We consider,
- the saving of the device state (save or subsection save) and
- running the cleanup after (post_save)
as an atomic operation. And that is why, post_save() is called regardless
of whether there is a preceeding error. This means that, it is possible
that we have 2 distict errors, one from the preceeding function and the
other from the post_save() function.
This commit changes the error handling behavior when two errors occur during
a save operation.
1) Preceding errors were propagated before, but they are now dismissed, if there
is a new post_save() error.
- A failure during the main save operation, means the system failed to
reach a new desired state. A failure during the post-save cleanup,
however, is a more critical issue as it can leave the system in an
inconsistent or corrupted state. At present, all post_save() calls
succeed. However, the introduction of error handling variants of these
functions (post_save_errp) in the following commit, imply that we need
to handle and propagate these errors. Therefore, we prioritize reporting
the more severe error.
2) post_save() errors were dismissed before, but they are now propagated.
- The original design implicitly assumed post-save hooks were infallible
cleanup routines.
This will not be the case after introducing the post/pre save/load errp
variant functions. Dismissing these errors prevents users from
identifying the specific operation that failed.
The entire save-and-cleanup process is treated as a single
logical operation, and all potential failures are communicated.
Signed-off-by: Arun Menon <[email protected]>
---
migration/vmstate.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/migration/vmstate.c b/migration/vmstate.c
index
fbc59caadbbcc75fe6de27b459aa9aa25e76aa0a..ef78a1e62ad92e9608de72d125da80ea496c8dd1
100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -554,6 +554,12 @@ static int vmstate_save_dispatch(QEMUFile *f,
error_setg(errp, "Save of field %s/%s failed",
vmsd->name, field->name);
ps_ret = post_save_dispatch(vmsd, opaque, &local_err);
+ if (ps_ret) {
+ ret = ps_ret;
+ error_free_or_abort(errp);
+ error_setg(errp, "post-save for %s failed, ret: %d",
+ vmsd->name, ret);
+ }
return ret;
}
@@ -603,10 +609,14 @@ int vmstate_save_state_v(QEMUFile *f, const
VMStateDescription *vmsd,
}
ret = vmstate_subsection_save(f, vmsd, opaque, vmdesc, errp);
+
ps_ret = post_save_dispatch(vmsd, opaque, &local_err);
- if (!ret && ps_ret) {
+ if (ps_ret) {
+ if (ret) {
+ error_free_or_abort(errp);
+ }
ret = ps_ret;
- error_setg(errp, "post-save failed: %s", vmsd->name);
+ error_propagate(errp, local_err);
}
return ret;
--
2.50.1
