diff options
Diffstat (limited to 'block/stream.c')
| -rw-r--r-- | block/stream.c | 356 |
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); + } +} |