/* * 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 { /* * Size of data buffer for populating the image file. This should be large * enough to process multiple clusters in a single call, so that populating * contiguous regions of the image is efficient. */ STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */ }; #define SLICE_TIME 100000000ULL /* ns */ typedef struct StreamBlockJob { BlockJob common; RateLimit limit; BlockDriverState *base; BlockdevOnError on_error; char *backing_file_str; int bs_flags; } StreamBlockJob; static int coroutine_fn stream_populate(BlockBackend *blk, int64_t offset, uint64_t bytes, void *buf) { struct iovec iov = { .iov_base = buf, .iov_len = bytes, }; QEMUIOVector qiov; assert(bytes < SIZE_MAX); qemu_iovec_init_external(&qiov, &iov, 1); /* Copy-on-read the unallocated clusters */ return blk_co_preadv(blk, offset, qiov.size, &qiov, BDRV_REQ_COPY_ON_READ); } typedef struct { int ret; } StreamCompleteData; static void stream_complete(BlockJob *job, void *opaque) { StreamBlockJob *s = container_of(job, StreamBlockJob, common); StreamCompleteData *data = opaque; BlockDriverState *bs = blk_bs(job->blk); BlockDriverState *base = s->base; Error *local_err = NULL; if (!block_job_is_cancelled(&s->common) && bs->backing && data->ret == 0) { 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; } } data->ret = bdrv_change_backing_file(bs, base_id, base_fmt); bdrv_set_backing_hd(bs, base, &local_err); if (local_err) { error_report_err(local_err); data->ret = -EPERM; goto out; } } out: /* Reopen the image back in read-only mode if necessary */ if (s->bs_flags != bdrv_get_flags(bs)) { /* Give up write permissions before making it read-only */ blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort); bdrv_reopen(bs, s->bs_flags, NULL); } g_free(s->backing_file_str); block_job_completed(&s->common, data->ret); g_free(data); } static void coroutine_fn stream_run(void *opaque) { StreamBlockJob *s = opaque; StreamCompleteData *data; BlockBackend *blk = s->common.blk; BlockDriverState *bs = blk_bs(blk); BlockDriverState *base = s->base; int64_t offset = 0; uint64_t delay_ns = 0; int error = 0; int ret = 0; int64_t n = 0; /* bytes */ void *buf; if (!bs->backing) { goto out; } s->common.len = bdrv_getlength(bs); if (s->common.len < 0) { ret = s->common.len; goto out; } buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE); /* 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 (!base) { bdrv_enable_copy_on_read(bs); } for ( ; offset < s->common.len; offset += n) { bool copy; /* 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. */ block_job_sleep_ns(&s->common, delay_ns); if (block_job_is_cancelled(&s->common)) { break; } copy = false; ret = bdrv_is_allocated(bs, offset, STREAM_BUFFER_SIZE, &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), base, offset, n, &n); /* Finish early if end of backing file has been reached */ if (ret == 0 && n == 0) { n = s->common.len - offset; } copy = (ret == 1); } trace_stream_one_iteration(s, offset, n, ret); if (copy) { ret = stream_populate(blk, offset, n, buf); } 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; } } ret = 0; /* Publish progress */ s->common.offset += n; if (copy && s->common.speed) { delay_ns = ratelimit_calculate_delay(&s->limit, n); } } if (!base) { bdrv_disable_copy_on_read(bs); } /* Do not remove the backing file if an error was there but ignored. */ ret = error; qemu_vfree(buf); out: /* Modify backing chain and close BDSes in main loop */ data = g_malloc(sizeof(*data)); data->ret = ret; block_job_defer_to_main_loop(&s->common, stream_complete, data); } static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp) { StreamBlockJob *s = container_of(job, StreamBlockJob, common); if (speed < 0) { error_setg(errp, QERR_INVALID_PARAMETER, "speed"); return; } ratelimit_set_speed(&s->limit, speed, SLICE_TIME); } static const BlockJobDriver stream_job_driver = { .instance_size = sizeof(StreamBlockJob), .job_type = BLOCK_JOB_TYPE_STREAM, .set_speed = stream_set_speed, .start = stream_run, }; void stream_start(const char *job_id, BlockDriverState *bs, BlockDriverState *base, const char *backing_file_str, int64_t speed, BlockdevOnError on_error, Error **errp) { StreamBlockJob *s; BlockDriverState *iter; int orig_bs_flags; /* Make sure that the image is opened in read-write mode */ orig_bs_flags = bdrv_get_flags(bs); if (!(orig_bs_flags & BDRV_O_RDWR)) { if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) { return; } } /* 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, bs, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_WRITE, speed, BLOCK_JOB_DEFAULT, 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 block writes * and resizes. */ for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) { block_job_add_bdrv(&s->common, "intermediate node", iter, 0, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED, &error_abort); } s->base = base; s->backing_file_str = g_strdup(backing_file_str); s->bs_flags = orig_bs_flags; s->on_error = on_error; trace_stream_start(bs, base, s); block_job_start(&s->common); return; fail: if (orig_bs_flags != bdrv_get_flags(bs)) { bdrv_reopen(bs, orig_bs_flags, NULL); } }