* zhanghailiang (zhang.zhanghaili...@huawei.com) wrote:
> commit fe904ea8242cbae2d7e69c052c754b8f5f1ba1d6 fixed a case
> which migration aborted QEMU because it didn't regain the control
> of images while some errors happened.
>
> Actually, there are another two cases can trigger the same error reports:
> " bdrv_co_do_pwritev: Assertion `!(bs->open_flags & 0x0800)' failed",
Queued.
Dave
>
> Case 1, codes path:
> migration_thread()
> migration_completion()
> bdrv_inactivate_all() ----------------> inactivate images
> qemu_savevm_state_complete_precopy()
> socket_writev_buffer() --------> error because destination fails
> qemu_fflush() ----------------> set error on migration stream
> -> qmp_migrate_cancel() ----------------> user cancelled migration
> concurrently
> -> migrate_set_state() ------------------> set migrate CANCELLIN
> migration_completion() -----------------> go on to fail_invalidate
> if (s->state == MIGRATION_STATUS_ACTIVE) -> Jump this branch
>
> Case 2, codes path:
> migration_thread()
> migration_completion()
> bdrv_inactivate_all() ----------------> inactivate images
> migreation_completion() finished
> -> qmp_migrate_cancel() ---------------> user cancelled migration concurrently
> qemu_mutex_lock_iothread();
> qemu_bh_schedule (s->cleanup_bh);
>
> As we can see from above, qmp_migrate_cancel can slip in whenever
> migration_thread does not hold the global lock. If this happens after
> bdrv_inactive_all() been called, the above error reports will appear.
>
> To prevent this, we can call bdrv_invalidate_cache_all() in
> qmp_migrate_cancel()
> directly if we find images become inactive.
>
> Besides, bdrv_invalidate_cache_all() in migration_completion() doesn't have
> the
> protection of big lock, fix it by add the missing qemu_mutex_lock_iothread();
>
> Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
> ---
> v2:
> - Fix a bug introduced by commit fe904 which didn't get big lock
> before call bdrv_invalidate_cache_all. (Suggested by Dave)
> ---
> include/migration/migration.h | 3 +++
> migration/migration.c | 15 +++++++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index c309d23..2d5b724 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -177,6 +177,9 @@ struct MigrationState
> /* Flag set once the migration thread is running (and needs joining) */
> bool migration_thread_running;
>
> + /* Flag set once the migration thread called bdrv_inactivate_all */
> + bool block_inactive;
> +
> /* Queue of outstanding page requests from the destination */
> QemuMutex src_page_req_mutex;
> QSIMPLEQ_HEAD(src_page_requests, MigrationSrcPageRequest)
> src_page_requests;
> diff --git a/migration/migration.c b/migration/migration.c
> index f498ab8..5b50afe 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1006,6 +1006,16 @@ static void migrate_fd_cancel(MigrationState *s)
> if (s->state == MIGRATION_STATUS_CANCELLING && f) {
> qemu_file_shutdown(f);
> }
> + if (s->state == MIGRATION_STATUS_CANCELLING && s->block_inactive) {
> + Error *local_err = NULL;
> +
> + bdrv_invalidate_cache_all(&local_err);
> + if (local_err) {
> + error_report_err(local_err);
> + } else {
> + s->block_inactive = false;
> + }
> + }
> }
>
> void add_migration_state_change_notifier(Notifier *notify)
> @@ -1705,6 +1715,7 @@ static void migration_completion(MigrationState *s, int
> current_active_state,
> if (ret >= 0) {
> qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);
> qemu_savevm_state_complete_precopy(s->to_dst_file, false);
> + s->block_inactive = true;
> }
> }
> qemu_mutex_unlock_iothread();
> @@ -1755,10 +1766,14 @@ fail_invalidate:
> if (s->state == MIGRATION_STATUS_ACTIVE) {
> Error *local_err = NULL;
>
> + qemu_mutex_lock_iothread();
> bdrv_invalidate_cache_all(&local_err);
> if (local_err) {
> error_report_err(local_err);
> + } else {
> + s->block_inactive = false;
> }
> + qemu_mutex_unlock_iothread();
> }
>
> fail:
> --
> 1.8.3.1
>
>
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
