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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 "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 "qapi/qmp/qdict.h"
#include "qemu/ratelimit.h"
#include "sysemu/block-backend.h"
#include "block/copy-on-read.h"
enum {
/*
* Maximum chunk size to feed to copy-on-read. This should be
* large enough to process multiple clusters in a single call, so
* that populating contiguous regions of the image is efficient.
*/
STREAM_CHUNK = 512 * 1024, /* in bytes */
};
typedef struct StreamBlockJob {
BlockJob common;
BlockBackend *blk;
BlockDriverState *base_overlay; /* COW overlay (stream from this) */
BlockDriverState *above_base; /* Node directly above the base */
BlockDriverState *cor_filter_bs;
BlockDriverState *target_bs;
BlockdevOnError on_error;
char *backing_file_str;
bool bs_read_only;
} StreamBlockJob;
static int coroutine_fn stream_populate(BlockBackend *blk,
int64_t offset, uint64_t bytes)
{
assert(bytes < SIZE_MAX);
return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
}
static int stream_prepare(Job *job)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
BlockDriverState *base;
BlockDriverState *unfiltered_base;
Error *local_err = NULL;
int ret = 0;
/* We should drop filter at this point, as filter hold the backing chain */
bdrv_cor_filter_drop(s->cor_filter_bs);
s->cor_filter_bs = NULL;
/*
* bdrv_set_backing_hd() requires that unfiltered_bs is drained. Drain
* already here and use bdrv_set_backing_hd_drained() instead because
* the polling during drained_begin() might change the graph, and if we do
* this only later, we may end up working with the wrong base node (or it
* might even have gone away by the time we want to use it).
*/
bdrv_drained_begin(unfiltered_bs);
base = bdrv_filter_or_cow_bs(s->above_base);
unfiltered_base = bdrv_skip_filters(base);
if (bdrv_cow_child(unfiltered_bs)) {
const char *base_id = NULL, *base_fmt = NULL;
if (unfiltered_base) {
base_id = s->backing_file_str ?: unfiltered_base->filename;
if (unfiltered_base->drv) {
base_fmt = unfiltered_base->drv->format_name;
}
}
bdrv_set_backing_hd_drained(unfiltered_bs, base, &local_err);
/*
* This call will do I/O, so the graph can change again from here on.
* We have already completed the graph change, so we are not in danger
* of operating on the wrong node any more if this happens.
*/
ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
if (local_err) {
error_report_err(local_err);
ret = -EPERM;
goto out;
}
}
out:
bdrv_drained_end(unfiltered_bs);
return ret;
}
static void stream_clean(Job *job)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
if (s->cor_filter_bs) {
bdrv_cor_filter_drop(s->cor_filter_bs);
s->cor_filter_bs = NULL;
}
blk_unref(s->blk);
s->blk = NULL;
/* Reopen the image back in read-only mode if necessary */
if (s->bs_read_only) {
/* Give up write permissions before making it read-only */
bdrv_reopen_set_read_only(s->target_bs, true, NULL);
}
g_free(s->backing_file_str);
}
static int coroutine_fn stream_run(Job *job, Error **errp)
{
StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
int64_t len;
int64_t offset = 0;
uint64_t delay_ns = 0;
int error = 0;
int64_t n = 0; /* bytes */
if (unfiltered_bs == s->base_overlay) {
/* Nothing to stream */
return 0;
}
len = bdrv_getlength(s->target_bs);
if (len < 0) {
return len;
}
job_progress_set_remaining(&s->common.job, len);
for ( ; offset < len; offset += n) {
bool copy;
int ret;
/* 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.
*/
job_sleep_ns(&s->common.job, delay_ns);
if (job_is_cancelled(&s->common.job)) {
break;
}
copy = false;
WITH_GRAPH_RDLOCK_GUARD() {
ret = bdrv_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &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(bdrv_cow_bs(unfiltered_bs),
s->base_overlay, true,
offset, n, &n);
/* Finish early if end of backing file has been reached */
if (ret == 0 && n == 0) {
n = len - offset;
}
copy = (ret > 0);
}
}
trace_stream_one_iteration(s, offset, n, ret);
if (copy) {
ret = stream_populate(s->blk, offset, n);
}
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;
}
}
/* Publish progress */
job_progress_update(&s->common.job, n);
if (copy) {
delay_ns = block_job_ratelimit_get_delay(&s->common, n);
} else {
delay_ns = 0;
}
}
/* Do not remove the backing file if an error was there but ignored. */
return error;
}
static const BlockJobDriver stream_job_driver = {
.job_driver = {
.instance_size = sizeof(StreamBlockJob),
.job_type = JOB_TYPE_STREAM,
.free = block_job_free,
.run = stream_run,
.prepare = stream_prepare,
.clean = stream_clean,
.user_resume = block_job_user_resume,
},
};
void stream_start(const char *job_id, BlockDriverState *bs,
BlockDriverState *base, const char *backing_file_str,
BlockDriverState *bottom,
int creation_flags, int64_t speed,
BlockdevOnError on_error,
const char *filter_node_name,
Error **errp)
{
StreamBlockJob *s = NULL;
BlockDriverState *iter;
bool bs_read_only;
int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
BlockDriverState *base_overlay;
BlockDriverState *cor_filter_bs = NULL;
BlockDriverState *above_base;
QDict *opts;
int ret;
GLOBAL_STATE_CODE();
assert(!(base && bottom));
assert(!(backing_file_str && bottom));
if (bottom) {
/*
* New simple interface. The code is written in terms of old interface
* with @base parameter (still, it doesn't freeze link to base, so in
* this mean old code is correct for new interface). So, for now, just
* emulate base_overlay and above_base. Still, when old interface
* finally removed, we should refactor code to use only "bottom", but
* not "*base*" things.
*/
assert(!bottom->drv->is_filter);
base_overlay = above_base = bottom;
} else {
base_overlay = bdrv_find_overlay(bs, base);
if (!base_overlay) {
error_setg(errp, "'%s' is not in the backing chain of '%s'",
base->node_name, bs->node_name);
return;
}
/*
* Find the node directly above @base. @base_overlay is a COW overlay,
* so it must have a bdrv_cow_child(), but it is the immediate overlay
* of @base, so between the two there can only be filters.
*/
above_base = base_overlay;
if (bdrv_cow_bs(above_base) != base) {
above_base = bdrv_cow_bs(above_base);
while (bdrv_filter_bs(above_base) != base) {
above_base = bdrv_filter_bs(above_base);
}
}
}
/* Make sure that the image is opened in read-write mode */
bs_read_only = bdrv_is_read_only(bs);
if (bs_read_only) {
int ret;
/* Hold the chain during reopen */
if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
return;
}
ret = bdrv_reopen_set_read_only(bs, false, errp);
/* failure, or cor-filter will hold the chain */
bdrv_unfreeze_backing_chain(bs, above_base);
if (ret < 0) {
return;
}
}
opts = qdict_new();
qdict_put_str(opts, "driver", "copy-on-read");
qdict_put_str(opts, "file", bdrv_get_node_name(bs));
/* Pass the base_overlay node name as 'bottom' to COR driver */
qdict_put_str(opts, "bottom", base_overlay->node_name);
if (filter_node_name) {
qdict_put_str(opts, "node-name", filter_node_name);
}
cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
if (!cor_filter_bs) {
goto fail;
}
if (!filter_node_name) {
cor_filter_bs->implicit = true;
}
s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
0, BLK_PERM_ALL,
speed, creation_flags, NULL, NULL, errp);
if (!s) {
goto fail;
}
s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ,
basic_flags | BLK_PERM_WRITE, errp);
if (!s->blk) {
goto fail;
}
/*
* Disable request queuing in the BlockBackend to avoid deadlocks on drain:
* The job reports that it's busy until it reaches a pause point.
*/
blk_set_disable_request_queuing(s->blk, true);
blk_set_allow_aio_context_change(s->blk, true);
/*
* 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.
*/
if (block_job_add_bdrv(&s->common, "active node", bs, 0,
basic_flags | BLK_PERM_WRITE, errp)) {
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 forbid writes
* and resizes. Reassign the base node pointer because the backing BS of the
* bottom node might change after the call to bdrv_reopen_set_read_only()
* due to parallel block jobs running.
* above_base node might change after the call to
* bdrv_reopen_set_read_only() due to parallel block jobs running.
*/
base = bdrv_filter_or_cow_bs(above_base);
for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
iter = bdrv_filter_or_cow_bs(iter))
{
ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
basic_flags, errp);
if (ret < 0) {
goto fail;
}
}
s->base_overlay = base_overlay;
s->above_base = above_base;
s->backing_file_str = g_strdup(backing_file_str);
s->cor_filter_bs = cor_filter_bs;
s->target_bs = bs;
s->bs_read_only = bs_read_only;
s->on_error = on_error;
trace_stream_start(bs, base, s);
job_start(&s->common.job);
return;
fail:
if (s) {
job_early_fail(&s->common.job);
}
if (cor_filter_bs) {
bdrv_cor_filter_drop(cor_filter_bs);
}
if (bs_read_only) {
bdrv_reopen_set_read_only(bs, true, NULL);
}
}
|