[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 10/20] migration: Enlarge postcopy recovery to capture !-EIO
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH 10/20] migration: Enlarge postcopy recovery to capture !-EIO too |
Date: |
Mon, 21 Feb 2022 16:15:24 +0000 |
User-agent: |
Mutt/2.1.5 (2021-12-30) |
* Peter Xu (peterx@redhat.com) wrote:
> We used to have quite a few places making sure -EIO happened and that's the
> only way to trigger postcopy recovery. That's based on the assumption that
> we'll only return -EIO for channel issues.
>
> It'll work in 99.99% cases but logically that won't cover some corner cases.
> One example is e.g. ram_block_from_stream() could fail with an interrupted
> network, then -EINVAL will be returned instead of -EIO.
>
> I remembered Dave Gilbert pointed that out before, but somehow this is
> overlooked. Neither did I encounter anything outside the -EIO error.
>
> However we'd better touch that up before it triggers a rare VM data loss
> during
> live migrating.
>
> To cover as much those cases as possible, remove the -EIO restriction on
> triggering the postcopy recovery, because even if it's not a channel failure,
> we can't do anything better than halting QEMU anyway - the corpse of the
> process may even be used by a good hand to dig out useful memory regions, or
> the admin could simply kill the process later on.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> migration/migration.c | 4 ++--
> migration/postcopy-ram.c | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index 6e4cc9cc87..67520d3105 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2877,7 +2877,7 @@ retry:
> out:
> res = qemu_file_get_error(rp);
> if (res) {
> - if (res == -EIO && migration_in_postcopy()) {
> + if (res && migration_in_postcopy()) {
> /*
> * Maybe there is something we can do: it looks like a
> * network down issue, and we pause for a recovery.
> @@ -3478,7 +3478,7 @@ static MigThrError
> migration_detect_error(MigrationState *s)
> error_free(local_error);
> }
>
> - if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret == -EIO) {
> + if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret) {
> /*
> * For postcopy, we allow the network to be down for a
> * while. After that, it can be continued by a
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index d3ec22e6de..6be510fea4 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -1038,7 +1038,7 @@ retry:
> msg.arg.pagefault.address);
> if (ret) {
> /* May be network failure, try to wait for recovery */
> - if (ret == -EIO && postcopy_pause_fault_thread(mis)) {
> + if (postcopy_pause_fault_thread(mis)) {
> /* We got reconnected somehow, try to continue */
> goto retry;
> } else {
> --
> 2.32.0
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- Re: [PATCH 04/20] migration: Introduce postcopy channels on dest node, (continued)
- [PATCH 02/20] migration: Finer grained tracepoints for POSTCOPY_LISTEN, Peter Xu, 2022/02/16
- [PATCH 05/20] migration: Dump ramblock and offset too when non-same-page detected, Peter Xu, 2022/02/16
- [PATCH 06/20] migration: Add postcopy_thread_create(), Peter Xu, 2022/02/16
- [PATCH 07/20] migration: Move static var in ram_block_from_stream() into global, Peter Xu, 2022/02/16
- [PATCH 08/20] migration: Add pss.postcopy_requested status, Peter Xu, 2022/02/16
- [PATCH 09/20] migration: Move migrate_allow_multifd and helpers into migration.c, Peter Xu, 2022/02/16
- [PATCH 10/20] migration: Enlarge postcopy recovery to capture !-EIO too, Peter Xu, 2022/02/16
- Re: [PATCH 10/20] migration: Enlarge postcopy recovery to capture !-EIO too,
Dr. David Alan Gilbert <=
- [PATCH 11/20] migration: postcopy_pause_fault_thread() never fails, Peter Xu, 2022/02/16
- [PATCH 12/20] migration: Export ram_load_postcopy(), Peter Xu, 2022/02/16
- [PATCH 13/20] migration: Move channel setup out of postcopy_try_recover(), Peter Xu, 2022/02/16
[PATCH 14/20] migration: Add migration_incoming_transport_cleanup(), Peter Xu, 2022/02/16