migration: Revert mapped-ram multifd support to fd: URI

This reverts commit decdc76772c453ff1444612e910caa0d45cd8eac in full
and also the relevant migration-tests from
7a09f092834641b7a793d50a3a261073bbb404a6.

After the addition of the new QAPI-based migration address API in 8.2
we've been converting an "fd:" URI into a SocketAddress, missing the
fact that the "fd:" syntax could also be used for a plain file instead
of a socket. This is a problem because the SocketAddress is part of
the API, so we're effectively asking users to create a "socket"
channel to pass in a plain file.

The easiest way to fix this situation is to deprecate the usage of
both SocketAddress and "fd:" when used with a plain file for
migration. Since this has been possible since 8.2, we can wait until
9.1 to deprecate it.

For 9.0, however, we should avoid adding further support to migration
to a plain file using the old "fd:" syntax or the new SocketAddress
API, and instead require the usage of either the old-style "file:" URI
or the FileMigrationArgs::filename field of the new API with the
"/dev/fdset/NN" syntax, both of which are already supported.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240319210941.1907-1-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>

1 files changed, 5 insertions, 51 deletions

diff --git a/migration/fd.c b/migration/fd.c
index fe0d096abd..449adaa2de 100644
--- a/migration/fd.c
+++ b/migration/fd.c
@@ -15,42 +15,19 @@
  */
 
 #include "qemu/osdep.h"
-#include "qapi/error.h"
 #include "channel.h"
 #include "fd.h"
 #include "file.h"
 #include "migration.h"
 #include "monitor/monitor.h"
-#include "io/channel-file.h"
-#include "io/channel-socket.h"
 #include "io/channel-util.h"
-#include "options.h"
 #include "trace.h"
 
 
-static struct FdOutgoingArgs {
-    int fd;
-} outgoing_args;
-
-int fd_args_get_fd(void)
-{
-    return outgoing_args.fd;
-}
-
-void fd_cleanup_outgoing_migration(void)
-{
-    if (outgoing_args.fd > 0) {
-        close(outgoing_args.fd);
-        outgoing_args.fd = -1;
-    }
-}
-
 void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp)
 {
     QIOChannel *ioc;
     int fd = monitor_get_fd(monitor_cur(), fdname, errp);
-    int newfd;
-
     if (fd == -1) {
         return;
     }
@@ -62,18 +39,6 @@ void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **
         return;
     }
 
-    /*
-     * This is dup()ed just to avoid referencing an fd that might
-     * be already closed by the iochannel.
-     */
-    newfd = dup(fd);
-    if (newfd == -1) {
-        error_setg_errno(errp, errno, "Could not dup FD %d", fd);
-        object_unref(ioc);
-        return;
-    }
-    outgoing_args.fd = newfd;
-
     qio_channel_set_name(ioc, "migration-fd-outgoing");
     migration_channel_connect(s, ioc, NULL, NULL);
     object_unref(OBJECT(ioc));
@@ -104,20 +69,9 @@ void fd_start_incoming_migration(const char *fdname, Error **errp)
         return;
     }
 
-    if (migrate_multifd()) {
-        if (fd_is_socket(fd)) {
-            error_setg(errp,
-                       "Multifd migration to a socket FD is not supported");
-            object_unref(ioc);
-            return;
-        }
-
-        file_create_incoming_channels(ioc, errp);
-    } else {
-        qio_channel_set_name(ioc, "migration-fd-incoming");
-        qio_channel_add_watch_full(ioc, G_IO_IN,
-                                   fd_accept_incoming_migration,
-                                   NULL, NULL,
-                                   g_main_context_get_thread_default());
-    }
+    qio_channel_set_name(ioc, "migration-fd-incoming");
+    qio_channel_add_watch_full(ioc, G_IO_IN,
+                               fd_accept_incoming_migration,
+                               NULL, NULL,
+                               g_main_context_get_thread_default());
 }