[Qemu-devel] [PATCH] migration: adding migration to/from a file

[Uri Lublin <uril@redhat.com>]

Migration to file, reuses migration-to-fd.
Migration from file, uses qemu-fopen directly.

The saved state-file should be used only once and removed (or used
with -snapshot, or a the disk-image should be copied), as the
disk image is not saved, only the VM state.

Also there is not point of doing a _live_ migration to file (except
for debugging migration code), so I recommend to stop the VM before 
migrating its state to a file.

An advantage migration-to-file over savevm/loadvm is that for the latter
a qcow2 is a requirement, while the former works for any image-format.

Signed-off-by: Uri Lublin <uril@redhat.com>
---
 Makefile         |    2 +-
 migration-file.c |  127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 migration.c      |    4 ++
 migration.h      |    5 ++
 4 files changed, 137 insertions(+), 1 deletions(-)
 create mode 100644 migration-file.c

diff --git a/Makefile b/Makefile
index 8cbdcda..7e0e6f2 100644
--- a/Makefile
+++ b/Makefile
@@ -81,7 +81,7 @@ OBJS+=usb.o usb-hub.o usb-$(HOST_USB).o usb-hid.o usb-msd.o usb-wacom.o
 OBJS+=usb-serial.o usb-net.o
 OBJS+=sd.o ssi-sd.o
 OBJS+=bt.o bt-host.o bt-vhci.o bt-l2cap.o bt-sdp.o bt-hci.o bt-hid.o usb-bt.o
-OBJS+=buffered_file.o migration.o migration-tcp.o net.o qemu-sockets.o
+OBJS+=buffered_file.o migration.o migration-tcp.o migration-file.o net.o qemu-sockets.o
 OBJS+=qemu-char.o aio.o net-checksum.o savevm.o cache-utils.o
 
 ifdef CONFIG_BRLAPI
diff --git a/migration-file.c b/migration-file.c
new file mode 100644
index 0000000..5cde3e2
--- /dev/null
+++ b/migration-file.c
@@ -0,0 +1,127 @@
+/*
+ * QEMU live migration
+ *
+ * Copyright IBM, Corp. 2008
+ *           Red Hat, Inc. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Uri Lublin        <uril@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <unistd.h>
+#include "qemu-common.h"
+#include "migration.h"
+#include "sysemu.h"
+#include "console.h"
+#include "block.h"
+
+//#define DEBUG_MIGRATION_FILE
+
+#ifdef DEBUG_MIGRATION_FILE
+#define dprintf(fmt, ...) \
+    do { printf("migration-file: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) \
+    do { } while (0)
+#endif
+
+static int file_close(FdMigrationState *s)
+{
+    close(s->fd);
+}
+
+static int file_errno(FdMigrationState *s)
+{
+    return errno;
+}
+
+static int file_write(FdMigrationState *s, const void * buf, size_t size)
+{
+    return write(s->fd, buf, size);
+}
+
+MigrationState *file_start_outgoing_migration(const char *filename,
+                                              int64_t bandwidth_limit,
+                                              int async)
+{
+    FdMigrationState *s;
+    int fd;
+
+    s = qemu_mallocz(sizeof(*s));
+    if (s == NULL) {
+        perror("file_migration: qemu_mallocz failed");
+        term_printf("file_migration: qemu_mallocz failed");
+        goto err1;
+    }
+
+    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fd < 0) {
+        perror("file_migration: failed to open filename");
+        term_printf("file_migration: failed to open filename %s\n", filename);
+        goto err2;
+    }
+
+    s->fd = fd;
+    s->close = file_close;
+    s->get_error = file_errno;
+    s->write = file_write;
+    s->mig_state.cancel = migrate_fd_cancel;
+    s->mig_state.get_status = migrate_fd_get_status;
+    s->mig_state.release = migrate_fd_release;
+
+    s->state = MIG_STATE_ACTIVE;
+    s->detach = !async;
+    s->bandwidth_limit = bandwidth_limit;
+
+    if (s->detach == 1) {
+        dprintf("detaching from monitor\n");
+        monitor_suspend();
+        s->detach = 2;
+    }
+
+    migrate_fd_connect(s);
+    return &s->mig_state;
+
+err1:
+    close(fd);
+    unlink(filename);
+err2:
+    qemu_free(s);
+
+    return NULL;
+}
+
+int file_start_incoming_migration(const char *filename)
+{
+    int ret;
+    QEMUFile *f;
+
+    dprintf("Starting incoming file migration from '%s'\n", filename);
+    f = qemu_fopen(filename, "rb");
+    if(f == NULL) {
+        perror("failed to open file");
+        term_printf("failed to open file %s\n", filename);
+        return -errno;
+    }
+
+    vm_stop(0); /* just in case */
+    ret = qemu_loadvm_state(f);
+    if (ret < 0) {
+        fprintf(stderr, "in_file_mig: load of migration failed\n");
+        goto err;
+    }
+    qemu_announce_self();
+    dprintf("successfully loaded vm state\n");
+    vm_start();
+    qemu_fclose(f);
+    return 0;
+
+err:
+    qemu_fclose(f);
+    return -errno;
+}
diff --git a/migration.c b/migration.c
index 0ef777a..0dde557 100644
--- a/migration.c
+++ b/migration.c
@@ -44,6 +44,8 @@ void qemu_start_incoming_migration(const char *uri)
     else if (strstart(uri, "exec:", &p))
         exec_start_incoming_migration(p);
 #endif
+    else if (strstart(uri, "file:", &p))
+        file_start_incoming_migration(p);
     else
         fprintf(stderr, "unknown migration protocol: %s\n", uri);
 }
@@ -59,6 +61,8 @@ void do_migrate(int detach, const char *uri)
     else if (strstart(uri, "exec:", &p))
         s = exec_start_outgoing_migration(p, max_throttle, detach);
 #endif
+    else if (strstart(uri, "file:", &p))
+        s = file_start_outgoing_migration(p, (1<<31), detach);
     else
         term_printf("unknown migration protocol: %s\n", uri);
 
diff --git a/migration.h b/migration.h
index d9771ad..30d4ab4 100644
--- a/migration.h
+++ b/migration.h
@@ -67,6 +67,11 @@ MigrationState *tcp_start_outgoing_migration(const char *host_port,
 					     int64_t bandwidth_limit,
 					     int detach);
 
+MigrationState *file_start_outgoing_migration(const char *filename,
+                                              int64_t bandwidth_limit,
+                                              int detach);
+int file_start_incoming_migration(const char *filename);
+
 void migrate_fd_error(FdMigrationState *s);
 
 void migrate_fd_cleanup(FdMigrationState *s);
-- 
1.6.0.6