/* * 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 "qemu/ratelimit.h" #include "sysemu/block-backend.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 *bottom; BlockdevOnError on_error; char *backing_file_str; bool bs_read_only; bool chain_frozen; } 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_COPY_ON_READ | BDRV_REQ_PREFETCH); } static void stream_abort(Job *job) { StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); if (s->chain_frozen) { BlockJob *bjob = &s->common; bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->bottom); } } static int stream_prepare(Job *job) { StreamBlockJob *s = container_of(job, StreamBlockJob, common.job); BlockJob *bjob = &s->common; BlockDriverState *bs = blk_bs(bjob->blk); BlockDriverState *base = backing_bs(s->bottom); Error *local_err = NULL; int ret = 0; bdrv_unfreeze_backing_chain(bs, s->bottom); s->chain_frozen = false; if (bs->backing) { const char *base_id = NULL, *base_fmt = NULL; if (base) { base_id = s->backing_file_str; if (base->drv) { base_fmt = base->drv->format_name; } } bdrv_set_backing_hd(bs, base, &local_err); ret = bdrv_change_backing_file(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; BlockDriverState *bs = blk_bs(bjob->blk); /* 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(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 *bs = blk_bs(blk); bool enable_cor = !backing_bs(s->bottom); int64_t len; int64_t offset = 0; uint64_t delay_ns = 0; int error = 0; int64_t n = 0; /* bytes */ if (bs == s->bottom) { /* Nothing to stream */ return 0; } len = bdrv_getlength(bs); if (len < 0) { return len; } job_progress_set_remaining(&s->common.job, len); /* Turn on copy-on-read for the whole block device so that guest read * requests help us make progress. Only do this when copying the entire * backing chain since the copy-on-read operation does not take base into * account. */ if (enable_cor) { bdrv_enable_copy_on_read(bs); } 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(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(backing_bs(bs), s->bottom, true, offset, n, &n); /* Finish early if end of backing file has been reached */ if (ret == 0 && n == 0) { n = len - offset; } copy = (ret == 1); } 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; } } if (enable_cor) { bdrv_disable_copy_on_read(bs); } /* 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, .abort = stream_abort, .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, int creation_flags, int64_t speed, BlockdevOnError on_error, Error **errp) { StreamBlockJob *s; BlockDriverState *iter; bool bs_read_only; int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED; BlockDriverState *bottom = bdrv_find_overlay(bs, base); if (bdrv_freeze_backing_chain(bs, bottom, errp) < 0) { return; } /* Make sure that the image is opened in read-write mode */ bs_read_only = bdrv_is_read_only(bs); if (bs_read_only) { if (bdrv_reopen_set_read_only(bs, false, errp) != 0) { bs_read_only = false; 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. */ s = block_job_create(job_id, &stream_job_driver, NULL, bs, basic_flags | BLK_PERM_GRAPH_MOD, basic_flags | BLK_PERM_WRITE, speed, creation_flags, NULL, NULL, errp); if (!s) { 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. */ base = backing_bs(bottom); for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) { block_job_add_bdrv(&s->common, "intermediate node", iter, 0, basic_flags, &error_abort); } s->bottom = bottom; s->backing_file_str = g_strdup(backing_file_str); s->bs_read_only = bs_read_only; s->chain_frozen = true; s->on_error = on_error; trace_stream_start(bs, base, s); job_start(&s->common.job); return; fail: if (bs_read_only) { bdrv_reopen_set_read_only(bs, true, NULL); } bdrv_unfreeze_backing_chain(bs, bottom); }