migration/multifd: Add outgoing QIOChannelFile support

Allow multifd to open file-backed channels. This will be used when
enabling the mapped-ram migration stream format which expects a
seekable transport.

The QIOChannel read and write methods will use the preadv/pwritev
versions which don't update the file offset at each call so we can
reuse the fd without re-opening for every channel.

Contrary to the socket migration, the file migration doesn't need an
asynchronous channel creation process, so expose
multifd_channel_connect() and call it directly.

Note that this is just setup code and multifd cannot yet make use of
the file channels.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/20240229153017.2221-18-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/migration/file.h b/migration/file.h
index 37d6a08bfc..4577f9efdd 100644
--- a/migration/file.h
+++ b/migration/file.h
@@ -9,10 +9,14 @@
 #define QEMU_MIGRATION_FILE_H
 
 #include "qapi/qapi-types-migration.h"
+#include "io/task.h"
+#include "channel.h"
 
 void file_start_incoming_migration(FileMigrationArgs *file_args, Error **errp);
 
 void file_start_outgoing_migration(MigrationState *s,
                                    FileMigrationArgs *file_args, Error **errp);
 int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp);
+void file_cleanup_outgoing_migration(void);
+bool file_send_channel_create(gpointer opaque, Error **errp);
 #endif