1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
2 From: Stefan Reiter <s.reiter@proxmox.com>
3 Date: Thu, 20 Aug 2020 14:25:00 +0200
4 Subject: [PATCH] PVE-Backup: Use a transaction to synchronize job states
6 By using a JobTxn, we can sync dirty bitmaps only when *all* jobs were
7 successful - meaning we don't need to remove them when the backup fails,
8 since QEMU's BITMAP_SYNC_MODE_ON_SUCCESS will now handle that for us.
10 To keep the rate-limiting and IO impact from before, we use a sequential
11 transaction, so drives will still be backed up one after the other.
13 Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
15 pve-backup.c | 167 +++++++++++++++------------------------------------
16 1 file changed, 49 insertions(+), 118 deletions(-)
18 diff --git a/pve-backup.c b/pve-backup.c
19 index 2db4a62580..b52f4a9364 100644
22 @@ -52,6 +52,7 @@ static struct PVEBackupState {
24 ProxmoxBackupHandle *pbs;
27 QemuMutex backup_mutex;
28 CoMutex dump_callback_mutex;
30 @@ -71,32 +72,12 @@ typedef struct PVEBackupDevInfo {
35 char targetfile[PATH_MAX];
36 BdrvDirtyBitmap *bitmap;
37 BlockDriverState *target;
41 -static void pvebackup_run_next_job(void);
44 -lookup_active_block_job(PVEBackupDevInfo *di)
46 - if (!di->completed && di->bs) {
47 - for (BlockJob *job = block_job_next(NULL); job; job = block_job_next(job)) {
48 - if (job->job.driver->job_type != JOB_TYPE_BACKUP) {
52 - BackupBlockJob *bjob = container_of(job, BackupBlockJob, common);
53 - if (bjob && bjob->source_bs == di->bs) {
61 static void pvebackup_propagate_error(Error *err)
63 qemu_mutex_lock(&backup_state.stat.lock);
64 @@ -272,18 +253,6 @@ static void coroutine_fn pvebackup_co_cleanup(void *unused)
65 if (local_err != NULL) {
66 pvebackup_propagate_error(local_err);
69 - // on error or cancel we cannot ensure synchronization of dirty
70 - // bitmaps with backup server, so remove all and do full backup next
71 - GList *l = backup_state.di_list;
73 - PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
77 - bdrv_release_dirty_bitmap(di->bitmap);
82 proxmox_backup_disconnect(backup_state.pbs);
83 @@ -322,8 +291,6 @@ static void pvebackup_complete_cb(void *opaque, int ret)
85 qemu_mutex_lock(&backup_state.backup_mutex);
87 - di->completed = true;
90 Error *local_err = NULL;
91 error_setg(&local_err, "job failed with err %d - %s", ret, strerror(-ret));
92 @@ -336,20 +303,17 @@ static void pvebackup_complete_cb(void *opaque, int ret)
94 block_on_coroutine_fn(pvebackup_complete_stream, di);
96 - // remove self from job queue
97 + // remove self from job list
98 backup_state.di_list = g_list_remove(backup_state.di_list, di);
100 - if (di->bitmap && ret < 0) {
101 - // on error or cancel we cannot ensure synchronization of dirty
102 - // bitmaps with backup server, so remove all and do full backup next
103 - bdrv_release_dirty_bitmap(di->bitmap);
108 - qemu_mutex_unlock(&backup_state.backup_mutex);
109 + /* call cleanup if we're the last job */
110 + if (!g_list_first(backup_state.di_list)) {
111 + block_on_coroutine_fn(pvebackup_co_cleanup, NULL);
114 - pvebackup_run_next_job();
115 + qemu_mutex_unlock(&backup_state.backup_mutex);
118 static void pvebackup_cancel(void)
119 @@ -371,36 +335,28 @@ static void pvebackup_cancel(void)
120 proxmox_backup_abort(backup_state.pbs, "backup canceled");
123 - qemu_mutex_unlock(&backup_state.backup_mutex);
127 - BlockJob *next_job = NULL;
129 - qemu_mutex_lock(&backup_state.backup_mutex);
131 - GList *l = backup_state.di_list;
133 - PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
134 - l = g_list_next(l);
135 + /* it's enough to cancel one job in the transaction, the rest will follow
137 + GList *bdi = g_list_first(backup_state.di_list);
138 + BlockJob *cancel_job = bdi && bdi->data ?
139 + ((PVEBackupDevInfo *)bdi->data)->job :
142 - BlockJob *job = lookup_active_block_job(di);
148 + /* ref the job before releasing the mutex, just to be safe */
150 + job_ref(&cancel_job->job);
153 - qemu_mutex_unlock(&backup_state.backup_mutex);
154 + /* job_cancel_sync may enter the job, so we need to release the
155 + * backup_mutex to avoid deadlock */
156 + qemu_mutex_unlock(&backup_state.backup_mutex);
159 - AioContext *aio_context = next_job->job.aio_context;
160 - aio_context_acquire(aio_context);
161 - job_cancel_sync(&next_job->job);
162 - aio_context_release(aio_context);
167 + AioContext *aio_context = cancel_job->job.aio_context;
168 + aio_context_acquire(aio_context);
169 + job_cancel_sync(&cancel_job->job);
170 + job_unref(&cancel_job->job);
171 + aio_context_release(aio_context);
175 @@ -459,51 +415,19 @@ static int coroutine_fn pvebackup_co_add_config(
179 -bool job_should_pause(Job *job);
181 -static void pvebackup_run_next_job(void)
183 - assert(!qemu_in_coroutine());
185 - qemu_mutex_lock(&backup_state.backup_mutex);
187 - GList *l = backup_state.di_list;
189 - PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
190 - l = g_list_next(l);
192 - BlockJob *job = lookup_active_block_job(di);
195 - qemu_mutex_unlock(&backup_state.backup_mutex);
197 - AioContext *aio_context = job->job.aio_context;
198 - aio_context_acquire(aio_context);
200 - if (job_should_pause(&job->job)) {
201 - bool error_or_canceled = pvebackup_error_or_canceled();
202 - if (error_or_canceled) {
203 - job_cancel_sync(&job->job);
205 - job_resume(&job->job);
208 - aio_context_release(aio_context);
213 - block_on_coroutine_fn(pvebackup_co_cleanup, NULL); // no more jobs, run cleanup
215 - qemu_mutex_unlock(&backup_state.backup_mutex);
218 static bool create_backup_jobs(void) {
220 assert(!qemu_in_coroutine());
222 Error *local_err = NULL;
224 + /* create job transaction to synchronize bitmap commit and cancel all
225 + * jobs in case one errors */
226 + if (backup_state.txn) {
227 + job_txn_unref(backup_state.txn);
229 + backup_state.txn = job_txn_new_seq();
231 /* create and start all jobs (paused state) */
232 GList *l = backup_state.di_list;
234 @@ -524,7 +448,7 @@ static bool create_backup_jobs(void) {
235 BlockJob *job = backup_job_create(
236 NULL, di->bs, di->target, backup_state.speed, sync_mode, di->bitmap,
237 bitmap_mode, false, NULL, BLOCKDEV_ON_ERROR_REPORT, BLOCKDEV_ON_ERROR_REPORT,
238 - JOB_DEFAULT, pvebackup_complete_cb, di, 1, NULL, &local_err);
239 + JOB_DEFAULT, pvebackup_complete_cb, di, backup_state.txn, &local_err);
241 aio_context_release(aio_context);
243 @@ -536,7 +460,8 @@ static bool create_backup_jobs(void) {
244 pvebackup_propagate_error(create_job_err);
247 - job_start(&job->job);
251 bdrv_unref(di->target);
253 @@ -554,6 +479,10 @@ static bool create_backup_jobs(void) {
254 bdrv_unref(di->target);
259 + job_unref(&di->job->job);
264 @@ -944,10 +873,6 @@ err:
265 PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
269 - bdrv_release_dirty_bitmap(di->bitmap);
273 bdrv_unref(di->target);
275 @@ -1036,9 +961,15 @@ UuidInfo *qmp_backup(
276 block_on_coroutine_fn(pvebackup_co_prepare, &task);
279 - create_backup_jobs();
280 + bool errors = create_backup_jobs();
281 qemu_mutex_unlock(&backup_state.backup_mutex);
282 - pvebackup_run_next_job();
285 + /* start the first job in the transaction
286 + * note: this might directly enter the job, so we need to do this
287 + * after unlocking the backup_mutex */
288 + job_txn_start_seq(backup_state.txn);
291 qemu_mutex_unlock(&backup_state.backup_mutex);