Commit 6585493369
added code to freeze
the backing chain from 'top' to 'base' for the duration of the
block-stream job.
The problem is that the freezing happens too late in stream_start():
during the bdrv_reopen_set_read_only() call earlier in that function
another job can jump in and remove the base image. If that happens we
have an invalid chain and QEMU crashes.
This patch puts the bdrv_freeze_backing_chain() call at the beginning
of the function.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
293 lines
8.5 KiB
C
293 lines
8.5 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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typedef struct StreamBlockJob {
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BlockJob common;
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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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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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void *buf)
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{
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QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
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assert(bytes < SIZE_MAX);
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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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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->base);
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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 = s->base;
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Error *local_err = NULL;
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int ret = 0;
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bdrv_unfreeze_backing_chain(bs, base);
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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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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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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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BlockDriverState *base = s->base;
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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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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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len = bdrv_getlength(bs);
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if (len < 0) {
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ret = len;
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goto out;
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}
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job_progress_set_remaining(&s->common.job, len);
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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 < 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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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_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 = 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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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 (!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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return ret;
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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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.drain = block_job_drain,
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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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if (bdrv_freeze_backing_chain(bs, base, 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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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, 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 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_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, base);
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}
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