This brings async request handling and block-status driven chunk sizes to backup out of the box, which improves backup performance. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <20210116214705.822267-18-vsementsov@virtuozzo.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
560 lines
17 KiB
C
560 lines
17 KiB
C
/*
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* QEMU backup
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*
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* Copyright (C) 2013 Proxmox Server Solutions
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* Copyright (c) 2019 Virtuozzo International GmbH.
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*
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* Authors:
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* Dietmar Maurer (dietmar@proxmox.com)
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "trace.h"
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#include "block/block.h"
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#include "block/block_int.h"
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#include "block/blockjob_int.h"
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#include "block/block_backup.h"
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#include "block/block-copy.h"
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#include "qapi/error.h"
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#include "qapi/qmp/qerror.h"
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#include "qemu/cutils.h"
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#include "sysemu/block-backend.h"
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#include "qemu/bitmap.h"
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#include "qemu/error-report.h"
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#include "block/backup-top.h"
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#define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
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typedef struct BackupBlockJob {
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BlockJob common;
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BlockDriverState *backup_top;
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BlockDriverState *source_bs;
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BdrvDirtyBitmap *sync_bitmap;
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MirrorSyncMode sync_mode;
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BitmapSyncMode bitmap_mode;
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BlockdevOnError on_source_error;
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BlockdevOnError on_target_error;
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uint64_t len;
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int64_t cluster_size;
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BackupPerf perf;
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BlockCopyState *bcs;
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bool wait;
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BlockCopyCallState *bg_bcs_call;
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} BackupBlockJob;
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static const BlockJobDriver backup_job_driver;
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static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
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{
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BdrvDirtyBitmap *bm;
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bool sync = (((ret == 0) || (job->bitmap_mode == BITMAP_SYNC_MODE_ALWAYS)) \
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&& (job->bitmap_mode != BITMAP_SYNC_MODE_NEVER));
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if (sync) {
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/*
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* We succeeded, or we always intended to sync the bitmap.
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* Delete this bitmap and install the child.
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*/
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bm = bdrv_dirty_bitmap_abdicate(job->sync_bitmap, NULL);
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} else {
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/*
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* We failed, or we never intended to sync the bitmap anyway.
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* Merge the successor back into the parent, keeping all data.
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*/
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bm = bdrv_reclaim_dirty_bitmap(job->sync_bitmap, NULL);
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}
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assert(bm);
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if (ret < 0 && job->bitmap_mode == BITMAP_SYNC_MODE_ALWAYS) {
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/* If we failed and synced, merge in the bits we didn't copy: */
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bdrv_dirty_bitmap_merge_internal(bm, block_copy_dirty_bitmap(job->bcs),
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NULL, true);
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}
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}
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static void backup_commit(Job *job)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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if (s->sync_bitmap) {
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backup_cleanup_sync_bitmap(s, 0);
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}
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}
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static void backup_abort(Job *job)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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if (s->sync_bitmap) {
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backup_cleanup_sync_bitmap(s, -1);
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}
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}
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static void backup_clean(Job *job)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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bdrv_backup_top_drop(s->backup_top);
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}
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void backup_do_checkpoint(BlockJob *job, Error **errp)
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{
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BackupBlockJob *backup_job = container_of(job, BackupBlockJob, common);
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assert(block_job_driver(job) == &backup_job_driver);
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if (backup_job->sync_mode != MIRROR_SYNC_MODE_NONE) {
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error_setg(errp, "The backup job only supports block checkpoint in"
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" sync=none mode");
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return;
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}
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bdrv_set_dirty_bitmap(block_copy_dirty_bitmap(backup_job->bcs), 0,
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backup_job->len);
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}
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static BlockErrorAction backup_error_action(BackupBlockJob *job,
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bool read, int error)
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{
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if (read) {
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return block_job_error_action(&job->common, job->on_source_error,
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true, error);
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} else {
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return block_job_error_action(&job->common, job->on_target_error,
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false, error);
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}
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}
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static void coroutine_fn backup_block_copy_callback(void *opaque)
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{
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BackupBlockJob *s = opaque;
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if (s->wait) {
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s->wait = false;
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aio_co_wake(s->common.job.co);
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} else {
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job_enter(&s->common.job);
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}
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}
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static int coroutine_fn backup_loop(BackupBlockJob *job)
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{
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BlockCopyCallState *s = NULL;
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int ret = 0;
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bool error_is_read;
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BlockErrorAction act;
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while (true) { /* retry loop */
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job->bg_bcs_call = s = block_copy_async(job->bcs, 0,
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QEMU_ALIGN_UP(job->len, job->cluster_size),
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job->perf.max_workers, job->perf.max_chunk,
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backup_block_copy_callback, job);
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while (!block_copy_call_finished(s) &&
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!job_is_cancelled(&job->common.job))
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{
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job_yield(&job->common.job);
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}
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if (!block_copy_call_finished(s)) {
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assert(job_is_cancelled(&job->common.job));
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/*
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* Note that we can't use job_yield() here, as it doesn't work for
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* cancelled job.
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*/
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block_copy_call_cancel(s);
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job->wait = true;
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qemu_coroutine_yield();
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assert(block_copy_call_finished(s));
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ret = 0;
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goto out;
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}
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if (job_is_cancelled(&job->common.job) ||
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block_copy_call_succeeded(s))
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{
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ret = 0;
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goto out;
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}
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if (block_copy_call_cancelled(s)) {
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/*
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* Job is not cancelled but only block-copy call. This is possible
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* after job pause. Now the pause is finished, start new block-copy
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* iteration.
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*/
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block_copy_call_free(s);
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continue;
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}
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/* The only remaining case is failed block-copy call. */
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assert(block_copy_call_failed(s));
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ret = block_copy_call_status(s, &error_is_read);
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act = backup_error_action(job, error_is_read, -ret);
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switch (act) {
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case BLOCK_ERROR_ACTION_REPORT:
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goto out;
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case BLOCK_ERROR_ACTION_STOP:
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/*
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* Go to pause prior to starting new block-copy call on the next
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* iteration.
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*/
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job_pause_point(&job->common.job);
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break;
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case BLOCK_ERROR_ACTION_IGNORE:
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/* Proceed to new block-copy call to retry. */
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break;
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default:
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abort();
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}
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block_copy_call_free(s);
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}
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out:
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block_copy_call_free(s);
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job->bg_bcs_call = NULL;
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return ret;
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}
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static void backup_init_bcs_bitmap(BackupBlockJob *job)
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{
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bool ret;
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uint64_t estimate;
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BdrvDirtyBitmap *bcs_bitmap = block_copy_dirty_bitmap(job->bcs);
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if (job->sync_mode == MIRROR_SYNC_MODE_BITMAP) {
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ret = bdrv_dirty_bitmap_merge_internal(bcs_bitmap, job->sync_bitmap,
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NULL, true);
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assert(ret);
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} else {
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if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
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/*
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* We can't hog the coroutine to initialize this thoroughly.
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* Set a flag and resume work when we are able to yield safely.
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*/
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block_copy_set_skip_unallocated(job->bcs, true);
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}
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bdrv_set_dirty_bitmap(bcs_bitmap, 0, job->len);
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}
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estimate = bdrv_get_dirty_count(bcs_bitmap);
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job_progress_set_remaining(&job->common.job, estimate);
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}
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static int coroutine_fn backup_run(Job *job, Error **errp)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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int ret;
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backup_init_bcs_bitmap(s);
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if (s->sync_mode == MIRROR_SYNC_MODE_TOP) {
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int64_t offset = 0;
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int64_t count;
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for (offset = 0; offset < s->len; ) {
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if (job_is_cancelled(job)) {
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return -ECANCELED;
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}
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job_pause_point(job);
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if (job_is_cancelled(job)) {
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return -ECANCELED;
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}
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ret = block_copy_reset_unallocated(s->bcs, offset, &count);
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if (ret < 0) {
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return ret;
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}
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offset += count;
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}
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block_copy_set_skip_unallocated(s->bcs, false);
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}
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if (s->sync_mode == MIRROR_SYNC_MODE_NONE) {
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/*
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* All bits are set in bcs bitmap to allow any cluster to be copied.
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* This does not actually require them to be copied.
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*/
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while (!job_is_cancelled(job)) {
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/*
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* Yield until the job is cancelled. We just let our before_write
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* notify callback service CoW requests.
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*/
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job_yield(job);
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}
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} else {
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return backup_loop(s);
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}
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return 0;
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}
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static void coroutine_fn backup_pause(Job *job)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
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if (s->bg_bcs_call && !block_copy_call_finished(s->bg_bcs_call)) {
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block_copy_call_cancel(s->bg_bcs_call);
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s->wait = true;
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qemu_coroutine_yield();
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}
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}
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static void coroutine_fn backup_set_speed(BlockJob *job, int64_t speed)
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{
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BackupBlockJob *s = container_of(job, BackupBlockJob, common);
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/*
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* block_job_set_speed() is called first from block_job_create(), when we
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* don't yet have s->bcs.
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*/
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if (s->bcs) {
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block_copy_set_speed(s->bcs, speed);
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if (s->bg_bcs_call) {
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block_copy_kick(s->bg_bcs_call);
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}
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}
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}
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static const BlockJobDriver backup_job_driver = {
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.job_driver = {
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.instance_size = sizeof(BackupBlockJob),
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.job_type = JOB_TYPE_BACKUP,
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.free = block_job_free,
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.user_resume = block_job_user_resume,
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.run = backup_run,
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.commit = backup_commit,
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.abort = backup_abort,
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.clean = backup_clean,
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.pause = backup_pause,
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},
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.set_speed = backup_set_speed,
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};
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static int64_t backup_calculate_cluster_size(BlockDriverState *target,
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Error **errp)
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{
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int ret;
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BlockDriverInfo bdi;
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bool target_does_cow = bdrv_backing_chain_next(target);
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/*
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* If there is no backing file on the target, we cannot rely on COW if our
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* backup cluster size is smaller than the target cluster size. Even for
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* targets with a backing file, try to avoid COW if possible.
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*/
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ret = bdrv_get_info(target, &bdi);
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if (ret == -ENOTSUP && !target_does_cow) {
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/* Cluster size is not defined */
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warn_report("The target block device doesn't provide "
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"information about the block size and it doesn't have a "
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"backing file. The default block size of %u bytes is "
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"used. If the actual block size of the target exceeds "
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"this default, the backup may be unusable",
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BACKUP_CLUSTER_SIZE_DEFAULT);
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return BACKUP_CLUSTER_SIZE_DEFAULT;
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} else if (ret < 0 && !target_does_cow) {
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error_setg_errno(errp, -ret,
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"Couldn't determine the cluster size of the target image, "
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"which has no backing file");
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error_append_hint(errp,
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"Aborting, since this may create an unusable destination image\n");
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return ret;
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} else if (ret < 0 && target_does_cow) {
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/* Not fatal; just trudge on ahead. */
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return BACKUP_CLUSTER_SIZE_DEFAULT;
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}
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return MAX(BACKUP_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
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}
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BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
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BlockDriverState *target, int64_t speed,
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MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
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BitmapSyncMode bitmap_mode,
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bool compress,
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const char *filter_node_name,
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BackupPerf *perf,
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BlockdevOnError on_source_error,
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BlockdevOnError on_target_error,
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int creation_flags,
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BlockCompletionFunc *cb, void *opaque,
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JobTxn *txn, Error **errp)
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{
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int64_t len, target_len;
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BackupBlockJob *job = NULL;
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int64_t cluster_size;
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BdrvRequestFlags write_flags;
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BlockDriverState *backup_top = NULL;
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BlockCopyState *bcs = NULL;
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assert(bs);
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assert(target);
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/* QMP interface protects us from these cases */
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assert(sync_mode != MIRROR_SYNC_MODE_INCREMENTAL);
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assert(sync_bitmap || sync_mode != MIRROR_SYNC_MODE_BITMAP);
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if (bs == target) {
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error_setg(errp, "Source and target cannot be the same");
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return NULL;
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}
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if (!bdrv_is_inserted(bs)) {
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error_setg(errp, "Device is not inserted: %s",
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bdrv_get_device_name(bs));
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return NULL;
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}
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if (!bdrv_is_inserted(target)) {
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error_setg(errp, "Device is not inserted: %s",
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bdrv_get_device_name(target));
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return NULL;
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}
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if (compress && !bdrv_supports_compressed_writes(target)) {
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error_setg(errp, "Compression is not supported for this drive %s",
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bdrv_get_device_name(target));
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return NULL;
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}
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if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
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return NULL;
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}
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if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
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return NULL;
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}
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cluster_size = backup_calculate_cluster_size(target, errp);
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if (cluster_size < 0) {
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goto error;
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}
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if (perf->max_workers < 1) {
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error_setg(errp, "max-workers must be greater than zero");
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return NULL;
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}
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if (perf->max_chunk < 0) {
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error_setg(errp, "max-chunk must be zero (which means no limit) or "
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"positive");
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return NULL;
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}
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if (perf->max_chunk && perf->max_chunk < cluster_size) {
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error_setg(errp, "Required max-chunk (%" PRIi64 ") is less than backup "
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"cluster size (%" PRIi64 ")", perf->max_chunk, cluster_size);
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return NULL;
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}
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if (sync_bitmap) {
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/* If we need to write to this bitmap, check that we can: */
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if (bitmap_mode != BITMAP_SYNC_MODE_NEVER &&
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bdrv_dirty_bitmap_check(sync_bitmap, BDRV_BITMAP_DEFAULT, errp)) {
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return NULL;
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}
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/* Create a new bitmap, and freeze/disable this one. */
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if (bdrv_dirty_bitmap_create_successor(sync_bitmap, errp) < 0) {
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return NULL;
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}
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}
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len = bdrv_getlength(bs);
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if (len < 0) {
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error_setg_errno(errp, -len, "Unable to get length for '%s'",
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bdrv_get_device_or_node_name(bs));
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goto error;
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}
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target_len = bdrv_getlength(target);
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if (target_len < 0) {
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error_setg_errno(errp, -target_len, "Unable to get length for '%s'",
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bdrv_get_device_or_node_name(bs));
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goto error;
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}
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if (target_len != len) {
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error_setg(errp, "Source and target image have different sizes");
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goto error;
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}
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/*
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* If source is in backing chain of target assume that target is going to be
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* used for "image fleecing", i.e. it should represent a kind of snapshot of
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* source at backup-start point in time. And target is going to be read by
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* somebody (for example, used as NBD export) during backup job.
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*
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* In this case, we need to add BDRV_REQ_SERIALISING write flag to avoid
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* intersection of backup writes and third party reads from target,
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* otherwise reading from target we may occasionally read already updated by
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* guest data.
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*
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* For more information see commit f8d59dfb40bb and test
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* tests/qemu-iotests/222
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*/
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write_flags = (bdrv_chain_contains(target, bs) ? BDRV_REQ_SERIALISING : 0) |
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|
(compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
|
|
|
|
backup_top = bdrv_backup_top_append(bs, target, filter_node_name,
|
|
cluster_size, perf,
|
|
write_flags, &bcs, errp);
|
|
if (!backup_top) {
|
|
goto error;
|
|
}
|
|
|
|
/* job->len is fixed, so we can't allow resize */
|
|
job = block_job_create(job_id, &backup_job_driver, txn, backup_top,
|
|
0, BLK_PERM_ALL,
|
|
speed, creation_flags, cb, opaque, errp);
|
|
if (!job) {
|
|
goto error;
|
|
}
|
|
|
|
job->backup_top = backup_top;
|
|
job->source_bs = bs;
|
|
job->on_source_error = on_source_error;
|
|
job->on_target_error = on_target_error;
|
|
job->sync_mode = sync_mode;
|
|
job->sync_bitmap = sync_bitmap;
|
|
job->bitmap_mode = bitmap_mode;
|
|
job->bcs = bcs;
|
|
job->cluster_size = cluster_size;
|
|
job->len = len;
|
|
job->perf = *perf;
|
|
|
|
block_copy_set_progress_meter(bcs, &job->common.job.progress);
|
|
block_copy_set_speed(bcs, speed);
|
|
|
|
/* Required permissions are already taken by backup-top target */
|
|
block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL,
|
|
&error_abort);
|
|
|
|
return &job->common;
|
|
|
|
error:
|
|
if (sync_bitmap) {
|
|
bdrv_reclaim_dirty_bitmap(sync_bitmap, NULL);
|
|
}
|
|
if (backup_top) {
|
|
bdrv_backup_top_drop(backup_top);
|
|
}
|
|
|
|
return NULL;
|
|
}
|