/* * QEMU backup * * Copyright (C) 2013 Proxmox Server Solutions * * Authors: * Dietmar Maurer (dietmar@proxmox.com) * * This work is licensed under the terms of the GNU GPL, version 2 or later. * See the COPYING file in the top-level directory. * */ #include "qemu/osdep.h" #include "trace.h" #include "block/block.h" #include "block/block_int.h" #include "block/blockjob.h" #include "qapi/error.h" #include "qapi/qmp/qerror.h" #include "qemu/ratelimit.h" #include "qemu/cutils.h" #include "sysemu/block-backend.h" #include "qemu/bitmap.h" #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16) #define SLICE_TIME 100000000ULL /* ns */ typedef struct CowRequest { int64_t start; int64_t end; QLIST_ENTRY(CowRequest) list; CoQueue wait_queue; /* coroutines blocked on this request */ } CowRequest; typedef struct BackupBlockJob { BlockJob common; BlockBackend *target; /* bitmap for sync=incremental */ BdrvDirtyBitmap *sync_bitmap; MirrorSyncMode sync_mode; RateLimit limit; BlockdevOnError on_source_error; BlockdevOnError on_target_error; CoRwlock flush_rwlock; uint64_t sectors_read; unsigned long *done_bitmap; int64_t cluster_size; NotifierWithReturn before_write; QLIST_HEAD(, CowRequest) inflight_reqs; } BackupBlockJob; /* Size of a cluster in sectors, instead of bytes. */ static inline int64_t cluster_size_sectors(BackupBlockJob *job) { return job->cluster_size / BDRV_SECTOR_SIZE; } /* See if in-flight requests overlap and wait for them to complete */ static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job, int64_t start, int64_t end) { CowRequest *req; bool retry; do { retry = false; QLIST_FOREACH(req, &job->inflight_reqs, list) { if (end > req->start && start < req->end) { qemu_co_queue_wait(&req->wait_queue); retry = true; break; } } } while (retry); } /* Keep track of an in-flight request */ static void cow_request_begin(CowRequest *req, BackupBlockJob *job, int64_t start, int64_t end) { req->start = start; req->end = end; qemu_co_queue_init(&req->wait_queue); QLIST_INSERT_HEAD(&job->inflight_reqs, req, list); } /* Forget about a completed request */ static void cow_request_end(CowRequest *req) { QLIST_REMOVE(req, list); qemu_co_queue_restart_all(&req->wait_queue); } static int coroutine_fn backup_do_cow(BackupBlockJob *job, int64_t sector_num, int nb_sectors, bool *error_is_read, bool is_write_notifier) { BlockBackend *blk = job->common.blk; CowRequest cow_request; struct iovec iov; QEMUIOVector bounce_qiov; void *bounce_buffer = NULL; int ret = 0; int64_t sectors_per_cluster = cluster_size_sectors(job); int64_t start, end; int n; qemu_co_rwlock_rdlock(&job->flush_rwlock); start = sector_num / sectors_per_cluster; end = DIV_ROUND_UP(sector_num + nb_sectors, sectors_per_cluster); trace_backup_do_cow_enter(job, start, sector_num, nb_sectors); wait_for_overlapping_requests(job, start, end); cow_request_begin(&cow_request, job, start, end); for (; start < end; start++) { if (test_bit(start, job->done_bitmap)) { trace_backup_do_cow_skip(job, start); continue; /* already copied */ } trace_backup_do_cow_process(job, start); n = MIN(sectors_per_cluster, job->common.len / BDRV_SECTOR_SIZE - start * sectors_per_cluster); if (!bounce_buffer) { bounce_buffer = blk_blockalign(blk, job->cluster_size); } iov.iov_base = bounce_buffer; iov.iov_len = n * BDRV_SECTOR_SIZE; qemu_iovec_init_external(&bounce_qiov, &iov, 1); ret = blk_co_preadv(blk, start * job->cluster_size, bounce_qiov.size, &bounce_qiov, is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0); if (ret < 0) { trace_backup_do_cow_read_fail(job, start, ret); if (error_is_read) { *error_is_read = true; } goto out; } if (buffer_is_zero(iov.iov_base, iov.iov_len)) { ret = blk_co_pwrite_zeroes(job->target, start * job->cluster_size, bounce_qiov.size, BDRV_REQ_MAY_UNMAP); } else { ret = blk_co_pwritev(job->target, start * job->cluster_size, bounce_qiov.size, &bounce_qiov, 0); } if (ret < 0) { trace_backup_do_cow_write_fail(job, start, ret); if (error_is_read) { *error_is_read = false; } goto out; } set_bit(start, job->done_bitmap); /* Publish progress, guest I/O counts as progress too. Note that the * offset field is an opaque progress value, it is not a disk offset. */ job->sectors_read += n; job->common.offset += n * BDRV_SECTOR_SIZE; } out: if (bounce_buffer) { qemu_vfree(bounce_buffer); } cow_request_end(&cow_request); trace_backup_do_cow_return(job, sector_num, nb_sectors, ret); qemu_co_rwlock_unlock(&job->flush_rwlock); return ret; } static int coroutine_fn backup_before_write_notify( NotifierWithReturn *notifier, void *opaque) { BackupBlockJob *job = container_of(notifier, BackupBlockJob, before_write); BdrvTrackedRequest *req = opaque; int64_t sector_num = req->offset >> BDRV_SECTOR_BITS; int nb_sectors = req->bytes >> BDRV_SECTOR_BITS; assert(req->bs == blk_bs(job->common.blk)); assert((req->offset & (BDRV_SECTOR_SIZE - 1)) == 0); assert((req->bytes & (BDRV_SECTOR_SIZE - 1)) == 0); return backup_do_cow(job, sector_num, nb_sectors, NULL, true); } static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); if (speed < 0) { error_setg(errp, QERR_INVALID_PARAMETER, "speed"); return; } ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); } static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) { BdrvDirtyBitmap *bm; BlockDriverState *bs = blk_bs(job->common.blk); if (ret < 0 || block_job_is_cancelled(&job->common)) { /* Merge the successor back into the parent, delete nothing. */ bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL); assert(bm); } else { /* Everything is fine, delete this bitmap and install the backup. */ bm = bdrv_dirty_bitmap_abdicate(bs, job->sync_bitmap, NULL); assert(bm); } } static void backup_commit(BlockJob *job) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); if (s->sync_bitmap) { backup_cleanup_sync_bitmap(s, 0); } } static void backup_abort(BlockJob *job) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); if (s->sync_bitmap) { backup_cleanup_sync_bitmap(s, -1); } } static void backup_attached_aio_context(BlockJob *job, AioContext *aio_context) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); blk_set_aio_context(s->target, aio_context); } static const BlockJobDriver backup_job_driver = { .instance_size = sizeof(BackupBlockJob), .job_type = BLOCK_JOB_TYPE_BACKUP, .set_speed = backup_set_speed, .commit = backup_commit, .abort = backup_abort, .attached_aio_context = backup_attached_aio_context, }; static BlockErrorAction backup_error_action(BackupBlockJob *job, bool read, int error) { if (read) { return block_job_error_action(&job->common, job->on_source_error, true, error); } else { return block_job_error_action(&job->common, job->on_target_error, false, error); } } typedef struct { int ret; } BackupCompleteData; static void backup_complete(BlockJob *job, void *opaque) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); BackupCompleteData *data = opaque; blk_unref(s->target); block_job_completed(job, data->ret); g_free(data); } static bool coroutine_fn yield_and_check(BackupBlockJob *job) { if (block_job_is_cancelled(&job->common)) { return true; } /* we need to yield so that bdrv_drain_all() returns. * (without, VM does not reboot) */ if (job->common.speed) { uint64_t delay_ns = ratelimit_calculate_delay(&job->limit, job->sectors_read); job->sectors_read = 0; block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, delay_ns); } else { block_job_sleep_ns(&job->common, QEMU_CLOCK_REALTIME, 0); } if (block_job_is_cancelled(&job->common)) { return true; } return false; } static int coroutine_fn backup_run_incremental(BackupBlockJob *job) { bool error_is_read; int ret = 0; int clusters_per_iter; uint32_t granularity; int64_t sector; int64_t cluster; int64_t end; int64_t last_cluster = -1; int64_t sectors_per_cluster = cluster_size_sectors(job); HBitmapIter hbi; granularity = bdrv_dirty_bitmap_granularity(job->sync_bitmap); clusters_per_iter = MAX((granularity / job->cluster_size), 1); bdrv_dirty_iter_init(job->sync_bitmap, &hbi); /* Find the next dirty sector(s) */ while ((sector = hbitmap_iter_next(&hbi)) != -1) { cluster = sector / sectors_per_cluster; /* Fake progress updates for any clusters we skipped */ if (cluster != last_cluster + 1) { job->common.offset += ((cluster - last_cluster - 1) * job->cluster_size); } for (end = cluster + clusters_per_iter; cluster < end; cluster++) { do { if (yield_and_check(job)) { return ret; } ret = backup_do_cow(job, cluster * sectors_per_cluster, sectors_per_cluster, &error_is_read, false); if ((ret < 0) && backup_error_action(job, error_is_read, -ret) == BLOCK_ERROR_ACTION_REPORT) { return ret; } } while (ret < 0); } /* If the bitmap granularity is smaller than the backup granularity, * we need to advance the iterator pointer to the next cluster. */ if (granularity < job->cluster_size) { bdrv_set_dirty_iter(&hbi, cluster * sectors_per_cluster); } last_cluster = cluster - 1; } /* Play some final catchup with the progress meter */ end = DIV_ROUND_UP(job->common.len, job->cluster_size); if (last_cluster + 1 < end) { job->common.offset += ((end - last_cluster - 1) * job->cluster_size); } return ret; } static void coroutine_fn backup_run(void *opaque) { BackupBlockJob *job = opaque; BackupCompleteData *data; BlockDriverState *bs = blk_bs(job->common.blk); BlockBackend *target = job->target; int64_t start, end; int64_t sectors_per_cluster = cluster_size_sectors(job); int ret = 0; QLIST_INIT(&job->inflight_reqs); qemu_co_rwlock_init(&job->flush_rwlock); start = 0; end = DIV_ROUND_UP(job->common.len, job->cluster_size); job->done_bitmap = bitmap_new(end); job->before_write.notify = backup_before_write_notify; bdrv_add_before_write_notifier(bs, &job->before_write); if (job->sync_mode == MIRROR_SYNC_MODE_NONE) { while (!block_job_is_cancelled(&job->common)) { /* Yield until the job is cancelled. We just let our before_write * notify callback service CoW requests. */ block_job_yield(&job->common); } } else if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { ret = backup_run_incremental(job); } else { /* Both FULL and TOP SYNC_MODE's require copying.. */ for (; start < end; start++) { bool error_is_read; if (yield_and_check(job)) { break; } if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { int i, n; int alloced = 0; /* Check to see if these blocks are already in the * backing file. */ for (i = 0; i < sectors_per_cluster;) { /* bdrv_is_allocated() only returns true/false based * on the first set of sectors it comes across that * are are all in the same state. * For that reason we must verify each sector in the * backup cluster length. We end up copying more than * needed but at some point that is always the case. */ alloced = bdrv_is_allocated(bs, start * sectors_per_cluster + i, sectors_per_cluster - i, &n); i += n; if (alloced == 1 || n == 0) { break; } } /* If the above loop never found any sectors that are in * the topmost image, skip this backup. */ if (alloced == 0) { continue; } } /* FULL sync mode we copy the whole drive. */ ret = backup_do_cow(job, start * sectors_per_cluster, sectors_per_cluster, &error_is_read, false); if (ret < 0) { /* Depending on error action, fail now or retry cluster */ BlockErrorAction action = backup_error_action(job, error_is_read, -ret); if (action == BLOCK_ERROR_ACTION_REPORT) { break; } else { start--; continue; } } } } notifier_with_return_remove(&job->before_write); /* wait until pending backup_do_cow() calls have completed */ qemu_co_rwlock_wrlock(&job->flush_rwlock); qemu_co_rwlock_unlock(&job->flush_rwlock); g_free(job->done_bitmap); bdrv_op_unblock_all(blk_bs(target), job->common.blocker); data = g_malloc(sizeof(*data)); data->ret = ret; block_job_defer_to_main_loop(&job->common, backup_complete, data); } void backup_start(BlockDriverState *bs, BlockDriverState *target, int64_t speed, MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, BlockdevOnError on_source_error, BlockdevOnError on_target_error, BlockCompletionFunc *cb, void *opaque, BlockJobTxn *txn, Error **errp) { int64_t len; BlockDriverInfo bdi; BackupBlockJob *job = NULL; int ret; assert(bs); assert(target); if (bs == target) { error_setg(errp, "Source and target cannot be the same"); return; } if (!bdrv_is_inserted(bs)) { error_setg(errp, "Device is not inserted: %s", bdrv_get_device_name(bs)); return; } if (!bdrv_is_inserted(target)) { error_setg(errp, "Device is not inserted: %s", bdrv_get_device_name(target)); return; } if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) { return; } if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) { return; } if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { if (!sync_bitmap) { error_setg(errp, "must provide a valid bitmap name for " "\"incremental\" sync mode"); return; } /* Create a new bitmap, and freeze/disable this one. */ if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) { return; } } else if (sync_bitmap) { error_setg(errp, "a sync_bitmap was provided to backup_run, " "but received an incompatible sync_mode (%s)", MirrorSyncMode_lookup[sync_mode]); return; } len = bdrv_getlength(bs); if (len < 0) { error_setg_errno(errp, -len, "unable to get length for '%s'", bdrv_get_device_name(bs)); goto error; } job = block_job_create(NULL, &backup_job_driver, bs, speed, cb, opaque, errp); if (!job) { goto error; } job->target = blk_new(); blk_insert_bs(job->target, target); job->on_source_error = on_source_error; job->on_target_error = on_target_error; job->sync_mode = sync_mode; job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ? sync_bitmap : NULL; /* If there is no backing file on the target, we cannot rely on COW if our * backup cluster size is smaller than the target cluster size. Even for * targets with a backing file, try to avoid COW if possible. */ ret = bdrv_get_info(target, &bdi); if (ret < 0 && !target->backing) { error_setg_errno(errp, -ret, "Couldn't determine the cluster size of the target image, " "which has no backing file"); error_append_hint(errp, "Aborting, since this may create an unusable destination image\n"); goto error; } else if (ret < 0 && target->backing) { /* Not fatal; just trudge on ahead. */ job->cluster_size = BACKUP_CLUSTER_SIZE_DEFAULT; } else { job->cluster_size = MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size); } bdrv_op_block_all(target, job->common.blocker); job->common.len = len; job->common.co = qemu_coroutine_create(backup_run); block_job_txn_add_job(txn, &job->common); qemu_coroutine_enter(job->common.co, job); return; error: if (sync_bitmap) { bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL); } if (job) { blk_unref(job->target); block_job_unref(&job->common); } }