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migration: Enlarge postcopy recovery to capture !-EIO too

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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.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220301083925.33483-11-peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Peter Xu 2022-03-01 16:39:10 +08:00 committed by Dr. David Alan Gilbert
parent 755e8d7cb6
commit d5c8f2afe8
2 changed files with 3 additions and 3 deletions
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4
migration/migration.c
View File

@ -2865,7 +2865,7 @@ 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.
@ -3466,7 +3466,7 @@ 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

2
migration/postcopy-ram.c
View File

@ -1039,7 +1039,7 @@ 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 {