/* * Image mirroring * * Copyright Red Hat, Inc. 2012 * * Authors: * Paolo Bonzini * * 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 "trace.h" #include "block/blockjob.h" #include "block/block_int.h" #include "qemu/ratelimit.h" #include "qemu/bitmap.h" #define SLICE_TIME 100000000ULL /* ns */ #define MAX_IN_FLIGHT 16 /* The mirroring buffer is a list of granularity-sized chunks. * Free chunks are organized in a list. */ typedef struct MirrorBuffer { QSIMPLEQ_ENTRY(MirrorBuffer) next; } MirrorBuffer; typedef struct MirrorBlockJob { BlockJob common; RateLimit limit; BlockDriverState *target; BlockDriverState *base; bool is_none_mode; BlockdevOnError on_source_error, on_target_error; bool synced; bool should_complete; int64_t sector_num; int64_t granularity; size_t buf_size; unsigned long *cow_bitmap; BdrvDirtyBitmap *dirty_bitmap; HBitmapIter hbi; uint8_t *buf; QSIMPLEQ_HEAD(, MirrorBuffer) buf_free; int buf_free_count; unsigned long *in_flight_bitmap; int in_flight; int ret; } MirrorBlockJob; typedef struct MirrorOp { MirrorBlockJob *s; QEMUIOVector qiov; int64_t sector_num; int nb_sectors; } MirrorOp; static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read, int error) { s->synced = false; if (read) { return block_job_error_action(&s->common, s->common.bs, s->on_source_error, true, error); } else { return block_job_error_action(&s->common, s->target, s->on_target_error, false, error); } } static void mirror_iteration_done(MirrorOp *op, int ret) { MirrorBlockJob *s = op->s; struct iovec *iov; int64_t chunk_num; int i, nb_chunks, sectors_per_chunk; trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret); s->in_flight--; iov = op->qiov.iov; for (i = 0; i < op->qiov.niov; i++) { MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base; QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next); s->buf_free_count++; } sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; chunk_num = op->sector_num / sectors_per_chunk; nb_chunks = op->nb_sectors / sectors_per_chunk; bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks); if (s->cow_bitmap && ret >= 0) { bitmap_set(s->cow_bitmap, chunk_num, nb_chunks); } qemu_iovec_destroy(&op->qiov); g_slice_free(MirrorOp, op); qemu_coroutine_enter(s->common.co, NULL); } static void mirror_write_complete(void *opaque, int ret) { MirrorOp *op = opaque; MirrorBlockJob *s = op->s; if (ret < 0) { BlockDriverState *source = s->common.bs; BlockErrorAction action; bdrv_set_dirty(source, op->sector_num, op->nb_sectors); action = mirror_error_action(s, false, -ret); if (action == BDRV_ACTION_REPORT && s->ret >= 0) { s->ret = ret; } } mirror_iteration_done(op, ret); } static void mirror_read_complete(void *opaque, int ret) { MirrorOp *op = opaque; MirrorBlockJob *s = op->s; if (ret < 0) { BlockDriverState *source = s->common.bs; BlockErrorAction action; bdrv_set_dirty(source, op->sector_num, op->nb_sectors); action = mirror_error_action(s, true, -ret); if (action == BDRV_ACTION_REPORT && s->ret >= 0) { s->ret = ret; } mirror_iteration_done(op, ret); return; } bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors, mirror_write_complete, op); } static void coroutine_fn mirror_iteration(MirrorBlockJob *s) { BlockDriverState *source = s->common.bs; int nb_sectors, sectors_per_chunk, nb_chunks; int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector; MirrorOp *op; s->sector_num = hbitmap_iter_next(&s->hbi); if (s->sector_num < 0) { bdrv_dirty_iter_init(source, s->dirty_bitmap, &s->hbi); s->sector_num = hbitmap_iter_next(&s->hbi); trace_mirror_restart_iter(s, bdrv_get_dirty_count(source, s->dirty_bitmap)); assert(s->sector_num >= 0); } hbitmap_next_sector = s->sector_num; sector_num = s->sector_num; sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; end = s->common.len >> BDRV_SECTOR_BITS; /* Extend the QEMUIOVector to include all adjacent blocks that will * be copied in this operation. * * We have to do this if we have no backing file yet in the destination, * and the cluster size is very large. Then we need to do COW ourselves. * The first time a cluster is copied, copy it entirely. Note that, * because both the granularity and the cluster size are powers of two, * the number of sectors to copy cannot exceed one cluster. * * We also want to extend the QEMUIOVector to include more adjacent * dirty blocks if possible, to limit the number of I/O operations and * run efficiently even with a small granularity. */ nb_chunks = 0; nb_sectors = 0; next_sector = sector_num; next_chunk = sector_num / sectors_per_chunk; /* Wait for I/O to this cluster (from a previous iteration) to be done. */ while (test_bit(next_chunk, s->in_flight_bitmap)) { trace_mirror_yield_in_flight(s, sector_num, s->in_flight); qemu_coroutine_yield(); } do { int added_sectors, added_chunks; if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) || test_bit(next_chunk, s->in_flight_bitmap)) { assert(nb_sectors > 0); break; } added_sectors = sectors_per_chunk; if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) { bdrv_round_to_clusters(s->target, next_sector, added_sectors, &next_sector, &added_sectors); /* On the first iteration, the rounding may make us copy * sectors before the first dirty one. */ if (next_sector < sector_num) { assert(nb_sectors == 0); sector_num = next_sector; next_chunk = next_sector / sectors_per_chunk; } } added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors)); added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk; /* When doing COW, it may happen that there is not enough space for * a full cluster. Wait if that is the case. */ while (nb_chunks == 0 && s->buf_free_count < added_chunks) { trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight); qemu_coroutine_yield(); } if (s->buf_free_count < nb_chunks + added_chunks) { trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight); break; } /* We have enough free space to copy these sectors. */ bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks); nb_sectors += added_sectors; nb_chunks += added_chunks; next_sector += added_sectors; next_chunk += added_chunks; } while (next_sector < end); /* Allocate a MirrorOp that is used as an AIO callback. */ op = g_slice_new(MirrorOp); op->s = s; op->sector_num = sector_num; op->nb_sectors = nb_sectors; /* Now make a QEMUIOVector taking enough granularity-sized chunks * from s->buf_free. */ qemu_iovec_init(&op->qiov, nb_chunks); next_sector = sector_num; while (nb_chunks-- > 0) { MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free); QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next); s->buf_free_count--; qemu_iovec_add(&op->qiov, buf, s->granularity); /* Advance the HBitmapIter in parallel, so that we do not examine * the same sector twice. */ if (next_sector > hbitmap_next_sector && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) { hbitmap_next_sector = hbitmap_iter_next(&s->hbi); } next_sector += sectors_per_chunk; } bdrv_reset_dirty(source, sector_num, nb_sectors); /* Copy the dirty cluster. */ s->in_flight++; trace_mirror_one_iteration(s, sector_num, nb_sectors); bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors, mirror_read_complete, op); } static void mirror_free_init(MirrorBlockJob *s) { int granularity = s->granularity; size_t buf_size = s->buf_size; uint8_t *buf = s->buf; assert(s->buf_free_count == 0); QSIMPLEQ_INIT(&s->buf_free); while (buf_size != 0) { MirrorBuffer *cur = (MirrorBuffer *)buf; QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next); s->buf_free_count++; buf_size -= granularity; buf += granularity; } } static void mirror_drain(MirrorBlockJob *s) { while (s->in_flight > 0) { qemu_coroutine_yield(); } } static void coroutine_fn mirror_run(void *opaque) { MirrorBlockJob *s = opaque; BlockDriverState *bs = s->common.bs; int64_t sector_num, end, sectors_per_chunk, length; uint64_t last_pause_ns; BlockDriverInfo bdi; char backing_filename[1024]; int ret = 0; int n; if (block_job_is_cancelled(&s->common)) { goto immediate_exit; } s->common.len = bdrv_getlength(bs); if (s->common.len <= 0) { block_job_completed(&s->common, s->common.len); return; } length = (bdrv_getlength(bs) + s->granularity - 1) / s->granularity; s->in_flight_bitmap = bitmap_new(length); /* If we have no backing file yet in the destination, we cannot let * the destination do COW. Instead, we copy sectors around the * dirty data if needed. We need a bitmap to do that. */ bdrv_get_backing_filename(s->target, backing_filename, sizeof(backing_filename)); if (backing_filename[0] && !s->target->backing_hd) { bdrv_get_info(s->target, &bdi); if (s->granularity < bdi.cluster_size) { s->buf_size = MAX(s->buf_size, bdi.cluster_size); s->cow_bitmap = bitmap_new(length); } } end = s->common.len >> BDRV_SECTOR_BITS; s->buf = qemu_blockalign(bs, s->buf_size); sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS; mirror_free_init(s); if (!s->is_none_mode) { /* First part, loop on the sectors and initialize the dirty bitmap. */ BlockDriverState *base = s->base; for (sector_num = 0; sector_num < end; ) { int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1; ret = bdrv_is_allocated_above(bs, base, sector_num, next - sector_num, &n); if (ret < 0) { goto immediate_exit; } assert(n > 0); if (ret == 1) { bdrv_set_dirty(bs, sector_num, n); sector_num = next; } else { sector_num += n; } } } bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi); last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); for (;;) { uint64_t delay_ns; int64_t cnt; bool should_complete; if (s->ret < 0) { ret = s->ret; goto immediate_exit; } cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap); /* Note that even when no rate limit is applied we need to yield * periodically with no pending I/O so that qemu_aio_flush() returns. * We do so every SLICE_TIME nanoseconds, or when there is an error, * or when the source is clean, whichever comes first. */ if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME && s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) { if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 || (cnt == 0 && s->in_flight > 0)) { trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt); qemu_coroutine_yield(); continue; } else if (cnt != 0) { mirror_iteration(s); continue; } } should_complete = false; if (s->in_flight == 0 && cnt == 0) { trace_mirror_before_flush(s); ret = bdrv_flush(s->target); if (ret < 0) { if (mirror_error_action(s, false, -ret) == BDRV_ACTION_REPORT) { goto immediate_exit; } } else { /* We're out of the streaming phase. From now on, if the job * is cancelled we will actually complete all pending I/O and * report completion. This way, block-job-cancel will leave * the target in a consistent state. */ s->common.offset = end * BDRV_SECTOR_SIZE; if (!s->synced) { block_job_ready(&s->common); s->synced = true; } should_complete = s->should_complete || block_job_is_cancelled(&s->common); cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap); } } if (cnt == 0 && should_complete) { /* The dirty bitmap is not updated while operations are pending. * If we're about to exit, wait for pending operations before * calling bdrv_get_dirty_count(bs), or we may exit while the * source has dirty data to copy! * * Note that I/O can be submitted by the guest while * mirror_populate runs. */ trace_mirror_before_drain(s, cnt); bdrv_drain_all(); cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap); } ret = 0; trace_mirror_before_sleep(s, cnt, s->synced); if (!s->synced) { /* Publish progress */ s->common.offset = (end - cnt) * BDRV_SECTOR_SIZE; if (s->common.speed) { delay_ns = ratelimit_calculate_delay(&s->limit, sectors_per_chunk); } else { delay_ns = 0; } block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns); if (block_job_is_cancelled(&s->common)) { break; } } else if (!should_complete) { delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0); block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns); } else if (cnt == 0) { /* The two disks are in sync. Exit and report successful * completion. */ assert(QLIST_EMPTY(&bs->tracked_requests)); s->common.cancelled = false; break; } last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME); } immediate_exit: if (s->in_flight > 0) { /* We get here only if something went wrong. Either the job failed, * or it was cancelled prematurely so that we do not guarantee that * the target is a copy of the source. */ assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common))); mirror_drain(s); } assert(s->in_flight == 0); qemu_vfree(s->buf); g_free(s->cow_bitmap); g_free(s->in_flight_bitmap); bdrv_release_dirty_bitmap(bs, s->dirty_bitmap); bdrv_iostatus_disable(s->target); if (s->should_complete && ret == 0) { if (bdrv_get_flags(s->target) != bdrv_get_flags(s->common.bs)) { bdrv_reopen(s->target, bdrv_get_flags(s->common.bs), NULL); } bdrv_swap(s->target, s->common.bs); if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) { /* drop the bs loop chain formed by the swap: break the loop then * trigger the unref from the top one */ BlockDriverState *p = s->base->backing_hd; s->base->backing_hd = NULL; bdrv_unref(p); } } bdrv_unref(s->target); block_job_completed(&s->common, ret); } static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp) { MirrorBlockJob *s = container_of(job, MirrorBlockJob, common); if (speed < 0) { error_set(errp, QERR_INVALID_PARAMETER, "speed"); return; } ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); } static void mirror_iostatus_reset(BlockJob *job) { MirrorBlockJob *s = container_of(job, MirrorBlockJob, common); bdrv_iostatus_reset(s->target); } static void mirror_complete(BlockJob *job, Error **errp) { MirrorBlockJob *s = container_of(job, MirrorBlockJob, common); Error *local_err = NULL; int ret; ret = bdrv_open_backing_file(s->target, NULL, &local_err); if (ret < 0) { error_propagate(errp, local_err); return; } if (!s->synced) { error_set(errp, QERR_BLOCK_JOB_NOT_READY, job->bs->device_name); return; } s->should_complete = true; block_job_resume(job); } static const BlockJobDriver mirror_job_driver = { .instance_size = sizeof(MirrorBlockJob), .job_type = BLOCK_JOB_TYPE_MIRROR, .set_speed = mirror_set_speed, .iostatus_reset= mirror_iostatus_reset, .complete = mirror_complete, }; static const BlockJobDriver commit_active_job_driver = { .instance_size = sizeof(MirrorBlockJob), .job_type = BLOCK_JOB_TYPE_COMMIT, .set_speed = mirror_set_speed, .iostatus_reset = mirror_iostatus_reset, .complete = mirror_complete, }; static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target, int64_t speed, int64_t granularity, int64_t buf_size, BlockdevOnError on_source_error, BlockdevOnError on_target_error, BlockDriverCompletionFunc *cb, void *opaque, Error **errp, const BlockJobDriver *driver, bool is_none_mode, BlockDriverState *base) { MirrorBlockJob *s; if (granularity == 0) { /* Choose the default granularity based on the target file's cluster * size, clamped between 4k and 64k. */ BlockDriverInfo bdi; if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) { granularity = MAX(4096, bdi.cluster_size); granularity = MIN(65536, granularity); } else { granularity = 65536; } } assert ((granularity & (granularity - 1)) == 0); if ((on_source_error == BLOCKDEV_ON_ERROR_STOP || on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) && !bdrv_iostatus_is_enabled(bs)) { error_set(errp, QERR_INVALID_PARAMETER, "on-source-error"); return; } s = block_job_create(driver, bs, speed, cb, opaque, errp); if (!s) { return; } s->on_source_error = on_source_error; s->on_target_error = on_target_error; s->target = target; s->is_none_mode = is_none_mode; s->base = base; s->granularity = granularity; s->buf_size = MAX(buf_size, granularity); s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity); bdrv_set_enable_write_cache(s->target, true); bdrv_set_on_error(s->target, on_target_error, on_target_error); bdrv_iostatus_enable(s->target); s->common.co = qemu_coroutine_create(mirror_run); trace_mirror_start(bs, s, s->common.co, opaque); qemu_coroutine_enter(s->common.co, s); } void mirror_start(BlockDriverState *bs, BlockDriverState *target, int64_t speed, int64_t granularity, int64_t buf_size, MirrorSyncMode mode, BlockdevOnError on_source_error, BlockdevOnError on_target_error, BlockDriverCompletionFunc *cb, void *opaque, Error **errp) { bool is_none_mode; BlockDriverState *base; is_none_mode = mode == MIRROR_SYNC_MODE_NONE; base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL; mirror_start_job(bs, target, speed, granularity, buf_size, on_source_error, on_target_error, cb, opaque, errp, &mirror_job_driver, is_none_mode, base); } void commit_active_start(BlockDriverState *bs, BlockDriverState *base, int64_t speed, BlockdevOnError on_error, BlockDriverCompletionFunc *cb, void *opaque, Error **errp) { int64_t length, base_length; int orig_base_flags; int ret; Error *local_err = NULL; orig_base_flags = bdrv_get_flags(base); if (bdrv_reopen(base, bs->open_flags, errp)) { return; } length = bdrv_getlength(bs); if (length < 0) { error_setg_errno(errp, -length, "Unable to determine length of %s", bs->filename); goto error_restore_flags; } base_length = bdrv_getlength(base); if (base_length < 0) { error_setg_errno(errp, -base_length, "Unable to determine length of %s", base->filename); goto error_restore_flags; } if (length > base_length) { ret = bdrv_truncate(base, length); if (ret < 0) { error_setg_errno(errp, -ret, "Top image %s is larger than base image %s, and " "resize of base image failed", bs->filename, base->filename); goto error_restore_flags; } } bdrv_ref(base); mirror_start_job(bs, base, speed, 0, 0, on_error, on_error, cb, opaque, &local_err, &commit_active_job_driver, false, base); if (error_is_set(&local_err)) { error_propagate(errp, local_err); goto error_restore_flags; } return; error_restore_flags: /* ignore error and errp for bdrv_reopen, because we want to propagate * the original error */ bdrv_reopen(base, orig_base_flags, NULL); return; }