On Thu, Oct 27, 2011 at 04:22:50PM +0100, Stefan Hajnoczi wrote:
> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> ---
> Makefile.objs | 1 +
> block/stream.c | 135
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> block_int.h | 3 +
> trace-events | 4 ++
> 4 files changed, 143 insertions(+), 0 deletions(-)
> create mode 100644 block/stream.c
>
> diff --git a/Makefile.objs b/Makefile.objs
> index c290fd3..802db96 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -34,6 +34,7 @@ block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o
> qcow2-snapshot.o qcow
> block-nested-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
> block-nested-y += qed-check.o
> block-nested-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
> +block-nested-y += stream.o
> block-nested-$(CONFIG_WIN32) += raw-win32.o
> block-nested-$(CONFIG_POSIX) += raw-posix.o
> block-nested-$(CONFIG_CURL) += curl.o
> diff --git a/block/stream.c b/block/stream.c
> new file mode 100644
> index 0000000..8cdf566
> --- /dev/null
> +++ b/block/stream.c
> @@ -0,0 +1,135 @@
> +/*
> + * Image streaming
> + *
> + * Copyright IBM, Corp. 2011
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2 or later.
> + * See the COPYING.LIB file in the top-level directory.
> + *
> + */
> +
> +#include "trace.h"
> +#include "block_int.h"
> +
> +enum {
> + /*
> + * Size of data buffer for populating the image file. This should be
> large
> + * enough to process multiple clusters in a single call, so that
> populating
> + * contiguous regions of the image is efficient.
> + */
> + STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
> +};
> +
> +typedef struct StreamBlockJob {
> + BlockJob common;
> + BlockDriverState *base;
> +} StreamBlockJob;
> +
> +static int coroutine_fn stream_populate(BlockDriverState *bs,
> + int64_t sector_num, int nb_sectors,
> + void *buf)
> +{
> + struct iovec iov = {
> + .iov_base = buf,
> + .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
> + };
> + QEMUIOVector qiov;
> +
> + qemu_iovec_init_external(&qiov, &iov, 1);
> +
> + /* Copy-on-read the unallocated clusters */
> + return bdrv_co_readv(bs, sector_num, nb_sectors, &qiov);
> +}
> +
> +static int stream_one_iteration(StreamBlockJob *s, int64_t sector_num,
> + void *buf, int max_sectors, int *n)
> +{
> + BlockDriverState *bs = s->common.bs;
> + int ret;
> +
> + trace_stream_one_iteration(s, sector_num, max_sectors);
> +
> + ret = bdrv_is_allocated(bs, sector_num, max_sectors, n);
> + if (ret < 0) {
> + return ret;
> + }
bdrv_is_allocated is still synchronous? If so, there should be at least
a plan to make it asynchronous.
> + if (!ret) {
> + ret = stream_populate(bs, sector_num, *n, buf);
> + }
> + return ret;
> +}
> +
> +static void coroutine_fn stream_run(void *opaque)
> +{
> + StreamBlockJob *s = opaque;
> + BlockDriverState *bs = s->common.bs;
> + int64_t sector_num, end;
> + int ret = 0;
> + int n;
> + void *buf;
> +
> + buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
> + s->common.len = bdrv_getlength(bs);
> + bdrv_get_geometry(bs, (uint64_t *)&end);
> +
> + bdrv_set_zero_detection(bs, true);
> + bdrv_set_copy_on_read(bs, true);
Should distinguish between stream initiated and user initiated setting
of zero detection and cor (so that unsetting below does not clear
user settings).
> +
> + for (sector_num = 0; sector_num < end; sector_num += n) {
> + if (block_job_is_cancelled(&s->common)) {
> + break;
> + }
If cancellation is seen here in the last loop iteration,
bdrv_change_backing_file below should not be executed.
> +
> + /* TODO rate-limit */
> + /* Note that even when no rate limit is applied we need to yield with
> + * no pending I/O here so that qemu_aio_flush() is able to return.
> + */
> + co_sleep_ns(rt_clock, 0);
How do you plan to implement rate limit?
> +
> + ret = stream_one_iteration(s, sector_num, buf,
> + STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE,
> &n);
> + if (ret < 0) {
> + break;
> + }
> +
> + /* Publish progress */
> + s->common.offset += n * BDRV_SECTOR_SIZE;
> + }
> +
> + bdrv_set_copy_on_read(bs, false);
> + bdrv_set_zero_detection(bs, false);
> +
> + if (sector_num == end && ret == 0) {
> + bdrv_change_backing_file(bs, NULL, NULL);
> + }
> +
> + qemu_vfree(buf);
> + block_job_complete(&s->common, ret);
> +}
> +
> +static BlockJobType stream_job_type = {
> + .instance_size = sizeof(StreamBlockJob),
> + .job_type = "stream",
> +};
> +
> +int stream_start(BlockDriverState *bs, BlockDriverState *base,
> + BlockDriverCompletionFunc *cb, void *opaque)
> +{
> + StreamBlockJob *s;
> + Coroutine *co;
> +
> + if (bs->job) {
> + return -EBUSY;
> + }
> +
> + s = block_job_create(&stream_job_type, bs, cb, opaque);
> + s->base = base;
> +
> + co = qemu_coroutine_create(stream_run);
> + trace_stream_start(bs, base, s, co, opaque);
> + qemu_coroutine_enter(co, s);
> + return 0;
> +}
I'd like to see the shared base code implemented before this is merged.
On a related note, the maze of coroutine locks and waiting queues makes
it difficult to have a clear picture of the execution flow (perhaps that
is due to lack of familiarity with the use of coroutines in the block
code).
