[RFC PATCH v1 01/26] migration: Add support for 'file:' uri for source migration

[Fabiano Rosas]

From: Nikolay Borisov <nborisov@suse.com>

Implement support for a "file:" uri so that a migration can be initiated
directly to a file from QEMU.

Unlike other migration protocol backends, the 'file' protocol cannot
honour non-blocking mode. POSIX file/block storage will always report
ready to read/write, regardless of how slow the underlying storage
will be at servicing the request.

For outgoing migration this limitation is not a serious problem as
the migration data transfer always happens in a dedicated thread.
It may, however, result in delays in honouring a request to cancel
the migration operation.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/file.c      | 21 +++++++++++++++++++++
 migration/file.h      |  9 +++++++++
 migration/meson.build |  1 +
 migration/migration.c |  3 +++
 4 files changed, 34 insertions(+)
 create mode 100644 migration/file.c
 create mode 100644 migration/file.h

diff --git a/migration/file.c b/migration/file.c
new file mode 100644
index 0000000000..36d6178c75
--- /dev/null
+++ b/migration/file.c
@@ -0,0 +1,21 @@
+#include "qemu/osdep.h"
+#include "channel.h"
+#include "io/channel-file.h"
+#include "file.h"
+#include "qemu/error-report.h"
+
+
+void file_start_outgoing_migration(MigrationState *s, const char *fname, Error 
**errp)
+{
+    QIOChannelFile *ioc;
+
+    ioc = qio_channel_file_new_path(fname, O_CREAT | O_TRUNC | O_WRONLY, 0660, 
errp);
+    if (!ioc) {
+        error_report("Error creating a channel");
+        return;
+    }
+
+    qio_channel_set_name(QIO_CHANNEL(ioc), "migration-file-outgoing");
+    migration_channel_connect(s, QIO_CHANNEL(ioc), NULL, NULL);
+    object_unref(OBJECT(ioc));
+}
diff --git a/migration/file.h b/migration/file.h
new file mode 100644
index 0000000000..d476eb1157
--- /dev/null
+++ b/migration/file.h
@@ -0,0 +1,9 @@
+#ifndef QEMU_MIGRATION_FILE_H
+#define QEMU_MIGRATION_FILE_H
+
+void file_start_outgoing_migration(MigrationState *s,
+                                   const char *filename,
+                                   Error **errp);
+
+#endif
+
diff --git a/migration/meson.build b/migration/meson.build
index 0d1bb9f96e..6c02298c70 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -17,6 +17,7 @@ softmmu_ss.add(files(
   'colo.c',
   'exec.c',
   'fd.c',
+  'file.c',
   'global_state.c',
   'migration-hmp-cmds.c',
   'migration.c',
diff --git a/migration/migration.c b/migration/migration.c
index ae2025d9d8..58ff0cb7c7 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -20,6 +20,7 @@
 #include "migration/blocker.h"
 #include "exec.h"
 #include "fd.h"
+#include "file.h"
 #include "socket.h"
 #include "sysemu/runstate.h"
 #include "sysemu/sysemu.h"
@@ -2523,6 +2524,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         exec_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_outgoing_migration(s, p, &local_err);
+    } else if (strstart(uri, "file:", &p)) {
+        file_start_outgoing_migration(s, p, &local_err);
     } else {
         if (!(has_resume && resume)) {
             yank_unregister_instance(MIGRATION_YANK_INSTANCE);
-- 
2.35.3