[PATCH v4 25/34] migration/multifd: Add fixed-ram support to fd: URI

[Fabiano Rosas <farosas@suse.de>]

If we receive a file descriptor that points to a regular file, there's
nothing stopping us from doing multifd migration with fixed-ram to
that file.

Enable the fd: URI to work with multifd + fixed-ram.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/fd.c        | 30 ++++++++++++++++++++++++++++++
 migration/fd.h        |  1 +
 migration/file.c      | 12 +++++++++---
 migration/migration.c |  4 ++++
 4 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/migration/fd.c b/migration/fd.c
index 0eb677dcae..b7e4d071a4 100644
--- a/migration/fd.c
+++ b/migration/fd.c
@@ -19,14 +19,28 @@
 #include "fd.h"
 #include "migration.h"
 #include "monitor/monitor.h"
+#include "io/channel-file.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_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp)
 {
     QIOChannel *ioc;
     int fd = monitor_get_fd(monitor_cur(), fdname, errp);
+
+    outgoing_args.fd = -1;
+
     if (fd == -1) {
         return;
     }
@@ -38,6 +52,8 @@ void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **
         return;
     }
 
+    outgoing_args.fd = fd;
+
     qio_channel_set_name(ioc, "migration-fd-outgoing");
     migration_channel_connect(s, ioc, NULL, NULL);
     object_unref(OBJECT(ioc));
@@ -73,4 +89,18 @@ void fd_start_incoming_migration(const char *fdname, Error **errp)
                                fd_accept_incoming_migration,
                                NULL, NULL,
                                g_main_context_get_thread_default());
+
+    if (migrate_multifd()) {
+        int channels = migrate_multifd_channels();
+
+        while (channels--) {
+            ioc = QIO_CHANNEL(qio_channel_file_new_fd(fd));
+
+            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());
+        }
+    }
 }
diff --git a/migration/fd.h b/migration/fd.h
index b901bc014e..1be980c130 100644
--- a/migration/fd.h
+++ b/migration/fd.h
@@ -20,4 +20,5 @@ void fd_start_incoming_migration(const char *fdname, Error **errp);
 
 void fd_start_outgoing_migration(MigrationState *s, const char *fdname,
                                  Error **errp);
+int fd_args_get_fd(void);
 #endif
diff --git a/migration/file.c b/migration/file.c
index 1a18e608fc..27ccfc6a1d 100644
--- a/migration/file.c
+++ b/migration/file.c
@@ -11,6 +11,7 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "channel.h"
+#include "fd.h"
 #include "file.h"
 #include "migration.h"
 #include "io/channel-file.h"
@@ -58,10 +59,15 @@ bool file_send_channel_create(gpointer opaque, Error **errp)
 {
     QIOChannelFile *ioc;
     int flags = O_WRONLY;
+    int fd = fd_args_get_fd();
 
-    ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, errp);
-    if (!ioc) {
-        return false;
+    if (fd && fd != -1) {
+        ioc = qio_channel_file_new_fd(fd);
+    } else {
+        ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, errp);
+        if (!ioc) {
+            return false;
+        }
     }
 
     if (!multifd_channel_connect(opaque, QIO_CHANNEL(ioc), errp)) {
diff --git a/migration/migration.c b/migration/migration.c
index 32b291a282..ce7e6f5065 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -134,6 +134,10 @@ static bool transport_supports_multi_channels(MigrationAddress *addr)
     if (addr->transport == MIGRATION_ADDRESS_TYPE_SOCKET) {
         SocketAddress *saddr = &addr->u.socket;
 
+        if (saddr->type == SOCKET_ADDRESS_TYPE_FD) {
+            return migrate_fixed_ram();
+        }
+
         return (saddr->type == SOCKET_ADDRESS_TYPE_INET ||
                 saddr->type == SOCKET_ADDRESS_TYPE_UNIX ||
                 saddr->type == SOCKET_ADDRESS_TYPE_VSOCK);
-- 
2.35.3