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-rw-r--r--block/stream.c356
1 files changed, 356 insertions, 0 deletions
diff --git a/block/stream.c b/block/stream.c
new file mode 100644
index 000000000..e45113aed
--- /dev/null
+++ b/block/stream.c
@@ -0,0 +1,356 @@
+/*
+ * 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;
+ 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;
+
+ 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(unfiltered_bs, base, &local_err);
+ ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
+ if (local_err) {
+ error_report_err(local_err);
+ return -EPERM;
+ }
+ }
+
+ return ret;
+}
+
+static void stream_clean(Job *job)
+{
+ StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
+ BlockJob *bjob = &s->common;
+
+ if (s->cor_filter_bs) {
+ bdrv_cor_filter_drop(s->cor_filter_bs);
+ s->cor_filter_bs = 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 */
+ blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
+ 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);
+ BlockBackend *blk = s->common.blk;
+ 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;
+
+ 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(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;
+
+ 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,
+ BLK_PERM_CONSISTENT_READ,
+ basic_flags | BLK_PERM_WRITE,
+ speed, creation_flags, NULL, NULL, errp);
+ if (!s) {
+ goto fail;
+ }
+
+ /*
+ * 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);
+ }
+}