qemu/block/stream.c

283 lines
8.3 KiB
C

/*
* 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 "qemu/osdep.h"
#include "trace.h"
#include "block/block_int.h"
#include "block/blockjob_int.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/ratelimit.h"
#include "sysemu/block-backend.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;
BlockdevOnError on_error;
char *backing_file_str;
int bs_flags;
} StreamBlockJob;
static int coroutine_fn stream_populate(BlockBackend *blk,
int64_t offset, uint64_t bytes,
void *buf)
{
struct iovec iov = {
.iov_base = buf,
.iov_len = bytes,
};
QEMUIOVector qiov;
assert(bytes < SIZE_MAX);
qemu_iovec_init_external(&qiov, &iov, 1);
/* Copy-on-read the unallocated clusters */
return blk_co_preadv(blk, offset, qiov.size, &qiov, BDRV_REQ_COPY_ON_READ);
}
typedef struct {
int ret;
} StreamCompleteData;
static void stream_complete(BlockJob *job, void *opaque)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common);
StreamCompleteData *data = opaque;
BlockDriverState *bs = blk_bs(job->blk);
BlockDriverState *base = s->base;
Error *local_err = NULL;
if (!block_job_is_cancelled(&s->common) && bs->backing &&
data->ret == 0) {
const char *base_id = NULL, *base_fmt = NULL;
if (base) {
base_id = s->backing_file_str;
if (base->drv) {
base_fmt = base->drv->format_name;
}
}
data->ret = bdrv_change_backing_file(bs, base_id, base_fmt);
bdrv_set_backing_hd(bs, base, &local_err);
if (local_err) {
error_report_err(local_err);
data->ret = -EPERM;
goto out;
}
}
out:
/* Reopen the image back in read-only mode if necessary */
if (s->bs_flags != bdrv_get_flags(bs)) {
/* Give up write permissions before making it read-only */
blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort);
bdrv_reopen(bs, s->bs_flags, NULL);
}
g_free(s->backing_file_str);
block_job_completed(&s->common, data->ret);
g_free(data);
}
static void coroutine_fn stream_run(void *opaque)
{
StreamBlockJob *s = opaque;
StreamCompleteData *data;
BlockBackend *blk = s->common.blk;
BlockDriverState *bs = blk_bs(blk);
BlockDriverState *base = s->base;
int64_t offset = 0;
uint64_t delay_ns = 0;
int error = 0;
int ret = 0;
int64_t n = 0; /* bytes */
void *buf;
if (!bs->backing) {
goto out;
}
s->common.len = bdrv_getlength(bs);
if (s->common.len < 0) {
ret = s->common.len;
goto out;
}
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 ( ; offset < s->common.len; offset += n) {
bool copy;
/* Note that even when no rate limit is applied we need to yield
* with no pending I/O here so that bdrv_drain_all() returns.
*/
block_job_sleep_ns(&s->common, delay_ns);
if (block_job_is_cancelled(&s->common)) {
break;
}
copy = false;
ret = bdrv_is_allocated(bs, offset, STREAM_BUFFER_SIZE, &n);
if (ret == 1) {
/* Allocated in the top, no need to copy. */
} else if (ret >= 0) {
/* Copy if allocated in the intermediate images. Limit to the
* known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). */
ret = bdrv_is_allocated_above(backing_bs(bs), base,
offset, n, &n);
/* Finish early if end of backing file has been reached */
if (ret == 0 && n == 0) {
n = s->common.len - offset;
}
copy = (ret == 1);
}
trace_stream_one_iteration(s, offset, n, ret);
if (copy) {
ret = stream_populate(blk, offset, n, buf);
}
if (ret < 0) {
BlockErrorAction action =
block_job_error_action(&s->common, s->on_error, true, -ret);
if (action == BLOCK_ERROR_ACTION_STOP) {
n = 0;
continue;
}
if (error == 0) {
error = ret;
}
if (action == BLOCK_ERROR_ACTION_REPORT) {
break;
}
}
ret = 0;
/* Publish progress */
s->common.offset += n;
if (copy && s->common.speed) {
delay_ns = ratelimit_calculate_delay(&s->limit, n);
} else {
delay_ns = 0;
}
}
if (!base) {
bdrv_disable_copy_on_read(bs);
}
/* Do not remove the backing file if an error was there but ignored. */
ret = error;
qemu_vfree(buf);
out:
/* Modify backing chain and close BDSes in main loop */
data = g_malloc(sizeof(*data));
data->ret = ret;
block_job_defer_to_main_loop(&s->common, stream_complete, data);
}
static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common);
if (speed < 0) {
error_setg(errp, QERR_INVALID_PARAMETER, "speed");
return;
}
ratelimit_set_speed(&s->limit, speed, SLICE_TIME);
}
static const BlockJobDriver stream_job_driver = {
.instance_size = sizeof(StreamBlockJob),
.job_type = BLOCK_JOB_TYPE_STREAM,
.set_speed = stream_set_speed,
.start = stream_run,
};
void stream_start(const char *job_id, BlockDriverState *bs,
BlockDriverState *base, const char *backing_file_str,
int64_t speed, BlockdevOnError on_error, Error **errp)
{
StreamBlockJob *s;
BlockDriverState *iter;
int orig_bs_flags;
/* Make sure that the image is opened in read-write mode */
orig_bs_flags = bdrv_get_flags(bs);
if (!(orig_bs_flags & BDRV_O_RDWR)) {
if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) {
return;
}
}
/* Prevent concurrent jobs trying to modify the graph structure here, we
* already have our own plans. Also don't allow resize as the image size is
* queried only at the job start and then cached. */
s = block_job_create(job_id, &stream_job_driver, NULL, bs,
BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
BLK_PERM_GRAPH_MOD,
BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
BLK_PERM_WRITE,
speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
if (!s) {
goto fail;
}
/* Block all intermediate nodes between bs and base, because they will
* disappear from the chain after this operation. The streaming job reads
* every block only once, assuming that it doesn't change, so block writes
* and resizes. */
for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
&error_abort);
}
s->base = base;
s->backing_file_str = g_strdup(backing_file_str);
s->bs_flags = orig_bs_flags;
s->on_error = on_error;
trace_stream_start(bs, base, s);
block_job_start(&s->common);
return;
fail:
if (orig_bs_flags != bdrv_get_flags(bs)) {
bdrv_reopen(bs, orig_bs_flags, NULL);
}
}