e03e17e84aca651c679b8d67ac /block/null.c
parenta90d411e63ef29bb99b984e0fdb7796aeee1c724 (diff)
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block: Introduce "null" drivers
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: BenoƮt 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>
Diffstat (limited to 'block/null.c')
-rw-r--r--block/null.c168
1 files changed, 168 insertions, 0 deletions
diff --git a/block/null.c b/block/null.c
new file mode 100644
index 0000000..8284419
--- /dev/null
+++ b/block/null.c
@@ -0,0 +1,168 @@
+/*
+ * 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 "block/block_int.h"
+
+typedef struct {
+ int64_t length;
+} BDRVNullState;
+
+static QemuOptsList runtime_opts = {
+ .name = "null",
+ .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+ .desc = {
+ {
+ .name = "filename",
+ .type = QEMU_OPT_STRING,
+ .help = "",
+ },
+ {
+ .name = BLOCK_OPT_SIZE,
+ .type = QEMU_OPT_SIZE,
+ .help = "size of the null block",
+ },
+ { /* end of list */ }
+ },
+};
+
+static int null_file_open(BlockDriverState *bs, QDict *options, int flags,
+ Error **errp)
+{
+ QemuOpts *opts;
+ BDRVNullState *s = bs->opaque;
+
+ 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);
+ qemu_opts_del(opts);
+ return 0;
+}
+
+static void null_close(BlockDriverState *bs)
+{
+}
+
+static int64_t null_getlength(BlockDriverState *bs)
+{
+ BDRVNullState *s = bs->opaque;
+ return s->length;
+}
+
+static coroutine_fn int null_co_readv(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors,
+ QEMUIOVector *qiov)
+{
+ return 0;
+}
+
+static coroutine_fn int null_co_writev(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors,
+ QEMUIOVector *qiov)
+{
+ return 0;
+}
+
+static coroutine_fn int null_co_flush(BlockDriverState *bs)
+{
+ return 0;
+}
+
+typedef struct {
+ BlockDriverAIOCB common;
+ QEMUBH *bh;
+} 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_bh_delete(acb->bh);
+ qemu_aio_unref(acb);
+}
+
+static inline BlockDriverAIOCB *null_aio_common(BlockDriverState *bs,
+ BlockDriverCompletionFunc *cb,
+ void *opaque)
+{
+ NullAIOCB *acb;
+
+ acb = qemu_aio_get(&null_aiocb_info, bs, cb, opaque);
+ acb->bh = aio_bh_new(bdrv_get_aio_context(bs), null_bh_cb, acb);
+ qemu_bh_schedule(acb->bh);
+ return &acb->common;
+}
+
+static BlockDriverAIOCB *null_aio_readv(BlockDriverState *bs,
+ int64_t sector_num, QEMUIOVector *qiov,
+ int nb_sectors,
+ BlockDriverCompletionFunc *cb,
+ void *opaque)
+{
+ return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriverAIOCB *null_aio_writev(BlockDriverState *bs,
+ int64_t sector_num, QEMUIOVector *qiov,
+ int nb_sectors,
+ BlockDriverCompletionFunc *cb,
+ void *opaque)
+{
+ return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriverAIOCB *null_aio_flush(BlockDriverState *bs,
+ BlockDriverCompletionFunc *cb,
+ void *opaque)
+{
+ return null_aio_common(bs, cb, opaque);
+}
+
+static BlockDriver bdrv_null_co = {
+ .format_name = "null-co",
+ .protocol_name = "null-co",
+ .instance_size = sizeof(BDRVNullState),
+
+ .bdrv_file_open = null_file_open,
+ .bdrv_close = null_close,
+ .bdrv_getlength = null_getlength,
+
+ .bdrv_co_readv = null_co_readv,
+ .bdrv_co_writev = null_co_writev,
+ .bdrv_co_flush_to_disk = null_co_flush,
+};
+
+static BlockDriver bdrv_null_aio = {
+ .format_name = "null-aio",
+ .protocol_name = "null-aio",
+ .instance_size = sizeof(BDRVNullState),
+
+ .bdrv_file_open = null_file_open,
+ .bdrv_close = null_close,
+ .bdrv_getlength = null_getlength,
+
+ .bdrv_aio_readv = null_aio_readv,
+ .bdrv_aio_writev = null_aio_writev,
+ .bdrv_aio_flush = null_aio_flush,
+};
+
+static void bdrv_null_init(void)
+{
+ bdrv_register(&bdrv_null_co);
+ bdrv_register(&bdrv_null_aio);
+}
+
+block_init(bdrv_null_init);