281 lines
8.4 KiB
C
281 lines
8.4 KiB
C
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/*
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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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* Maximum chunk size to feed to copy-on-read. This should be
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* large enough to process multiple clusters in a single call, so
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* that populating contiguous regions of the image is efficient.
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*/
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STREAM_CHUNK = 512 * 1024, /* in bytes */
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};
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typedef struct StreamBlockJob {
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BlockJob common;
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BlockDriverState *bottom;
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BlockdevOnError on_error;
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char *backing_file_str;
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bool bs_read_only;
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bool chain_frozen;
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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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{
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assert(bytes < SIZE_MAX);
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return blk_co_preadv(blk, offset, bytes, NULL,
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BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
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}
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static void stream_abort(Job *job)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
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if (s->chain_frozen) {
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BlockJob *bjob = &s->common;
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bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->bottom);
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}
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}
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static int stream_prepare(Job *job)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
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BlockJob *bjob = &s->common;
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BlockDriverState *bs = blk_bs(bjob->blk);
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BlockDriverState *base = backing_bs(s->bottom);
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Error *local_err = NULL;
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int ret = 0;
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bdrv_unfreeze_backing_chain(bs, s->bottom);
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s->chain_frozen = false;
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if (bs->backing) {
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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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bdrv_set_backing_hd(bs, base, &local_err);
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ret = bdrv_change_backing_file(bs, base_id, base_fmt, false);
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if (local_err) {
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error_report_err(local_err);
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return -EPERM;
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}
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}
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return ret;
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}
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static void stream_clean(Job *job)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
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BlockJob *bjob = &s->common;
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BlockDriverState *bs = blk_bs(bjob->blk);
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/* Reopen the image back in read-only mode if necessary */
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if (s->bs_read_only) {
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/* Give up write permissions before making it read-only */
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blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
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bdrv_reopen_set_read_only(bs, true, NULL);
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}
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g_free(s->backing_file_str);
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}
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static int coroutine_fn stream_run(Job *job, Error **errp)
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{
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StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
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BlockBackend *blk = s->common.blk;
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BlockDriverState *bs = blk_bs(blk);
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bool enable_cor = !backing_bs(s->bottom);
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int64_t len;
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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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int64_t n = 0; /* bytes */
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if (bs == s->bottom) {
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/* Nothing to stream */
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return 0;
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}
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len = bdrv_getlength(bs);
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if (len < 0) {
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return len;
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}
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job_progress_set_remaining(&s->common.job, len);
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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 (enable_cor) {
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bdrv_enable_copy_on_read(bs);
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}
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for ( ; offset < len; offset += n) {
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bool copy;
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int ret;
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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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job_sleep_ns(&s->common.job, delay_ns);
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if (job_is_cancelled(&s->common.job)) {
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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_CHUNK, &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), s->bottom, true,
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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 = 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);
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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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/* Publish progress */
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job_progress_update(&s->common.job, n);
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if (copy) {
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delay_ns = block_job_ratelimit_get_delay(&s->common, n);
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} else {
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delay_ns = 0;
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}
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}
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if (enable_cor) {
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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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return error;
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}
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static const BlockJobDriver stream_job_driver = {
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.job_driver = {
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.instance_size = sizeof(StreamBlockJob),
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.job_type = JOB_TYPE_STREAM,
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.free = block_job_free,
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.run = stream_run,
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.prepare = stream_prepare,
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.abort = stream_abort,
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.clean = stream_clean,
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.user_resume = block_job_user_resume,
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},
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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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int creation_flags, int64_t speed,
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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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bool bs_read_only;
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int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
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BlockDriverState *bottom = bdrv_find_overlay(bs, base);
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if (bdrv_freeze_backing_chain(bs, bottom, errp) < 0) {
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return;
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}
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/* Make sure that the image is opened in read-write mode */
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bs_read_only = bdrv_is_read_only(bs);
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if (bs_read_only) {
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if (bdrv_reopen_set_read_only(bs, false, errp) != 0) {
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bs_read_only = false;
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goto fail;
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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, NULL, bs,
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basic_flags | BLK_PERM_GRAPH_MOD,
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basic_flags | BLK_PERM_WRITE,
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speed, creation_flags, 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 forbid writes
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* and resizes. Reassign the base node pointer because the backing BS of the
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* bottom node might change after the call to bdrv_reopen_set_read_only()
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* due to parallel block jobs running.
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*/
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base = backing_bs(bottom);
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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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basic_flags, &error_abort);
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}
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s->bottom = bottom;
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s->backing_file_str = g_strdup(backing_file_str);
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s->bs_read_only = bs_read_only;
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s->chain_frozen = true;
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s->on_error = on_error;
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trace_stream_start(bs, base, s);
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job_start(&s->common.job);
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return;
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fail:
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if (bs_read_only) {
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bdrv_reopen_set_read_only(bs, true, NULL);
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}
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bdrv_unfreeze_backing_chain(bs, bottom);
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}
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