/* * 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_int.h" #include "block/block_backup.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" #include "qemu/error-report.h" #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16) typedef struct BackupBlockJob { BlockJob common; BlockBackend *target; /* bitmap for sync=incremental */ BdrvDirtyBitmap *sync_bitmap; MirrorSyncMode sync_mode; BlockdevOnError on_source_error; BlockdevOnError on_target_error; CoRwlock flush_rwlock; uint64_t len; uint64_t bytes_read; int64_t cluster_size; bool compress; NotifierWithReturn before_write; QLIST_HEAD(, CowRequest) inflight_reqs; HBitmap *copy_bitmap; } BackupBlockJob; static const BlockJobDriver backup_job_driver; /* 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_byte && start < req->end_byte) { qemu_co_queue_wait(&req->wait_queue, NULL); 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_byte = start; req->end_byte = 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 offset, uint64_t bytes, 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 start, end; /* bytes */ int n; /* bytes */ qemu_co_rwlock_rdlock(&job->flush_rwlock); start = QEMU_ALIGN_DOWN(offset, job->cluster_size); end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size); trace_backup_do_cow_enter(job, start, offset, bytes); wait_for_overlapping_requests(job, start, end); cow_request_begin(&cow_request, job, start, end); for (; start < end; start += job->cluster_size) { if (!hbitmap_get(job->copy_bitmap, start / job->cluster_size)) { trace_backup_do_cow_skip(job, start); continue; /* already copied */ } hbitmap_reset(job->copy_bitmap, start / job->cluster_size, 1); trace_backup_do_cow_process(job, start); n = MIN(job->cluster_size, job->len - start); if (!bounce_buffer) { bounce_buffer = blk_blockalign(blk, job->cluster_size); } iov.iov_base = bounce_buffer; iov.iov_len = n; qemu_iovec_init_external(&bounce_qiov, &iov, 1); ret = blk_co_preadv(blk, start, 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; } hbitmap_set(job->copy_bitmap, start / job->cluster_size, 1); goto out; } if (buffer_is_zero(iov.iov_base, iov.iov_len)) { ret = blk_co_pwrite_zeroes(job->target, start, bounce_qiov.size, BDRV_REQ_MAY_UNMAP); } else { ret = blk_co_pwritev(job->target, start, bounce_qiov.size, &bounce_qiov, job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0); } if (ret < 0) { trace_backup_do_cow_write_fail(job, start, ret); if (error_is_read) { *error_is_read = false; } hbitmap_set(job->copy_bitmap, start / job->cluster_size, 1); goto out; } /* 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->bytes_read += n; block_job_progress_update(&job->common, n); } out: if (bounce_buffer) { qemu_vfree(bounce_buffer); } cow_request_end(&cow_request); trace_backup_do_cow_return(job, offset, bytes, 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; assert(req->bs == blk_bs(job->common.blk)); assert(QEMU_IS_ALIGNED(req->offset, BDRV_SECTOR_SIZE)); assert(QEMU_IS_ALIGNED(req->bytes, BDRV_SECTOR_SIZE)); return backup_do_cow(job, req->offset, req->bytes, NULL, true); } static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret) { BdrvDirtyBitmap *bm; BlockDriverState *bs = blk_bs(job->common.blk); if (ret < 0) { /* 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_clean(BlockJob *job) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); assert(s->target); blk_unref(s->target); s->target = NULL; } 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); } void backup_do_checkpoint(BlockJob *job, Error **errp) { BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); int64_t len; assert(block_job_driver(job) == &backup_job_driver); if (backup_job->sync_mode != MIRROR_SYNC_MODE_NONE) { error_setg(errp, "The backup job only supports block checkpoint in" " sync=none mode"); return; } len = DIV_ROUND_UP(backup_job->len, backup_job->cluster_size); hbitmap_set(backup_job->copy_bitmap, 0, len); } void backup_wait_for_overlapping_requests(BlockJob *job, int64_t offset, uint64_t bytes) { BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); int64_t start, end; assert(block_job_driver(job) == &backup_job_driver); start = QEMU_ALIGN_DOWN(offset, backup_job->cluster_size); end = QEMU_ALIGN_UP(offset + bytes, backup_job->cluster_size); wait_for_overlapping_requests(backup_job, start, end); } void backup_cow_request_begin(CowRequest *req, BlockJob *job, int64_t offset, uint64_t bytes) { BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common); int64_t start, end; assert(block_job_driver(job) == &backup_job_driver); start = QEMU_ALIGN_DOWN(offset, backup_job->cluster_size); end = QEMU_ALIGN_UP(offset + bytes, backup_job->cluster_size); cow_request_begin(req, backup_job, start, end); } void backup_cow_request_end(CowRequest *req) { cow_request_end(req); } static void backup_drain(BlockJob *job) { BackupBlockJob *s = container_of(job, BackupBlockJob, common); /* Need to keep a reference in case blk_drain triggers execution * of backup_complete... */ if (s->target) { BlockBackend *target = s->target; blk_ref(target); blk_drain(target); blk_unref(target); } } 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) { BackupCompleteData *data = opaque; block_job_completed(job, data->ret); g_free(data); } static bool coroutine_fn yield_and_check(BackupBlockJob *job) { uint64_t delay_ns; if (block_job_is_cancelled(&job->common)) { return true; } /* We need to yield even for delay_ns = 0 so that bdrv_drain_all() can * return. Without a yield, the VM would not reboot. */ delay_ns = block_job_ratelimit_get_delay(&job->common, job->bytes_read); job->bytes_read = 0; block_job_sleep_ns(&job->common, delay_ns); if (block_job_is_cancelled(&job->common)) { return true; } return false; } static int coroutine_fn backup_run_incremental(BackupBlockJob *job) { int ret; bool error_is_read; int64_t cluster; HBitmapIter hbi; hbitmap_iter_init(&hbi, job->copy_bitmap, 0); while ((cluster = hbitmap_iter_next(&hbi)) != -1) { do { if (yield_and_check(job)) { return 0; } ret = backup_do_cow(job, cluster * job->cluster_size, job->cluster_size, &error_is_read, false); if (ret < 0 && backup_error_action(job, error_is_read, -ret) == BLOCK_ERROR_ACTION_REPORT) { return ret; } } while (ret < 0); } return 0; } /* init copy_bitmap from sync_bitmap */ static void backup_incremental_init_copy_bitmap(BackupBlockJob *job) { BdrvDirtyBitmapIter *dbi; int64_t offset; int64_t end = DIV_ROUND_UP(bdrv_dirty_bitmap_size(job->sync_bitmap), job->cluster_size); dbi = bdrv_dirty_iter_new(job->sync_bitmap); while ((offset = bdrv_dirty_iter_next(dbi)) != -1) { int64_t cluster = offset / job->cluster_size; int64_t next_cluster; offset += bdrv_dirty_bitmap_granularity(job->sync_bitmap); if (offset >= bdrv_dirty_bitmap_size(job->sync_bitmap)) { hbitmap_set(job->copy_bitmap, cluster, end - cluster); break; } offset = bdrv_dirty_bitmap_next_zero(job->sync_bitmap, offset); if (offset == -1) { hbitmap_set(job->copy_bitmap, cluster, end - cluster); break; } next_cluster = DIV_ROUND_UP(offset, job->cluster_size); hbitmap_set(job->copy_bitmap, cluster, next_cluster - cluster); if (next_cluster >= end) { break; } bdrv_set_dirty_iter(dbi, next_cluster * job->cluster_size); } /* TODO block_job_progress_set_remaining() would make more sense */ block_job_progress_update(&job->common, job->len - hbitmap_count(job->copy_bitmap) * job->cluster_size); bdrv_dirty_iter_free(dbi); } static void coroutine_fn backup_run(void *opaque) { BackupBlockJob *job = opaque; BackupCompleteData *data; BlockDriverState *bs = blk_bs(job->common.blk); int64_t offset, nb_clusters; int ret = 0; QLIST_INIT(&job->inflight_reqs); qemu_co_rwlock_init(&job->flush_rwlock); nb_clusters = DIV_ROUND_UP(job->len, job->cluster_size); block_job_progress_set_remaining(&job->common, job->len); job->copy_bitmap = hbitmap_alloc(nb_clusters, 0); if (job->sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { backup_incremental_init_copy_bitmap(job); } else { hbitmap_set(job->copy_bitmap, 0, nb_clusters); } 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) { /* All bits are set in copy_bitmap to allow any cluster to be copied. * This does not actually require them to be copied. */ 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 (offset = 0; offset < job->len; offset += job->cluster_size) { bool error_is_read; int alloced = 0; if (yield_and_check(job)) { break; } if (job->sync_mode == MIRROR_SYNC_MODE_TOP) { int i; int64_t n; /* Check to see if these blocks are already in the * backing file. */ for (i = 0; i < job->cluster_size;) { /* 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, offset + i, job->cluster_size - i, &n); i += n; if (alloced || 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. */ if (alloced < 0) { ret = alloced; } else { ret = backup_do_cow(job, offset, job->cluster_size, &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 { offset -= job->cluster_size; 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); hbitmap_free(job->copy_bitmap); data = g_malloc(sizeof(*data)); data->ret = ret; block_job_defer_to_main_loop(&job->common, backup_complete, data); } static const BlockJobDriver backup_job_driver = { .instance_size = sizeof(BackupBlockJob), .job_type = BLOCK_JOB_TYPE_BACKUP, .start = backup_run, .commit = backup_commit, .abort = backup_abort, .clean = backup_clean, .attached_aio_context = backup_attached_aio_context, .drain = backup_drain, }; BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs, BlockDriverState *target, int64_t speed, MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap, bool compress, BlockdevOnError on_source_error, BlockdevOnError on_target_error, int creation_flags, 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 NULL; } if (!bdrv_is_inserted(bs)) { error_setg(errp, "Device is not inserted: %s", bdrv_get_device_name(bs)); return NULL; } if (!bdrv_is_inserted(target)) { error_setg(errp, "Device is not inserted: %s", bdrv_get_device_name(target)); return NULL; } if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) { error_setg(errp, "Compression is not supported for this drive %s", bdrv_get_device_name(target)); return NULL; } if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) { return NULL; } if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) { return NULL; } if (sync_mode == MIRROR_SYNC_MODE_INCREMENTAL) { if (!sync_bitmap) { error_setg(errp, "must provide a valid bitmap name for " "\"incremental\" sync mode"); return NULL; } /* Create a new bitmap, and freeze/disable this one. */ if (bdrv_dirty_bitmap_create_successor(bs, sync_bitmap, errp) < 0) { return NULL; } } else if (sync_bitmap) { error_setg(errp, "a sync_bitmap was provided to backup_run, " "but received an incompatible sync_mode (%s)", MirrorSyncMode_str(sync_mode)); return NULL; } 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->len is fixed, so we can't allow resize */ job = block_job_create(job_id, &backup_job_driver, txn, bs, BLK_PERM_CONSISTENT_READ, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD, speed, creation_flags, cb, opaque, errp); if (!job) { goto error; } /* The target must match the source in size, so no resize here either */ job->target = blk_new(BLK_PERM_WRITE, BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_GRAPH_MOD); ret = blk_insert_bs(job->target, target, errp); if (ret < 0) { goto error; } 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; job->compress = compress; /* 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 == -ENOTSUP && !target->backing) { /* Cluster size is not defined */ warn_report("The target block device doesn't provide " "information about the block size and it doesn't have a " "backing file. The default block size of %u bytes is " "used. If the actual block size of the target exceeds " "this default, the backup may be unusable", BACKUP_CLUSTER_SIZE_DEFAULT); job->cluster_size = BACKUP_CLUSTER_SIZE_DEFAULT; } else 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); } /* Required permissions are already taken with target's blk_new() */ block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL, &error_abort); job->len = len; return &job->common; error: if (sync_bitmap) { bdrv_reclaim_dirty_bitmap(bs, sync_bitmap, NULL); } if (job) { backup_clean(&job->common); block_job_early_fail(&job->common); } return NULL; }