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migration: simplify blockers

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Modify migrate_add_blocker and migrate_del_blocker to take an Error **
reason.  This allows migration to own the Error object, so that if
an error occurs in migrate_add_blocker, migration code can free the Error
and clear the client handle, simplifying client code.  It also simplifies
the migrate_del_blocker call site.

In addition, this is a pre-requisite for a proposed future patch that would
add a mode argument to migration requests to support live update, and
maintain a list of blockers for each mode.  A blocker may apply to a single
mode or to multiple modes, and passing Error** will allow one Error object
to be registered for multiple modes.

No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Tested-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Michael Galaxy <mgalaxy@akamai.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <1697634216-84215-1-git-send-email-steven.sistare@oracle.com>
This commit is contained in:
Steve Sistare 2023-10-18 06:03:36 -07:00 • committed by Juan Quintela
parent 04131e0009
commit c8a7fc5179
33 changed files with 92 additions and 150 deletions
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24
include/migration/blocker.h
View file

@ -17,19 +17,23 @@
/**
* @migrate_add_blocker - prevent migration from proceeding
*
* @reason - an error to be returned whenever migration is attempted
* @reasonp - address of an error to be returned whenever migration is attempted
*
* @errp - [out] The reason (if any) we cannot block migration right now.
*
* @returns - 0 on success, -EBUSY/-EACCES on failure, with errp set.
*
* *@reasonp is freed and set to NULL if failure is returned.
* On success, the caller must not free @reasonp, except by
* calling migrate_del_blocker.
*/
int migrate_add_blocker(Error *reason, Error **errp);
int migrate_add_blocker(Error **reasonp, Error **errp);
/**
* @migrate_add_blocker_internal - prevent migration from proceeding without
* only-migrate implications
*
* @reason - an error to be returned whenever migration is attempted
* @reasonp - address of an error to be returned whenever migration is attempted
*
* @errp - [out] The reason (if any) we cannot block migration right now.
*
@ -38,14 +42,20 @@ int migrate_add_blocker(Error *reason, Error **errp);
* Some of the migration blockers can be temporary (e.g., for a few seconds),
* so it shouldn't need to conflict with "-only-migratable". For those cases,
* we can call this function rather than @migrate_add_blocker().
*
* *@reasonp is freed and set to NULL if failure is returned.
* On success, the caller must not free @reasonp, except by
* calling migrate_del_blocker.
*/
int migrate_add_blocker_internal(Error *reason, Error **errp);
int migrate_add_blocker_internal(Error **reasonp, Error **errp);
/**
* @migrate_del_blocker - remove a blocking error from migration
* @migrate_del_blocker - remove a blocking error from migration and free it.
*
* @reason - the error blocking migration
* @reasonp - address of the error blocking migration
*
* This function frees *@reasonp and sets it to NULL.
*/
void migrate_del_blocker(Error *reason);
void migrate_del_blocker(Error **reasonp);
#endif