replay: introduce block devices record/replay

This patch introduces block driver that implement recording
and replaying of block devices' operations.
All block completion operations are added to the queue.
Queue is flushed at checkpoints and information about processed requests
is recorded to the log. In replay phase the queue is matched with
events read from the log. Therefore block devices requests are processed
deterministically.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
[ kwolf: Rebased onto modified and already applied part of the series ]
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 160 insertions, 0 deletions

diff --git a/block/blkreplay.c b/block/blkreplay.c
new file mode 100755
index 0000000000..42f1813af1
--- /dev/null
+++ b/block/blkreplay.c
@@ -0,0 +1,160 @@
+/*
+ * Block protocol for record/replay
+ *
+ * Copyright (c) 2010-2016 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * 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 "qemu-common.h"
+#include "block/block_int.h"
+#include "sysemu/replay.h"
+#include "qapi/error.h"
+
+typedef struct Request {
+    Coroutine *co;
+    QEMUBH *bh;
+} Request;
+
+/* Next request id.
+   This counter is global, because requests from different
+   block devices should not get overlapping ids. */
+static uint64_t request_id;
+
+static int blkreplay_open(BlockDriverState *bs, QDict *options, int flags,
+                          Error **errp)
+{
+    Error *local_err = NULL;
+    int ret;
+
+    /* Open the image file */
+    bs->file = bdrv_open_child(NULL, options, "image",
+                               bs, &child_file, false, &local_err);
+    if (local_err) {
+        ret = -EINVAL;
+        error_propagate(errp, local_err);
+        goto fail;
+    }
+
+    ret = 0;
+fail:
+    if (ret < 0) {
+        bdrv_unref_child(bs, bs->file);
+    }
+    return ret;
+}
+
+static void blkreplay_close(BlockDriverState *bs)
+{
+}
+
+static int64_t blkreplay_getlength(BlockDriverState *bs)
+{
+    return bdrv_getlength(bs->file->bs);
+}
+
+/* This bh is used for synchronization of return from coroutines.
+   It continues yielded coroutine which then finishes its execution.
+   BH is called adjusted to some replay checkpoint, therefore
+   record and replay will always finish coroutines deterministically.
+*/
+static void blkreplay_bh_cb(void *opaque)
+{
+    Request *req = opaque;
+    qemu_coroutine_enter(req->co, NULL);
+    qemu_bh_delete(req->bh);
+    g_free(req);
+}
+
+static void block_request_create(uint64_t reqid, BlockDriverState *bs,
+                                 Coroutine *co)
+{
+    Request *req = g_new(Request, 1);
+    *req = (Request) {
+        .co = co,
+        .bh = aio_bh_new(bdrv_get_aio_context(bs), blkreplay_bh_cb, req),
+    };
+    replay_block_event(req->bh, reqid);
+}
+
+static int coroutine_fn blkreplay_co_readv(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
+{
+    uint64_t reqid = request_id++;
+    int ret = bdrv_co_readv(bs->file->bs, sector_num, nb_sectors, qiov);
+    block_request_create(reqid, bs, qemu_coroutine_self());
+    qemu_coroutine_yield();
+
+    return ret;
+}
+
+static int coroutine_fn blkreplay_co_writev(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov)
+{
+    uint64_t reqid = request_id++;
+    int ret = bdrv_co_writev(bs->file->bs, sector_num, nb_sectors, qiov);
+    block_request_create(reqid, bs, qemu_coroutine_self());
+    qemu_coroutine_yield();
+
+    return ret;
+}
+
+static int coroutine_fn blkreplay_co_write_zeroes(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
+{
+    uint64_t reqid = request_id++;
+    int ret = bdrv_co_write_zeroes(bs->file->bs, sector_num, nb_sectors, flags);
+    block_request_create(reqid, bs, qemu_coroutine_self());
+    qemu_coroutine_yield();
+
+    return ret;
+}
+
+static int coroutine_fn blkreplay_co_discard(BlockDriverState *bs,
+    int64_t sector_num, int nb_sectors)
+{
+    uint64_t reqid = request_id++;
+    int ret = bdrv_co_discard(bs->file->bs, sector_num, nb_sectors);
+    block_request_create(reqid, bs, qemu_coroutine_self());
+    qemu_coroutine_yield();
+
+    return ret;
+}
+
+static int coroutine_fn blkreplay_co_flush(BlockDriverState *bs)
+{
+    uint64_t reqid = request_id++;
+    int ret = bdrv_co_flush(bs->file->bs);
+    block_request_create(reqid, bs, qemu_coroutine_self());
+    qemu_coroutine_yield();
+
+    return ret;
+}
+
+static BlockDriver bdrv_blkreplay = {
+    .format_name            = "blkreplay",
+    .protocol_name          = "blkreplay",
+    .instance_size          = 0,
+
+    .bdrv_file_open         = blkreplay_open,
+    .bdrv_close             = blkreplay_close,
+    .bdrv_getlength         = blkreplay_getlength,
+
+    .bdrv_co_readv          = blkreplay_co_readv,
+    .bdrv_co_writev         = blkreplay_co_writev,
+
+    .bdrv_co_write_zeroes   = blkreplay_co_write_zeroes,
+    .bdrv_co_discard        = blkreplay_co_discard,
+    .bdrv_co_flush          = blkreplay_co_flush,
+};
+
+static void bdrv_blkreplay_init(void)
+{
+    bdrv_register(&bdrv_blkreplay);
+}
+
+block_init(bdrv_blkreplay_init);