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postcopy: Recover block devices on early failure

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An early postcopy failure can be recovered from as long as we know
we haven't sent the command to run the destination.
We have to undo the bdrv_inactivate_all by calling
bdrv_invalidate_cache_all

Note that I'm not using ms->block_inactive because once we've
sent the postcopy package we dont want anything else to try
and recover the block storage on the source; the destination
might have started writing to it.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20170202155909.31784-3-dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2017-02-02 15:59:09 +00:00 committed by Juan Quintela
parent 328d4d8528
commit ef8d6488d2
1 changed files with 25 additions and 0 deletions
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25
migration/migration.c
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@ -1601,6 +1601,7 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
QIOChannelBuffer *bioc;
QEMUFile *fb;
int64_t time_at_stop = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
bool restart_block = false;
migrate_set_state(&ms->state, MIGRATION_STATUS_ACTIVE,
MIGRATION_STATUS_POSTCOPY_ACTIVE);
@ -1620,6 +1621,7 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
if (ret < 0) {
goto fail;
}
restart_block = true;
/*
* Cause any non-postcopiable, but iterative devices to
@ -1676,6 +1678,18 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running)
/* <><> end of stuff going into the package */
/* Last point of recovery; as soon as we send the package the destination
* can open devices and potentially start running.
* Lets just check again we've not got any errors.
*/
ret = qemu_file_get_error(ms->to_dst_file);
if (ret) {
error_report("postcopy_start: Migration stream errored (pre package)");
goto fail_closefb;
}
restart_block = false;
/* Now send that blob */
if (qemu_savevm_send_packaged(ms->to_dst_file, bioc->data, bioc->usage)) {
goto fail_closefb;
@ -1713,6 +1727,17 @@ fail_closefb:
fail:
migrate_set_state(&ms->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
MIGRATION_STATUS_FAILED);
if (restart_block) {
/* A failure happened early enough that we know the destination hasn't
* accessed block devices, so we're safe to recover.
*/
Error *local_err = NULL;
bdrv_invalidate_cache_all(&local_err);
if (local_err) {
error_report_err(local_err);
}
}
qemu_mutex_unlock_iothread();
return -1;
}