This patch allows using '-snapshot' behavior in record/replay mode. blkreplay layer creates temporary overlays on top of underlaying disk images. It is needed, because creating an overlay over blkreplay breaks the determinism.
Signed-off-by: Pavel Dovgalyuk <pavel.dovga...@ispras.ru> --- block/blkreplay.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++ stubs/replay.c | 1 + vl.c | 2 + 3 files changed, 78 insertions(+), 1 deletion(-) diff --git a/block/blkreplay.c b/block/blkreplay.c index 8a03d62..172642f 100644 --- a/block/blkreplay.c +++ b/block/blkreplay.c @@ -14,12 +14,76 @@ #include "block/block_int.h" #include "sysemu/replay.h" #include "qapi/error.h" +#include "qapi/qmp/qstring.h" typedef struct Request { Coroutine *co; QEMUBH *bh; } Request; +static BlockDriverState *blkreplay_append_snapshot(BlockDriverState *bs, + Error **errp) +{ + int ret; + BlockDriverState *bs_snapshot; + int64_t total_size; + QemuOpts *opts = NULL; + char tmp_filename[PATH_MAX + 1]; + QDict *snapshot_options = qdict_new(); + + /* Prepare options QDict for the overlay file */ + qdict_put(snapshot_options, "file.driver", + qstring_from_str("file")); + qdict_put(snapshot_options, "driver", + qstring_from_str("qcow2")); + + /* Create temporary file */ + ret = get_tmp_filename(tmp_filename, PATH_MAX + 1); + if (ret < 0) { + error_setg_errno(errp, -ret, "Could not get temporary filename"); + goto out; + } + qdict_put(snapshot_options, "file.filename", + qstring_from_str(tmp_filename)); + + /* Get the required size from the image */ + total_size = bdrv_getlength(bs); + if (total_size < 0) { + error_setg_errno(errp, -total_size, "Could not get image size"); + goto out; + } + + opts = qemu_opts_create(bdrv_qcow2.create_opts, NULL, 0, &error_abort); + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, total_size, &error_abort); + ret = bdrv_create(&bdrv_qcow2, tmp_filename, opts, errp); + qemu_opts_del(opts); + if (ret < 0) { + error_prepend(errp, "Could not create temporary overlay '%s': ", + tmp_filename); + goto out; + } + + bs_snapshot = bdrv_open(NULL, NULL, snapshot_options, + BDRV_O_RDWR | BDRV_O_TEMPORARY, errp); + snapshot_options = NULL; + if (!bs_snapshot) { + ret = -EINVAL; + goto out; + } + + /* bdrv_append() consumes a strong reference to bs_snapshot (i.e. it will + * call bdrv_unref() on it), so in order to be able to return one, we have + * to increase bs_snapshot's refcount here */ + bdrv_ref(bs_snapshot); + bdrv_append(bs_snapshot, bs); + + return bs_snapshot; + +out: + QDECREF(snapshot_options); + return NULL; +} + static int blkreplay_open(BlockDriverState *bs, QDict *options, int flags, Error **errp) { @@ -35,6 +99,14 @@ static int blkreplay_open(BlockDriverState *bs, QDict *options, int flags, goto fail; } + /* Add temporary snapshot to preserve the image */ + if (!replay_snapshot + && !blkreplay_append_snapshot(bs->file->bs, &local_err)) { + ret = -EINVAL; + error_propagate(errp, local_err); + goto fail; + } + ret = 0; fail: if (ret < 0) { @@ -45,6 +117,10 @@ fail: static void blkreplay_close(BlockDriverState *bs) { + if (!replay_snapshot) { + /* Unref created snapshot file */ + bdrv_unref(bs->file->bs); + } } static int64_t blkreplay_getlength(BlockDriverState *bs) diff --git a/stubs/replay.c b/stubs/replay.c index d9a6da9..e43e467 100644 --- a/stubs/replay.c +++ b/stubs/replay.c @@ -3,6 +3,7 @@ #include "sysemu/sysemu.h" ReplayMode replay_mode; +char *replay_snapshot; int64_t replay_save_clock(unsigned int kind, int64_t clock) { diff --git a/vl.c b/vl.c index 52a6ac8..def0520 100644 --- a/vl.c +++ b/vl.c @@ -4474,7 +4474,7 @@ int main(int argc, char **argv, char **envp) } /* open the virtual block devices */ - if (snapshot || replay_mode != REPLAY_MODE_NONE) { + if (snapshot) { qemu_opts_foreach(qemu_find_opts("drive"), drive_enable_snapshot, NULL, NULL); }