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51b0a48888
We are gradually moving away from sector-based interfaces, towards byte-based. In the common case, allocation is unlikely to ever use values that are not naturally sector-aligned, but it is possible that byte-based values will let us be more precise about allocation at the end of an unaligned file that can do byte-based access. Changing the signature of the function to use int64_t *pnum ensures that the compiler enforces that all callers are updated. For now, the io.c layer still assert()s that all callers are sector-aligned, but that can be relaxed when a later patch implements byte-based block status. Therefore, for the most part this patch is just the addition of scaling at the callers followed by inverse scaling at bdrv_is_allocated(). But some code, particularly stream_run(), gets a lot simpler because it no longer has to mess with sectors. Leave comments where we can further simplify by switching to byte-based iterations, once later patches eliminate the need for sector-aligned operations. For ease of review, bdrv_is_allocated() was tackled separately. Signed-off-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
281 lines
8.3 KiB
C
281 lines
8.3 KiB
C
/*
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* Image streaming
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "trace.h"
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#include "block/block_int.h"
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#include "block/blockjob_int.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qerror.h"
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#include "qemu/ratelimit.h"
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#include "sysemu/block-backend.h"
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enum {
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/*
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* Size of data buffer for populating the image file. This should be large
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* enough to process multiple clusters in a single call, so that populating
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* contiguous regions of the image is efficient.
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*/
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STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
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};
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#define SLICE_TIME 100000000ULL /* ns */
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typedef struct StreamBlockJob {
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BlockJob common;
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RateLimit limit;
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BlockDriverState *base;
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BlockdevOnError on_error;
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char *backing_file_str;
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int bs_flags;
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} StreamBlockJob;
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static int coroutine_fn stream_populate(BlockBackend *blk,
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int64_t offset, uint64_t bytes,
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void *buf)
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{
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struct iovec iov = {
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.iov_base = buf,
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.iov_len = bytes,
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};
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QEMUIOVector qiov;
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assert(bytes < SIZE_MAX);
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qemu_iovec_init_external(&qiov, &iov, 1);
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/* Copy-on-read the unallocated clusters */
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return blk_co_preadv(blk, offset, qiov.size, &qiov, BDRV_REQ_COPY_ON_READ);
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}
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typedef struct {
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int ret;
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} StreamCompleteData;
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static void stream_complete(BlockJob *job, void *opaque)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common);
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StreamCompleteData *data = opaque;
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BlockDriverState *bs = blk_bs(job->blk);
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BlockDriverState *base = s->base;
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Error *local_err = NULL;
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if (!block_job_is_cancelled(&s->common) && bs->backing &&
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data->ret == 0) {
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const char *base_id = NULL, *base_fmt = NULL;
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if (base) {
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base_id = s->backing_file_str;
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if (base->drv) {
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base_fmt = base->drv->format_name;
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}
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}
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data->ret = bdrv_change_backing_file(bs, base_id, base_fmt);
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bdrv_set_backing_hd(bs, base, &local_err);
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if (local_err) {
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error_report_err(local_err);
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data->ret = -EPERM;
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goto out;
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}
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}
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out:
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/* Reopen the image back in read-only mode if necessary */
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if (s->bs_flags != bdrv_get_flags(bs)) {
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/* Give up write permissions before making it read-only */
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blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort);
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bdrv_reopen(bs, s->bs_flags, NULL);
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}
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g_free(s->backing_file_str);
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block_job_completed(&s->common, data->ret);
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g_free(data);
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}
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static void coroutine_fn stream_run(void *opaque)
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{
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StreamBlockJob *s = opaque;
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StreamCompleteData *data;
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BlockBackend *blk = s->common.blk;
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BlockDriverState *bs = blk_bs(blk);
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BlockDriverState *base = s->base;
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int64_t offset = 0;
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uint64_t delay_ns = 0;
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int error = 0;
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int ret = 0;
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int64_t n = 0; /* bytes */
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void *buf;
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if (!bs->backing) {
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goto out;
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}
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s->common.len = bdrv_getlength(bs);
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if (s->common.len < 0) {
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ret = s->common.len;
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goto out;
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}
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buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
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/* Turn on copy-on-read for the whole block device so that guest read
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* requests help us make progress. Only do this when copying the entire
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* backing chain since the copy-on-read operation does not take base into
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* account.
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*/
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if (!base) {
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bdrv_enable_copy_on_read(bs);
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}
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for ( ; offset < s->common.len; offset += n) {
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bool copy;
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/* Note that even when no rate limit is applied we need to yield
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* with no pending I/O here so that bdrv_drain_all() returns.
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*/
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block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
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if (block_job_is_cancelled(&s->common)) {
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break;
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}
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copy = false;
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ret = bdrv_is_allocated(bs, offset, STREAM_BUFFER_SIZE, &n);
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if (ret == 1) {
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/* Allocated in the top, no need to copy. */
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} else if (ret >= 0) {
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/* Copy if allocated in the intermediate images. Limit to the
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* known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE). */
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ret = bdrv_is_allocated_above(backing_bs(bs), base,
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offset, n, &n);
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/* Finish early if end of backing file has been reached */
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if (ret == 0 && n == 0) {
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n = s->common.len - offset;
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}
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copy = (ret == 1);
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}
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trace_stream_one_iteration(s, offset, n, ret);
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if (copy) {
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ret = stream_populate(blk, offset, n, buf);
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}
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if (ret < 0) {
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BlockErrorAction action =
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block_job_error_action(&s->common, s->on_error, true, -ret);
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if (action == BLOCK_ERROR_ACTION_STOP) {
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n = 0;
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continue;
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}
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if (error == 0) {
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error = ret;
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}
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if (action == BLOCK_ERROR_ACTION_REPORT) {
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break;
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}
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}
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ret = 0;
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/* Publish progress */
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s->common.offset += n;
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if (copy && s->common.speed) {
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delay_ns = ratelimit_calculate_delay(&s->limit, n);
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}
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}
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if (!base) {
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bdrv_disable_copy_on_read(bs);
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}
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/* Do not remove the backing file if an error was there but ignored. */
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ret = error;
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qemu_vfree(buf);
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out:
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/* Modify backing chain and close BDSes in main loop */
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data = g_malloc(sizeof(*data));
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data->ret = ret;
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block_job_defer_to_main_loop(&s->common, stream_complete, data);
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}
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static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common);
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if (speed < 0) {
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error_setg(errp, QERR_INVALID_PARAMETER, "speed");
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return;
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}
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ratelimit_set_speed(&s->limit, speed, SLICE_TIME);
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}
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static const BlockJobDriver stream_job_driver = {
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.instance_size = sizeof(StreamBlockJob),
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.job_type = BLOCK_JOB_TYPE_STREAM,
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.set_speed = stream_set_speed,
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.start = stream_run,
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};
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void stream_start(const char *job_id, BlockDriverState *bs,
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BlockDriverState *base, const char *backing_file_str,
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int64_t speed, BlockdevOnError on_error, Error **errp)
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{
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StreamBlockJob *s;
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BlockDriverState *iter;
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int orig_bs_flags;
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/* Make sure that the image is opened in read-write mode */
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orig_bs_flags = bdrv_get_flags(bs);
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if (!(orig_bs_flags & BDRV_O_RDWR)) {
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if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) {
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return;
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}
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}
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/* Prevent concurrent jobs trying to modify the graph structure here, we
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* already have our own plans. Also don't allow resize as the image size is
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* queried only at the job start and then cached. */
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s = block_job_create(job_id, &stream_job_driver, bs,
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BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
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BLK_PERM_GRAPH_MOD,
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BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
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BLK_PERM_WRITE,
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speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
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if (!s) {
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goto fail;
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}
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/* Block all intermediate nodes between bs and base, because they will
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* disappear from the chain after this operation. The streaming job reads
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* every block only once, assuming that it doesn't change, so block writes
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* and resizes. */
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for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
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block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
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BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
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&error_abort);
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}
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s->base = base;
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s->backing_file_str = g_strdup(backing_file_str);
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s->bs_flags = orig_bs_flags;
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s->on_error = on_error;
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trace_stream_start(bs, base, s);
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block_job_start(&s->common);
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return;
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fail:
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if (orig_bs_flags != bdrv_get_flags(bs)) {
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bdrv_reopen(bs, orig_bs_flags, NULL);
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}
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}
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