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/*
* Image streaming
*
* Copyright IBM, Corp. 2011
*
* Authors:
* Stefan Hajnoczi <stefanha@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"
#include "qemu/ratelimit.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 */
};
#define SLICE_TIME 100000000ULL /* ns */
typedef struct StreamBlockJob {
BlockJob common;
RateLimit limit;
BlockDriverState *base;
char backing_file_id[1024];
} 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_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
}
static void close_unused_images(BlockDriverState *top, BlockDriverState *base,
const char *base_id)
{
BlockDriverState *intermediate;
intermediate = top->backing_hd;
while (intermediate) {
BlockDriverState *unused;
/* reached base */
if (intermediate == base) {
break;
}
unused = intermediate;
intermediate = intermediate->backing_hd;
unused->backing_hd = NULL;
bdrv_delete(unused);
}
top->backing_hd = base;
}
static void coroutine_fn stream_run(void *opaque)
{
StreamBlockJob *s = opaque;
BlockDriverState *bs = s->common.bs;
BlockDriverState *base = s->base;
int64_t sector_num, end;
int ret = 0;
int n = 0;
void *buf;
s->common.len = bdrv_getlength(bs);
if (s->common.len < 0) {
block_job_complete(&s->common, s->common.len);
return;
}
end = s->common.len >> BDRV_SECTOR_BITS;
buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
/* Turn on copy-on-read for the whole block device so that guest read
* requests help us make progress. Only do this when copying the entire
* backing chain since the copy-on-read operation does not take base into
* account.
*/
if (!base) {
bdrv_enable_copy_on_read(bs);
}
for (sector_num = 0; sector_num < end; sector_num += n) {
uint64_t delay_ns = 0;
bool copy;
wait:
/* Note that even when no rate limit is applied we need to yield
* with no pending I/O here so that qemu_aio_flush() returns.
*/
block_job_sleep_ns(&s->common, rt_clock, delay_ns);
if (block_job_is_cancelled(&s->common)) {
break;
}
ret = bdrv_co_is_allocated(bs, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
if (ret == 1) {
/* Allocated in the top, no need to copy. */
copy = false;
} else {
/* Copy if allocated in the intermediate images. Limit to the
* known-unallocated area [sector_num, sector_num+n). */
ret = bdrv_co_is_allocated_above(bs->backing_hd, base,
sector_num, n, &n);
/* Finish early if end of backing file has been reached */
if (ret == 0 && n == 0) {
n = end - sector_num;
}
copy = (ret == 1);
}
trace_stream_one_iteration(s, sector_num, n, ret);
if (ret >= 0 && copy) {
if (s->common.speed) {
delay_ns = ratelimit_calculate_delay(&s->limit, n);
if (delay_ns > 0) {
goto wait;
}
}
ret = stream_populate(bs, sector_num, n, buf);
}
if (ret < 0) {
break;
}
ret = 0;
/* Publish progress */
s->common.offset += n * BDRV_SECTOR_SIZE;
}
if (!base) {
bdrv_disable_copy_on_read(bs);
}
if (!block_job_is_cancelled(&s->common) && sector_num == end && ret == 0) {
const char *base_id = NULL, *base_fmt = NULL;
if (base) {
base_id = s->backing_file_id;
if (base->drv) {
base_fmt = base->drv->format_name;
}
}
ret = bdrv_change_backing_file(bs, base_id, base_fmt);
close_unused_images(bs, base, base_id);
}
qemu_vfree(buf);
block_job_complete(&s->common, ret);
}
static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common);
if (speed < 0) {
error_set(errp, QERR_INVALID_PARAMETER, "speed");
return;
}
ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
}
static BlockJobType stream_job_type = {
.instance_size = sizeof(StreamBlockJob),
.job_type = "stream",
.set_speed = stream_set_speed,
};
void stream_start(BlockDriverState *bs, BlockDriverState *base,
const char *base_id, int64_t speed,
BlockDriverCompletionFunc *cb,
void *opaque, Error **errp)
{
StreamBlockJob *s;
s = block_job_create(&stream_job_type, bs, speed, cb, opaque, errp);
if (!s) {
return;
}
s->base = base;
if (base_id) {
pstrcpy(s->backing_file_id, sizeof(s->backing_file_id), base_id);
}
s->common.co = qemu_coroutine_create(stream_run);
trace_stream_start(bs, base, s, s->common.co, opaque);
qemu_coroutine_enter(s->common.co, s);
}
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